TrueLearn CA-3 Flashcards

Question

``` What is hyperkalemic periodic paralysis? Etiology______ TRiggers______ Management__________ Treatment______ ```

Answer 1

Hyperkalemic Periodic Paralysis Etiology: mutations in sodium channel NaV1.4 Precipitated By: hyperkalemia, potassium-rich meal, rest after exercise, stressful situations, possibly hypoglycemia Anesthesia Management: avoid cholinesterase inhibitors, SCh, and potassium. Maintain normothermia and normoglycemia Treatment: glucose, insulin, epinephrine, β-agonists, and calcium **Hypothermia is associated with paralytic attacks of both hyperkalemic and hypokalemic periodic paralysis. Hypothermia leads to further impairment of the dysfunctional ion channel.

Answer 2

Serum potassium levels decrease because of transcellular shift in potassium. When beta agonists are used beta receptor are activated and intracellular cAMP levels rise and potassium is taken into cells. This transcellular shift lowers serum potassium levels, which could prevent or partially abort an attack in this patient.

Answer 3

Carboprost tromethamine is a uterotonic used to treat uterine atony after delivery of the infant(s). It produces uterine muscle contraction, rather than relaxation, and therefore may impede intrauterine fetal version or repositioning. The mechanism of action is an increase in myometrial free calcium concentration. Its use is contraindicated in patients with pulmonary hypertension and reactive airway disease, potentially causing bronchospasm, an increased intrapulmonary shunt fraction, and hypoxemia.

Answer 4

Terbutaline and nitroglycerin are used as tocolytics in an effort to halt preterm labor through uterine muscle relaxation. Terbutaline is a relatively selective beta2-receptor agonist which acts directly on uterine myometrial cells to activate adenyl cyclase, thereby decreasing intracellular calcium levels with resultant myometrial relaxation. A side effect of terbutaline is tachycardia and pulmonary edema (beta1-agonist effects), thus some practitioners currently use nitroglycerin to produce uterine muscle relaxation for fetal version, vagina delivery of a breech infant, or removal of retained placental fragments.

Answer 5

Following neurologic insult, a massive sympathetic discharge from traumatic brain injury (TBI) and intracranial hypertension can lead to neurogenic pulmonary edema (NPE). Neurogenic pulmonary edema is a relatively rare form of pulmonary edema. It typically occurs within a few hours after a neurologic insult and diagnosis requires exclusion of other causes of pulmonary edema (e.g. cardiogenic). Clinically, NPE presents with rapid onset, severe pulmonary vascular congestion, intra alveolar hemorrhage, and protein-rich edematous fluid. Treatment includes supportive care and aims at reducing intracranial hypertension. Typical treatment modalities for cardiogenic pulmonary edema are usually ineffective in treating NPE.

Answer 6

Diabetes insipidus presents with polyuria, polydipsia, hypernatremia, high serum osmolality, and dilute urine.

Answer 7

SIADH presents with hyponatremia, serum hypoosmolality, increased renal excretion of sodium, urine osmolality greater than serum osmolality, and normal renal function, and normal adrenal function.

Answer 8

Cerebral salt wasting, unlike SIADH (which presents with euvolemia and hyponatremia), presents with hypovolemia and hyponatremia

Answer 9

dP/dt (the rate of rise in ventricular pressure) is a good measure of cardiac contractility

Answer 10

Factors that can result in variable ACT include: hemodilution, hypothermia, platelet counts below 30-50 k/mL, and concomitant administration of other medications which affect platelets (e.g. prostacyclin, aspirin, glycoprotein IIb/IIIa inhibitors).

Answer 11

Certain things increase the risk of an acute exacerbation in patients with acute intermittent porphyria. These include stressful situations, prolonged fasting times, and certain medications. Trying to avoid or decrease the extent of these will help decrease the risk of exacerbation. This includes adequate hydration to decrease the risk of dehydration and supplementation with glucose to avoid starvation states. Additionally, avoidance of medications that are known to precipitate an exacerbation can help (in the perioperative period this includes barbiturates, sulfonamides, ethyl alcohol, and ergotamine).

Answer 12

The muscarinic receptors are found at the peripheral target organs. Stimulation will cause bradycardia, bronchoconstriction, miosis, salivation, gastrointestinal hypermotility and increased gastric acid secretion.

Answer 13

For generalization, the terminals in the PNS postganglionic fibers release ACh, in the SNS, NE is the principle transmitter released (except for sweat glands which use ACh).

Answer 14

Muscarinic stimulation is characterized by bradycardia, bronchoconstriction (wheezing), miosis, salivation, gastrointestinal hypermotility, and increased gastric acid secretion. Organophosphate poisoning leads to increased acetylcholine, which causes repeated receptor stimulation. Symptoms of this disorder follow muscarinic stimulation and are remembered with the mnemonic SLUDGE-Mi: salivation, lacrimation, urination, defecation, gastrointestinal upset, emesis, miosis.

Answer 15

Muscarinic receptor agonists can act through two mechanisms, directly on the muscarinic receptor or indirectly by inhibiting the breakdown of ACh causing more ACh to be available to bind to the muscarinic receptor. The direct acting agents are choline esters (ACh, methacholine, carbachol, bethanechol) or alkaloids (pilocarpine, muscarine, arecoline). Some of the direct acting agents have few clinical applications due to their very short half and longer activity can be achieved by methylating the choline moiety. The indirect acting agents are acetylcholinesterase inhibitors (physostigmine, neostigmine, pyridostigmine, edrophonium, and echothiophate). These medications are often used to improve neuromuscular function in disease states where weakness occurs such as myasthenia gravis or to help reverse the action of nondepolarizing neuromuscular blocking agents.

Answer 16

Anticholinergic drugs are used commonly in anesthesia practice. These medications inhibit the action of ACh by reversibly binding at the muscarinic receptor. Antimuscarinic drugs used in anesthesia practice are atropine, scopolamine, and glycopyrrolate. Both atropine and scopolamine cross the blood-brain barrier, which can result in inhibition of vagal outflow from the central nervous system. At low doses, vagal outflow can potentially be augmented.

Answer 17

Lidocaine crosses the placenta and may accumulate to toxic levels due to the effect of ion trapping from fetal acidosis.

Answer 18

A healthy fetus has a relatively low pH when compared to the mother. Normal fetal pH is between 7.32-7.38 while maternal pH is around 7.43 due to chronic respiratory alkalosis. In the setting of decreased uterine blood flow, such as from significant maternal blood loss, fetal pH will decrease further. The difference in pH can produce a phenomenon known as "ion trapping" that results in the accumulation of certain basic drugs in the fetus.

Answer 19

A basic drug, such as a local anesthetic, that crosses the placenta in the unionized form accepts a hydrogen ion in the more acidic environment and becomes ionized. This occurs because lidocaine has a pKa of 7.8, meaning more of the drug exists in its ionized fraction as pH decreases below 7.8. The drug can then accumulate since ionized drugs (charged, non-lipophilic) are less likely to cross over the placenta back into the maternal circulation.

Answer 20

Four main factors determine placental transfer of drugs: 1) Size: Drugs with a molecular weight < 500 Dalton's more readily cross the placenta, while drugs >1000 Dalton's do not (e.g. heparin, protamine, insulin). 2) Degree of lipid solubility: Drugs that are highly ionized do not easily cross the placenta (e.g., succinylcholine and non-depolarizing muscle relaxants). Lipophilic drugs cross readily (e.g. fentanyl). 3) Protein binding: Drugs that are highly bound to plasma proteins are less likely to cross the placenta. Unbound fractions may still cross, however, mothers have 50% more plasma proteins than the fetus and will maintain a higher concentration of protein bound drugs (e.g. bupivacaine and ropivacaine). 4) Maternal drug concentration: The higher the concentration of a drug in the maternal circulation, the greater the rate of transfer through the placenta.

Answer 21

He Is Going Nowhere Soon = Heparin, Insulin, Glycopyrrolate, Non-depolarizing muscle relaxants, Succinylcholine.

Answer 22

The inability of glycopyrrolate to cross the placenta is important to consider when reversing a pregnant woman from neuromuscular blockade. Neostigmine is also a quaternary structure but does cross the placenta to a small degree. If glycopyrrolate is administrated with neostigmine, the fetus will accordingly be exposed to more neostigmine than glycopyrrolate and can become bradycardic. For this reason, atropine may be preferred in combination with neostigmine to antagonize non-depolarizing neuromuscular blockade in pregnant patients.

Answer 23

The Malignant Hyperthermia Association of the United States (MHAUS) recommends an initial, rapid IV administration of 2.5 mg/kg of dantrolene as soon as a diagnosis of MH is suspected.

Answer 24

Normally, skeletal muscle depolarization leads to brief activation (opening) of the ryanodine-sensitive calcium channel receptor (RYR1) located on the sarcoplasmic reticulum. This causes a brief efflux of calcium that produces muscle contraction. Malignant hyperthermia-susceptible patients have RYR1 defects that, in the presence of a triggering agent (succinylcholine or any volatile anesthetic), cause prolonged opening of the channel which leads to sustained muscle contraction. This produces a generalized hypermetabolic state characterized by increased CO2, lactic acidosis, and heat production which can progress to muscle cell breakdown leading to hyperkalemia and rhabdomyolysis and their sequelae (arrhythmias; liver, kidney, and other end-organ damage; and death).

Answer 25

Dantrolene blocks calcium release from skeletal muscle sarcoplasmic reticulum by interfering with the ability of calcium and calmodulin to activate the voltage-gated ion channels (RYR1 and the L-type calcium channel).

Answer 26

It occurs because non-collapsible venous channels such as venous sinuses can be violated during surgery and air is entrapped in them due to the negative pressure gradient between the surgical site and the heart. VAEs generally travel to the heart and, if small, can be absorbed in the pulmonary vasculature. However, if large, they can cause pulmonary occlusion, increased pulmonary pressures, and even right heart failure with decreased cardiac output.

Answer 27

Vecuronium has an active metabolite, 3-desacetyl-vecuronium, that has 80% of the potency of vecuronium. Accumulation of this renally-cleared metabolite can significantly prolong the duration of action of the drug, particularly when an infusion is used in a patient with renal failure.

Answer 28

``` Wall tension (T) = (P * r) / (2 h) Where P is the pressure within the ventricle, r is the radius of the ventricle, and h is the thickness of the ventricular wall. ```

Answer 29

Multifocal atrial tachycardia (MAT) is defined by a heart rate greater than 100 and three or more distinct morphologies of the P wave on an electrocardiogram or rhythm strip. It is commonly seen in patients with pulmonary and cardiac pathologies, especially those resulting in atrial distention and pulmonary HTN. COPD exacerbation is the most common cause.

Answer 30

A LPB reliably blocks the femoral, lateral femoral cutaneous, and obturator nerves. It spares the sciatic nerve, though the commonly-used posterior approach for a LPB allows for easy access to the sciatic nerve for a separate block.

Answer 31

Celiac plexus neurolytic blocks are performed for chronic, intractable abdominal pain originating from most of the viscera. Adverse effects include hypotension, diarrhea, hiccups, pleurisy, retroperitoneal bleeding, abdominal aortic dissection, transient motor paralysis, and paraplegia.

Answer 32

The great radicular artery (aka arteria radicularis magna or artery of Adamkiewicz) originates from the aorta between the T9 and T12 vertebral segments in 75% of the population. The anterior spinal cord is perfused by a single ASA with collateralization from the radicular arteries. Interruption of the great radicular artery may result in ASA syndrome, which includes bilateral lower extremity paraplegia as well as bowel and bladder dysfunction. Sensation and proprioception are classically spared as the posterior portion of the spinal cord is supplied by two PSAs. SCPP = MAP - CSF pressure. CSF pressure is measured via a lumbar spinal drain. Arterial pressure augmentation and CSF pressure reduction are therefore the best methods by which SCPP may be optimized.

Answer 33

Carboxyhemoglobin and methemoglobin shift the oxyhemoglobin curve to the left, sulfhemoglobin to the right.

Answer 34

The active metabolite in meperidine, normeperidine, causes seizure activity. Morphine’s primary active metabolite, M6G, has a 100-fold greater potency, but exhibits an equal or decreased affinity for μ-receptors compared to morphine. Accumulation of M6G can result in respiratory depression. Morphine’s inactive metabolite, M3G, may cause myoclonus and allodynia. As morphine and meperidine metabolites are typically excreted via the kidneys, their side effects are prolonged in the setting of renal failure. Barbiturates have decreased protein binding in renal failure which leads to higher concentrations of free active molecules.

Answer 35

The ideal intensity for stimulation and successful peripheral nerve blockade is between 0.3 and 0.5 mA. Intensities less than 0.3 mA are associated with increased intraneural injections and intensities greater than 0.5 mA are often too far from the intended nerve.

Answer 36

Platelet transfusions actually carry a higher risk of TRALI compared with red blood cell transfusions. In fact they have a higher risk compared to PRBCs on all four of the following categories 1) TRALI 2) transfusion-associated sepsis 3) non-hemolytic febrile reactions and 4) allergic reactions.

Answer 37

A transversus abdominal plane block affects the intercostal, subcostal, ilioinguinal, and iliohypogastric nerves.

Answer 38

During neonatal resuscitation, positive pressure ventilation is indicated if the neonate’s heart rate drops below 100 bpm. If the heart rate falls below 60 bpm for more than 30 seconds despite adequate ventilation, chest compressions should be started. If the heart rate remains below 60 bpm despite adequate ventilation and chest compressions, epinephrine should be administered.

Answer 39

A UOSM : POSM ratio >1.5 is indicative of prerenal oliguria secondary to dehydration or hypovolemia. The UOSM : POSM evaluates the ability of the kidneys to concentrate urine and increase urine osmolality above normal plasma osmolality in the setting of prerenal oliguria.

Answer 40

Cardiac output immediately following delivery often peaks at 2.5x prepregnancy cardiac output (i.e., an increase of 150%). There is a sudden increase in preload following delivery (delivery of the baby removes some vena cava compression and uterine contraction causes autotransfusion) and less demand for blood flow to the uterus and fetus

Answer 41

ESI involves injecting steroid into the epidural space to decrease inflammation and edema of nerve roots. Nerve roots often become compressed as they leave the spinal cord by a herniated disk or spondylosis. Edema of the nerve causes increased compression and more nerve damage. Symptoms of a compressed nerve include radicular pain. Radicular pain is more likely to respond favorably to ESI than other types of back pain.

Answer 42

The oxygen saturation read by a standard two-wave pulse oximeter depends on the differential absorption of red and infrared light in tissue. Red light at 660 nm and infrared light at 940 nm (some manufacturers use 905, 910, or 920 nm) is pulsed through the tissue. A ratio of the absorbance of red to infrared light is calculated and that calculated number is translated to the oxygen saturation reading. At red wavelengths, deoxyhemoglobin absorbs more light than oxyhemoglobin; at infrared wavelengths, oxyhemoglobin absorbs more.

Answer 43

A mnemonic to help recall light absorption by wavelength is SeXy DARLing: at SiX hundred wavelength, Deoxyhemoglobin Absorbs Red Light.

Answer 44

Absolute indications for one-lung ventilation include: - Protective isolation of each lung to prevent contamination of the healthy lung: infection (e.g. abscess, infected cyst), massive hemorrhage. - Control of distribution of ventilation to only one lung: bronchopleural fistula, bronchopleural cutaneous fistula, unilateral cyst or bullae, major bronchial disruption, or trauma. - Unilateral lung lavage (e.g. pulmonary alveolar proteinosis). - Video-assisted thoracoscopic surgery (VATS).

Answer 45

``` Factors Increasing MAC: Drug - Amphetamine (acute use) - Cocaine - Ephedrine - Ethanol (chronic use) Age - Highest at age 6 months Electrolyte disturbance - Hypernatremia Hyperthermia Red hair ```

Answer 46

``` Factors Decreasing MAC: Drugs - Propofol, etomidate, barbiturates, benzodiazepines, ketamine - Alpha2 agonists (clonidine, dexmedetomidine) - Ethanol (acute use) - Local anesthetics - Opioids - Amphetamines (chronic use) - Lithium - Verapamil Age - Elderly patients Electrolyte disturbance - Hyponatremia Others - Anemia (Hgb < 5 g/dL) - Hypercarbia - Hypothermia - Hypoxia Pregnancy ```

Answer 47

Furosemide administration can cause a hypokalemic-hypochloremic metabolic alkalosis secondary to potassium excretion and a contraction alkalosis.

Answer 48

Propofol infusion syndrome is a rare complication of prolonged, high-dose propofol administration. Signs may include metabolic lactic acidosis, cardiac failure, renal failure, rhabdomyolysis, hyperkalemia, hypertriglyceridemia, hepatomegaly, and pancreatitis.

Answer 49

A sudden decrease in EtCO2 and SpO2 after tourniquet release should raise suspicion for a pulmonary embolus from a preoperative DVT.

Answer 50

The Bohr effect is a physiologic effect that describes hemoglobin’s affinity for oxygen at different conditions. During alkalotic conditions oxygen has a greater affinity for hemoglobin and during acidic conditions oxygen binds to hemoglobin less avidly. Therefore, in the lung, oxygen binds to hemoglobin with a greater affinity than when it reaches the periphery or tissues like the placenta.

Answer 51

Recurrent laryngeal

Answer 52

Pyloric stenosis commonly presents as a hypochloremic, hypokalemic, metabolic alkalosis with compensatory respiratory acidosis. Elevated serum bicarbonate is often present along with increased urine specific gravity and decreased urine chloride.

Answer 53

Ketamine is primarily a potent NMDA receptor antagonist. The NMDA receptors are a class of excitatory glutamate receptor. Ketamine does have agonist effects on the gamma-aminobutyric acid (GABA) receptor, however, this is an indirect effect via NMDA antagonism.

Answer 54

Myxedema coma is an extreme form of hypothyroidism that is classically characterized by altered mental status, hypothermia, and non-pitting edema. It is most commonly seen in patients with chronic hypothyroidism in the setting of a physiologic stressor such as infection and is considered a life threatening emergency.

Answer 55

Carbon dioxide is transported in the blood as dissolved CO2, bicarbonate, and carbamino compounds.

Answer 56

In preeclampsia, there is an elevation in thromboxane A2 levels and a decrease in prostacyclin levels leading to a primarily vasoconstricted state. Preeclampsia is characterized by global vascular hyperreactivity leading to intravascular volume depletion, high systemic vascular resistance, uterine vasoconstriction of the myometrium, and decreased uterine and placental blood flow.

Answer 57

Cyclosporine is an immunosuppressant drug that can prolong the action of NDNBDs. In addition, it has potentially neurotoxic effects, including generalized seizures, and is nephrotoxic.

Answer 58

Pudendal block provides analgesia for the 2nd stage of labor. By blocking the pudendal nerve vaginal and perineal distention pain is blocked. A paracervical block provides analgesia for the 1st stage of labor especially cervical dilation. However, paracervical blocks are associated with a high rate of fetal bradycardia. The rate of fetal bradycardia is increased if fetal acidosis is present.

Answer 59

Arterial blood gas analysis directly measures pH, PaCO2, and PaO2. Other parameters such as base excess (or deficit), bicarbonate, and SaO2 are calculated or derived from the directly-measured parameters.

Answer 60

Glycine metabolism to ammonia following absorption of glycine-containing irrigation solution during transurethral resection of the prostate (TURP) may lead to neurological complications including encephalopathy and coma lasting up to 48 hours following the procedure.

Answer 61

The term "ion trapping" refers to fetal drug accumulation due to pH differences between maternal and fetal blood, particularly in cases of fetal acidosis. Nonionized drug passes from maternal to fetal circulation. Since fetal blood pH is less than maternal blood pH, but the drug’s pKa remains constant, more of the drug will exist in the ionized form in fetal circulation. Once a local anesthetic becomes ionized in the fetus, it does not readily transfer back across the placenta to the maternal circulation.

Answer 62

The PNS is responsible for the "rest-and-digest" processes in the body, and activation of target receptors causes salivation, lacrimation, urination, digestion, and defecation. The preganglionic fibers are long compared to the SNS, and release ACh to act on nicotinic receptors. The shorter postganglionic fibers release ACh to muscarinic receptors resulting in the above effects.

Answer 63

The SNS is responsible for the “fight-or-flight response”. The preganglionic fibers are short as compared to the PNS, and release ACh to nicotinic receptors. The longer postganglionic fibers release norepinephrine (NE) to the heart and blood vessels via alpha/beta receptors, ACh to sweat glands via muscarinic receptors and dopamine to renal vessels via dopamine receptors. The adrenal glands have no postganglionic fibers, and release NE and epinephrine directly into the blood stream.

Answer 64

There are two different types of sweat glands in the body, eccrine and apocrine. Eccrine sweat glands are distributed all over the body (except for the lips, tip of penis, and clitoris), although their density varies from region to region. Humans utilize eccrine sweat glands as the primary form of cooling via sweating. They also function as a route of water and electrolyte excretion, and protection by preserving the acid mantle of the skin (skin is slightly acidic which serves as a barrier). Apocrine sweat glands are larger, have different mechanism of secretion, and are limited to armpits and perianal areas in humans. Apocrine glands contribute little to cooling in humans.

Answer 65

Anticholinergic agents interfere with the sweating mechanism, which may cause body temperature to increase (especially a child with a fever). This should be included in the differential in any patient with a fever of unknown etiology.

Answer 66

"Gentle ventilation" with permissive hypercapnia using a low tidal volume strategy, PIP < 25 cm H20, and FiO2 + PEEP adjustment to maintain preductal SpO2 of 90-95% has been shown to decrease mortality in patients with congenital diaphragmatic hernia (CDH) and is the management strategy of choice.

Answer 67

Pulmonary hypoplasia with CDH occurs as a resultant decrease in bronchiolar divisions and alveoli with thickened walls which further impair gas exchange. Alterations in pulmonary vasculature also occur with increased muscular development in smaller arterioles, decrease in the total number of vessels, and increased airway reactivity. There also appears to be an imbalance between vasodilatory (prostacyclin, NO) and vasoconstrictive (endothelin, thromboxane) mediators leading to maintenance of pulmonary hypertension. This is not to say that remodeling does not occur as thinning of the muscular layer and increased pulmonary arteriole size does occur over a process of 2-4 weeks.

Answer 68

Newer "gentle ventilation" strategies minimizing volutrauma with permissive hypercapnia and lowering peak pressures is thought to be the primary determinant of decreases in mortality associated with CDH and should be used during surgery and in the ICU. Further anesthetic management should focus on preventing elevations in pulmonary pressures, such as with hypothermia or large sympathetic outputs, and decreasing oxygen consumption in attempts to maintain oxygen balance. If sudden hypotension or hypoxia ensues, determination of the cause must be sought promptly, with two being the most common. One is contralateral pneumothorax, treated with chest tube or needle thoracostomy, and the other is worsened pulmonary hypertension, which should be treated with nitric oxide (NO).

Answer 69

The half-lives of vecuronium and pancuronium are significantly prolonged due to the accumulation of active metabolites that are renally excreted. In fact, 80% of pancuronium is renally excreted unchanged in the urine. By contrast, the half-life of rocuronium is only slightly prolonged (1.2-1.6 hours in normal patients vs. 1.6-1.7 hours in patients with end stage renal disease) since there are no active metabolites (B). There is conflicting evidence as to whether the clearance of rocuronium is slightly reduced or unaffected by renal failure. Similarly, the duration to spontaneous recovery has been reported as both similar and prolonged compared to patients without renal failure. More importantly, rocuronium is primarily excreted through the hepatobiliary system and prolonged paralysis can be seen in patients with cirrhosis and liver failure.

Answer 70

Methadone is an opioid analgesic with concurrent N-methyl-D-aspartate (NMDA) antagonistic properties, which makes it beneficial for patients with neuropathic pain. Methadone, which has good efficacy for the treatment of chronic pain, has a high oral bioavailability, high potency, and long duration of action. It also lacks active metabolites. Furthermore, the NMDA antagonism and serotonin reuptake inhibition make methadone an effective choice for chronic neuropathic pain as well as modulation of some of the psychological concerns of patients living with chronic pain.

Answer 71

Charcot-Marie-Tooth disease is a class of hereditary motor/sensory neuropathy caused by mutations in myelin and axonal genes. Most frequent manifestations include distal extremity weakness and sensory loss. Although concrete anesthetic management is hard to obtain given the limited amount of cases, caution should be taken when using neuromuscular blockade and utilizing regional anesthesia techniques.

Answer 72

Milrinone is a second generation phosphodiesterase III (PDE III) inhibitor. Both PDE I and PDE II hydrolyze all cyclic nucleotides, but PDE III acts on cAMP specifically. Milrinone, therefore, increases cAMP levels which causes its inodilator properties.

Answer 73

REduce it--it is renaly cleared

Answer 74

Common side effects of ondansetron include QTc prolongation (20%, very rarely clinically significant), headache (11%), transient AST/ALT increases (5%), constipation (4%), rash (1%), flushing/warmth (< 1%), and dizziness (< 1%).

Answer 75

Ondansetron is a serotonin (5-hydroxytryptamine type 3, 5-HT3) receptor antagonist commonly used perioperatively as prophylaxis against and treatment of postoperative nausea and vomiting. One of the major locations for processing of emetogenic stimuli is the chemoreceptor trigger zone (CTZ) located near the base of the fourth ventricle. The CTZ includes a number of different receptor classes including 5-HT3, dopamine, and opioid. The GI mucosa also has numerous 5-HT3 receptors. Accordingly, 5-HT3 antagonists are very effective at treating and preventing (non-motion related) nausea and vomiting.

Answer 76

Uremia interferes with platelet activation and aggregation (primarily via effects on vWF and GPIIb-IIIa) and leads to increased production of platelet inhibitors (e.g. prostacyclin and nitric oxide).

Answer 77

PGE1 is a direct-acting vasodilator via prostanoid receptors on the vascular smooth muscle of the ductus arteriosus. It can dilate and improve flow through the ductus arteriosus or even reopen a mechanically closed ductus arteriosus. It is relatively selective for the ductus arteriosus, but may decrease both pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR). Hypotension is a side effect, especially in the setting of hypovolemia. Fever, flushing, bradycardia, gastric outlet obstruction, and CNS irritability are additional side effects.

Answer 78

In utero, the ductus arteriosus shunts blood from the pulmonary artery past the deflated lungs and directly into the descending aorta. At birth, lung expansion, increased alveolar oxygen tension, and several chemical mediators lead to a decrease in PVR. A combination of decreased PVR and increased SVR result in flow reversal in the ductus arteriosus. The flow reversal exposes the ductus arteriosus to oxygenated blood. A combination of exposure to oxygenated blood and decreasing prostaglandin E2 levels lead to mechanical closure of the ductus arteriosus within 1-2 days in full term neonates. True anatomic closure occurs over several weeks and requires fibrosis.

Answer 79

There are a variety of congenital heart diseases in neonates that require the patency of the ductus arteriosus. A neonate presenting with cyanosis and clinical suspicion of congenital heart disease within the first two weeks of life is likely to have a “ductal dependent lesion”. In this scenario, an empiric PGE1 infusion is often started as it is assumed progressive closure of the ductus arteriosus in the first few weeks of life is the inciting factor. For example, a neonate with a right-sided obstructive lesion preventing blood flow into the lungs, such as pulmonary atresia or critical pulmonary stenosis, is dependent on the ductus arteriosus to send blood from the aorta into the pulmonary vasculature for oxygenation. Closure of the ductus arteriosus would compromise ability to oxygenate the blood. An infusion of PGE1 will typically improve oxygenation in these neonates due to increased left to right shunting into the pulmonary vasculature. The infusion can be continued for maintenance of patency of the ductus arteriosus until surgical correction is possible.

Answer 80

Oxygen consumption in an adult is approximately 3-4 mL/kg/min and functional residual capacity (FRC) is 30 mL/kg.

Answer 81

Power = 1-β. Practically speaking, the power tells us the chance that the null hypothesis (e.g. no treatment effect from a particular drug) will be rejected when an alternative hypothesis is actually true (e.g. a drug does have a treatment effect). The larger the sample population (usually denoted as “n = some number”), the greater the power.

Answer 82

Amniotic fluid embolism is characterized by an early stage with pulmonary vasospasm and right heart dysfunction or failure leading to a second stage with pulmonary edema and left heart dysfunction or failure. Maternal coagulopathy (consumptive) occurs in the majority of cases. Emergency cesarean section is required if uterine hypertonus leads to fetal bradycardia and distress.

Answer 83

Obesity is characterized by a marked decrease in expiratory reserve volume, leading to a decrease in lung compliance and FRC. Decreased FRC also leads to airway closure and decreased PaO2.

Answer 84

Hepatopulmonary syndrome is defined as intrapulmonary vascular dilatations and increased alveolar-arterial (A-a) oxygen gradient, in the setting of end-stage liver disease. Hypoxia is improved when the patient lies flat (platypnea) and is worsened when the patient stands (orthodeoxia). The intrapulmonary vascular dilations cause increased perfusion relative to ventilation. Standing further worsens this ventilation-perfusion mismatch since gravity causes increased perfusion and pooling in the less-ventilated lower lung segmen

Answer 85

Nitroglycerin is a preferred agent for uterine relaxation. Other options include potent volatile anesthetics, inhaled amyl nitrite, and IV beta-adrenergic agonists. Indications for uterine relaxation include vaginal delivery of a twin in an abnormal position, breech presentations to deliver the fetal head, cesarean delivery of a fetus with an abnormality (such as hydrocephalus), inverted uterus, removal of retained placenta, and oxytocic overdose.

Answer 86

Mnemonics to help differentiate MELD from Child-Pugh: MELD: "I Crush Several Beers Daily" for INR, creatinine, sodium, bilirubin, dialysis Childs-Pugh: "Pour Another Beer At Eleven" for PT, Ascites, Bilirubin, Albumin, Encephalopathy

Answer 87

Respiratory alkalosis, such as from hyperventilation, can cause electrolyte abnormalities such as hypocalcemia, hypokalemia, and hypophosphatemia. Hypocalcemia is caused by increased calcium binding to negatively charged plasma proteins as the proteins release hydrogen ions to restore physiologic pH.

Answer 88

The SIADH is typically associated with the following electrolyte abnormalities: 1) Urine osmolality > 100 mOsm (often > 200-300 mOsm) 2) FENa > 1% 3) Urine Na+ >20 mEq/L 4) Low serum uric acid and BUN 5) Dilutional, euvolemic hyponatremia (serum Na+ < 135 mEq/L)

Answer 89

Serum albumin concentration decreases during pregnancy because of plasma expansion. Many other serum constituents such as fibrinogen, transferrin, and globulins increase, most likely due to the hormonal changes secondary to the pregnant state.

Answer 90

Increased chest wall stiffness, loss of muscle mass, flattening of the diaphragm, and increased compliance of lung parenchyma lead to several physiologic changes in elderly respiration. The volume at which small airways collapse increases with aging, such that by the mid-60s, closing capacity surpasses functional residual capacity and will eventually surpass tidal volume.

Answer 91

Gabapentin is an anticonvulsant effective in several neuropathic pain conditions including post-herpetic neuralgia and painful diabetic neuropathy. Gabapentin has efficacy at the α2-delta subunit of calcium channels.

Answer 92

Hyperthermia, hypernatremia, chronic ethanol abuse, and increased central neurotransmitter levels (e.g. MAOIs, amphetamine, cocaine, ephedrine, and levodopa use) increase MAC requirements for anesthetic agents.

Answer 93

The Bohr effect refers to the shift in the oxygen dissociation curve caused by changes in the concentration of carbon dioxide or the pH of the environment.

Answer 94

The Haldane effect described hemoglobin’s ability to carry increased amounts of CO2 in the deoxygenated state as opposed to the oxygenated state. This is due to the fact oxygenated hemoglobin reduces the amount of CO2 bound to hemoglobin in addition to the histidine amino acid of hemoglobin being an important hydrogen ion buffer at physiologic pH.

Answer 95

The most common primary tumor of the heart is a cardiac myxoma, which is typically located in the left atrium. However, metastatic disease to the heart is not uncommon from adjacent lung or renal cancer. Cardiac tumors have the potential to cause arrhythmias, ventricular obstruction, heart failure, pulmonary edema, pulmonary hypertension, arterial hypoxemia, dyspnea, positional hemodynamic compromise and embolism.

Answer 96

Pseudocholinesterase deficiency prolongs the actions of succinylcholine and mivacurium which can lead to prolonged neuromuscular blockade and apnea.

Answer 97

Echothiophate is an anticholinesterase used to treat refractory glaucoma by causing miosis. Since it inhibits BCHE, systemic absorption can cause up to a 95% decrease in BCHE function, thereby potentiating the effects of succinylcholine.

Answer 98

Cushing syndrome is characterized by a group of signs and symptoms resulting from prolonged exposure to excess cortisol. Classic symptoms include moon facies, buffalo hump, abdominal weight gain, thinning of the extremities, hirsutism, elevated blood sugar, and mood changes.

Answer 99

Parathyroid hormone (PTH) is released in response to decreasing serum calcium levels. PTH stimulates osteoclasts, increasing bone resorption and raising serum calcium. PTH also stimulates reabsorption of calcium from the distal renal tubule.

Answer 100

Fenoldopam is a selective dopamine-1 agonist that increases renal blood flow despite decreased systemic arterial blood pressure. Fenoldopam has little to no alpha, beta, or dopamine-2 receptor agonist activity.

Answer 101

Hypercarbia, acidosis, hyperthermia, and high 2,3-DPG levels, all shift the oxygen-hemoglobin dissociation curve to the right and increase oxygen unloading to tissues.

Answer 102

Metoclopramide is a dopamine antagonist centrally and a cholinergic agonist peripherally. It is used perioperatively as an antiemetic. By promoting gastric emptying and increasing gastroesophageal sphincter tone, it may decrease the risk of pulmonary aspiration. It is typically given in doses of 5-10 mg IV 15-30 minutes prior to induction to allow sufficient time for drug onset. However, drug combinations involving metoclopramide are not found to reduce PONV to a greater extent than monotherapy.

Answer 103

Metoclopramide inhibits plasma cholinesterase and can increase the duration of action of succinylcholine.

Answer 104

The cardiovascular effects of milrinone can be summarized as: increased inotropy, increased lusitropy, increased ejection fraction, increased stroke volume, increased cardiac output, decreased afterload, decreased preload, pulmonary vasodilation, and systemic vasodilation.

Answer 105

Milrinone is a phosphodiesterase III (PDE3) inhibitor which increases inotropy. Both milrinone and inamrinone (formerly known as amrinone) act by inhibiting the PDE3 isoenzyme which is responsible for the cleavage of intracellular cyclic adenosine monophosphate (cAMP). This allows for greater diastolic storing of calcium (which is facilitated by cAMP) by the sarcoplasmic reticulum which improves diastolic relaxation, a physiologic effect known as lusitropy. Lusitropy may be depicted on the myocardial pressure-volume loop as a rightward shift of the diastolic filling phase

Answer 106

The cricothyroid muscle is innervated by the external branch of the SLN. All other laryngeal muscles are innervated by the RLN. Bilateral RLN palsy or injury results in respiratory distress but unilateral injury or palsy typically does not.

Answer 107

The liver extensively metabolizes nicardipine and, as a result, hepatic insufficiency can result in prolonged half-life Nicardipine is a calcium-channel blocker; more specifically, it is an antagonist of calcium influx through the slow channels of cell membranes. It is an effective coronary and peripheral arterial dilator. Nicardipine can be used to relieve angina, especially those due to coronary artery spasms. It is also useful as an anti-hypertensive drug, particularly in neurosurgical patients. However, the advantage of nicardipine is that it does not decrease cardiac function.

Answer 108

Nicardipine decreases systemic vascular resistance, but also increases cardiac contractility (C). The exact mechanism of this positive inotropic effect is unknown.

Answer 109

Preservation of THBF amongst volatile anesthetics at 1 MAC, from greatest to least, is sevoflurane > isoflurane > halothane.

Answer 110

The duration of action of midazolam (half-life 1.7-2.6 hours) exceeds that of flumazenil (half-life 0.7-1.3 hours). This makes recrudescence of benzodiazepine-induced somnolence after metabolism of flumazenil likely in this context. Repeated dosing of flumazenil or flumazenil infusion may be necessary to prevent recrudescence after an initial bolus of flumazenil.

Answer 111

pulmonary edema

Answer 112

One-lung ventilation (OLV) creates a right to left pulmonary shunt, which has the greatest effect on the less soluble inhalational anesthetics, such as desflurane.

Answer 113

Inhalational anesthetics reach equilibrium when the anesthetic partial pressures of the alveolus, blood, and CNS become equal. The faster the alveolar fraction (FA) of inhaled agent approaches the fraction of inspired (FI) agent, the faster the agent will reach equilibrium. Insoluble agents (e.g. desflurane, nitrous oxide) have a low blood to gas partition coefficient. Therefore, their partial pressures quickly build in the alveoli. More soluble anesthetics (e.g. halothane, isoflurane) will diffuse across the alveoli and into the alveolar capillary bed more readily, thereby increasing the time needed reach this equilibrium.

Answer 114

Acoustic impedance is the product of the density of a medium and the propagation speed of sound through that medium. Ultrasound reflections that occur at the interface of different mediums are due to the changes in acoustic impedance. Since propagation speed changes slightly between biological mediums, acoustic impedance is primarily dependent upon density.

Answer 115

After an MI wait 14 days after balloon angioplasty, 30 days after BMS, 60 days if no coronary intervention, and 180 days after DES for elective noncardiac surgery.

Answer 116

Bottom Line: In the setting of non-ST elevation myocardial infarction and acute mitral regurgitation, there is high suspicion for papillary muscle rupture. The posteromedial papillary muscle receives a single blood supply from the right coronary artery in about two-thirds of patients. It is more susceptible to infarct than the anterolateral papillary muscle, which receives dual blood supply from the left anterior descending artery and left circumflex coronary artery.

Answer 117

The NMDA receptor is an inotropic glutamate receptor that functions as a nonspecific ion channel when activated. Activation only occurs when glutamate is bound to the receptor AND the cell is depolarized. The receptor’s effects are primarily mediated via increased intracellular calcium.

Answer 118

Administration of magnesium along with ketamine can potentiate the effects of ketamine.

Answer 119

Full flow CPB is maintained 20-30 minutes after reaching goal temperature to ensure adequate cerebral cooling prior to stopping circulation. Operative time is aimed at 45-60 minutes or less and is the only factor shown to improve outcomes.

Answer 120

The Poiseuille Law states that: Q = ΔP(π * radius4) / (8 * viscosity * length) Where: Q = flow, Δ = change in, P = pressure, π = 3.14159… (the mathematical constant). Notice the radius is taken to the fourth power in Poiseuille equation. Equivalent changes in the radius as compared to other parameters, will make the most impact on overall flow through the vessel. The radius of the vessel is directly proportional to flow and inversely proportional to resistance.

Answer 121

The musculocutaneous nerve travels within the belly of the coracobrachialis muscle. The nerve may therefore be neglected during an axillary brachial plexus block for distal upper extremity surgery since it is not contained within the axillary sheath. The median, ulnar, and radial nerves (as well as the axillary artery) are contained within the sheath.

Answer 122

Examples of cardiovascular medications that can be given IM include, but are not limited to: atropine, glycopyrrolate, ephedrine, epinephrine, phenylephrine, and hydralazine.

Answer 123

Epinephrine is a direct agonist at α1, α2, β1, and β2 adrenergic receptors. It increases contractility, heart rate, and cardiac output.

Answer 124

Ephedrine is an indirect-acting sympathomimetic. It stimulates α and β adrenergic receptors primarily by triggering release of norepinephrine.

Answer 125

Norepinephrine is a direct α1, α2, and β1 agonist. It significantly increases blood pressure but its effects on heart rate and cardiac output are dependent on systemic vascular resistance. Adrenergic stimulation is α >> β leading to potent vasoconstriction.

Answer 126

Phenylephrine is a direct-acting α1 agonist. It improves blood pressure via increased preload and afterload but typically causes a reflexive bradycardia. Although phenylephrine mimics many of the effects of norepinephrine, it is less potent and causes venoconstriction > arterial constriction

Answer 127

Inhalational induction is delayed in the setting of a right-to-left intracardiac shunt. faster with IV induction

Answer 128

Angiotensin I (AI) is cleaved and converted to Angiotensin II (AII) in the pulmonary circulation by angiotensin converting enzyme (ACE).

Answer 129

Hyperventilation leads to decreased CBF by decreasing PaCO2. CBF changes 1-2 mL/100 g/min per every 1 mmHg change in PaCO2.

Answer 130

Pulmonary shunt is increased by increased oxygen concentrations, which leads to blunting of hypoxic pulmonary vasoconstriction and microatelectasis.

Answer 131

Additionally, high concentrations of oxygen decrease functional residual capacity through development of microatelectasis. This occurs because of alveolar collapse – when higher concentrations of oxygen are used, less nitrogen is part of the alveolar gas. Nitrogen helps keep alveoli ‘stented’ open, helping to decrease the amount of micro collapse. Less nitrogen results in more alveolar collapse and what is called microatelectasis. Some of this effect can be blunted by using certain maneuvers such as positive end expiratory pressure or recruitment maneuvers. It should be mentioned that the verdict on oxygen concentration in the intraoperative period is still debated and further studies are needed to really determine the optimal concentration.

Answer 132

Several second-line therapies exist to help control postpartum hemorrhage due to uterine atony. Being aware of these contraindications - methylergonovine in coronary artery disease and preeclampsia/eclampsia, and carboprost in asthma - is essential to providing appropriate anesthetic care.

Answer 133

NSAIDs lead to a decrease in the production of prostaglandins. Prostaglandin E2 is the key mediator of both peripheral and central pain sensitization. Peripherally, prostaglandins do not directly mediate pain; rather, they contribute to hyperalgesia by sensitizing nociceptors to other mediators of pain sensation such as histamine and bradykinin. Centrally, prostaglandins enhance pain transmission at the level of the dorsal horn by increasing the release of substance P and glutamate from first-order pain neurons, increasing the sensitivity of second-order pain neurons, and inhibiting the release of neurotransmitters from the descending pain-modulating pathways.

Answer 134

Dexmedetomidine undergoes extensive hepatic metabolism including conjugation, n-methylation, and hydroxylation followed by conjugation before being excreted in urine and feces. Its elimination half-life is 2-3 hours.

Answer 135

Dexmedetomidine is a selective α2-adrenergic agonist (α2:α1 = 1600:1) that causes inhibition of presynaptic norepinephrine release from peripheral and central nervous system neurons (particularly those in the spinal cord and locus ceruleus in the brainstem). This results in analgesia, anxiolysis, sedation, and sympatholysis.

Answer 136

During immersion extracorporeal shock wave lithotripsy (ESWL), a mechanically generated shock wave is passed through water toward the area of calculus. When the wave encounters a different density (such as the renal calculus), energy is released, which will break up the stone. If the shock travels through the heart, it may disrupt normal conduction, and cause dysrhythmias, and in the worst case scenario, the shock will reach the heart during repolarization (the T wave on the ECG), and cause ventricular fibrillation. For this reason, the shocks are timed to the R wave on the ECG (the refractory period of the cardiac cycle).

Answer 137

Hypoxemia primarily occurs during OLV due to perfusion of the non-dependent (non-ventilated) lung, even in the setting of appropriate hypoxic pulmonary vasoconstriction. This leads to a right-to-left intrapulmonary shunt and mixing of deoxygenated blood into the systemic circulation. Except in the case of severe, acute hypoxemia, the first steps for management of hypoxemia during OLV are to confirm proper positioning of the double-lumen endotracheal tube and ensure 100% oxygen is being delivered.

Answer 138

Non-ventilated lung

Answer 139

the ventilated lung; the one that is generally lower to gravity

Answer 140

: Potentiation of neuromuscular blockade is seen with volatile anesthetics, local anesthetics, aminoglycosides, lithium, calcium channel blockers, acute phenytoin, and magnesium.

Answer 141

Metoclopramide has inhibitory effects upon plasma cholinesterase, therefore it may prolong the duration of mivacurium and succinylcholine by means of reduced degradation.

Answer 142

Succinylcholine is a commonly used muscle relaxant. One of the most commonly reported side effects of succinylcholine administration is muscle pain or myalgia. Myalgia occurs in roughly 50% of patients who receive succinylcholine alone. Pain is often considered inconvenient and lasts 1-2 days. Pain is more likely in females of child-bearing age. Additionally, patients who are in better physical condition are less likely to experience myalgia.

Answer 143

Phase 1 block is the normal response to succinylcholine where the train-of-four (TOF) ratio stays >70% (subjectively, all four twitches feel equal) and is associated with fasciculations (though an absence of post tetanic fasciculations), a decreased response to single twitch stimuli, absence of fade to tetanus, enhancement of neuromuscular blockade (NMB) by anticholinesterases, and rapid recovery.

Answer 144

Dibucaine is a local anesthetic that was found to inhibit normal pseudocholinesterase activity by 80%, meaning a normal patient has a dibucaine number of 80. This number is proportional to the amount of normal pseudocholinesterase. A dibucaine number of 20 indicates a homozygous patient, a dibucaine number of 40-70 indicates a heterozygous patient.

Answer 145

Both phase 1 and phase 2 blockades of succinylcholine administration display decreased contraction with single twitch stimulus. Phase 1 blockade is associated with fasciculations, minimal fade to TOF (TOF ratio >70%), and enhancement of neuromuscular blockade (NMB) by anticholinesterases. Phase 2 blockade is associated with repeated doses or an infusion of succinylcholine, resembles NDNMB, and can be partially reversed with anticholinesterases. The degree of pseudocholinesterase deficiency is established by the dibucaine number, which is proportional to the amount of normal pseudocholinesterase.

Answer 146

Cerebral vasospasm is most likely to develop between days 2-10 or 3-15 (depending on source) after a subarachnoid hemorrhage (SAH) and the exact reasons why this interval is the peak time period is not well understood.

Answer 147

Transcranial Doppler (TCD) may also be performed every 24-48 hours to screen for cerebral vasospasm. This study assesses the flow velocity (FV) of the middle cerebral artery (MCA) and the internal carotid artery (ICA) and compares FVMCA to FVICA. Generally, vasospasm is considered if the FVMCA >120 cm/s or the FVMCA:FVICA ratio is larger than 3. The most efficacious form of treatment and prevention of cerebral vasospasm was thought to be the use of hypervolemia, hypertension, and hemodilution (“Triple H” therapy). However, no human studies have ever shown improved outcomes and there are detriments to this treatment including edema, anemia, and possibly worsening outcomes. Newer treatments focus on euvolemia and management of blood pressure with vasopressor support if needed to maintain CPP.

Answer 148

Transcranial Doppler is used during the perioperative period for CEA procedures to measure blood flow velocities, detect embolization to the brain, identify shunt function or malfunction, and detect asymptomatic carotid artery occlusion and/or hyperperfusion syndrome. The technique involves assessment of the middle cerebral artery.

Answer 149

The anterior wall is supplied by the left anterior descending artery

Answer 150

Right coronary supplies portions of the interventricular septum and the inferior wall.

Answer 151

the inferior wall

Answer 152

Circumflex artery

Answer 153

SLUDGE •Acetylcholine is the neurohumoral mediator at the cholinergic junctions. Since acetylcholinesterase is the enzyme that degrades acetylcholine following stimulation of a nerve, by inhibiting acetylcholinesterase, organophosphates allows acetylcholine to accumulate and result in initial excessive stimulation followed by depression.

Answer 154

Norepinephrine restores perfusion pressure, improves organ function, and corrects splanchnic ischemia in hypotensive patients and is thus the first-line vasopressor in patients with septic shock. This is assuming adequate fluid resuscitation has already occurred. Norepinephrine increases systemic arterial pressure with variable effects on cardiac output and heart rate through both α- and β-adrenergic receptor agonism. Increased systemic vascular resistance improves end-organ perfusion, accompanied by a decrease in lactate levels. In volume-resuscitated, hypotensive patients in septic shock, norepinephrine improves renal function. Norepinephrine can decrease organ perfusion in under-resuscitated patients, especially when high-dose infusions are used.

Answer 155

GA Prophylactic cervical cerclage is usually performed under neuraxial anesthesia. When cervical dilation and bulging membranes are present, general anesthesia may be preferable if acceptable to the patient. In the absence of studies showing fetal outcomes, no technique is contraindicated, however, general anesthesia has the advantage of causing uterine relaxation which facilitates replacement of membranes.

Answer 156

Briefly, it is performed by 1) placing a small IV in the operative extremity, 2) placing a double tourniquet proximally on the extremity, 3) exsanguinating the extremity with an Esmarch bandage, 4) inflating the proximal tourniquet cuff, and 5) injecting local anesthetic (commonly 40-50 ml 0.5% lidocaine, though some recommend smaller volumes of a higher concentration). If the patient experiences tourniquet pain, the distal cuff is inflated then the proximal cuff is deflated. Following the procedure (or after 20-30 minutes after the local anesthetic was injected if the procedure is short), the tourniquet is then released. Although a dorsal hand vein is most commonly used, the site of IV placement and injection does not affect the block efficacy (D)1.

Answer 157

The mechanism of action of an upper extremity Bier block is believed to be diffusion of the local anesthetic from the veins into the capillaries surrounding peripheral nerves and then into the vasa nervora, which will then produce the nerve conduction block. Local anesthetic also diffuses extravascularly into the small nerves supplying the skin

Answer 158

Supraventricular tachycardia in patients with WPW can be safely managed with procainamide.

Answer 159

In a patient with asthma, nonspecific (beta1 and beta2) beta-blockade can exacerbate bronchospasm thus it should only be given after all other causes of sinus tachycardia have been ruled out.

Answer 160

Epidural anesthesia has been used safely in patients with MS and is not associated with exacerbations or worsening symptoms of MS. However, spinal anesthetics are often avoided because of risk of demyelinated nerves being sensitive to local anesthetics, which may cause a local toxicity to the nerve. Spinal anesthesia can be performed safely, though it is controversial. There is little evidence to either support or refute the use of subarachnoid block in patients with MS.

Answer 161

Succinylcholine is not associated with exacerbations of MS. Although, succinylcholine is associated with hyperkalemia and should be avoided in patients with MS. Succinylcholine induced hyperkalemia results from denervated muscle with upregulated immature acetylcholine receptors.

Answer 162

DAMAGE TO SLN (INNERVATES CRICOTHYROUD MUSCLE)

Answer 163

Antiphospholipid syndrome is a prothrombotic disorder resulting in both venous and arterial thrombosis. It is characterized by the presence of two autoantibodies, lupus anticoagulant and anticardiolipin antibody. Lupus anticoagulant has no true anticoagulant activity; instead, the anticoagulant activity is a laboratory artifact that affects the phospholipid-dependent coagulation assays. In the absence of an underlying coagulation deficit or anticoagulant therapy, the prolonged aPTT does not suggest a bleeding tendency and neuraxial anesthesia may be administered in this setting.

Answer 164

1st: Norepiniephrine 2nd: Vaso OR EPI The Surviving Sepsis Campaign guidelines have changed several times. All versions have included norepinephrine as the first-line agent. The first iteration recommended vasopressin as the second-line drug of choice. The second iteration lowered the dose of vasopressin and also suggested epinephrine as the second-line drug of choice instead of vasopressin. The Sepsis-3 guidelines then changed to either vasopressin or epinephrine as the second-line agent.

Answer 165

Increases CO and SVR NO--increased mortality Dopamine raises mean arterial pressure by increasing cardiac output and, to a lesser extent, systemic vascular resistance. Dopamine effectively improves urine output by either improving overall hemodynamics, exerting a direct diuretic effect, or by decreasing the release of antidiuretic hormone via baroreceptor responses. The α-agonistic dosage of dopamine varies but may empirically begin at 10 mcg/kg/min and be titrated to effect. However, studies have shown an increased rate of morbidity including cardiac arrhythmias when dopamine is used in sepsis.

Answer 166

Norepinephrine is the first-line vasopressor for treatment of septic shock after adequate intravascular volume expansion. Steroids may be helpful in resistant hypotension, but do not have any mortality benefits. Early administration of empiric antibiotics is recommended. The use of low-dose dopamine for renal protection confers no mortality benefit.

Answer 167

Down syndrome patients frequently have cardiovascular defects. The most common of these is endocardial cushion defects. Down syndrome is associated with atlantoaxial instability, hypotonia, and gastrointestinal, genitourinary, respiratory, vascular, and metabolic defects.

Answer 168

Diabetes insipidus (DI) is characterized by a deficiency of antidiuretic hormone and can be caused by pituitary disease, trauma, infiltrative disease, brain tumors, and neurosurgical procedures. A patient with diabetes insipidus would likely present with polyuria, hypernatremia, a high plasma osmolality, and a low urine osmolality. Management includes administration of DDAVP and isotonic intravenous fluids to maintain euvolemia.

Answer 169

The syndrome of inappropriate release of antidiuretic hormone (SIADH) is characterized by water retention and hyponatremia due to overactive ADH. Oliguria would likely be seen

Answer 170

Treatment for MS includes beta-interferon treatment, monoclonal antibody treatment (e.g. natalizumab), or immunosuppression. Steroids are not commonly used for chronic treatment but may be used to shorten an exacerbation.

Answer 171

Guillain-Barré syndrome (GBS) is associated with SIADH, which causes hyponatremia. SIADH develops when ADH is released inappropriately. SIADH was detected in nearly 50% of patients who developed GBS. The severity of hyponatremia was associated with the severity of GBS. GBS is an autoimmune demyelinating polyneuropathy that often develops following gastrointestinal or respiratory illnesses. GBS has also been weakly linked to vaccinations. GBS often begins with sensory changes (paresthesias) which lead to progressively ascending weakness. Many patients experience autonomic dysfunction which can become quite severe manifesting as hypotension, hypertension, cardiac dysrhythmias, and ileus. Dysrhythmias can be severe such that arterial catheterization may be necessary.

Answer 172

Laparoscopic surgery is typically achieved through intraperitoneal insufflation with carbon dioxide (CO2). Intraperitoneal insufflation produces significant hemodynamic changes secondary to increased abdominal pressure ("pneumoperitoneum"), including a decrease in right heart filling pressures, decreased renal and splanchnic blood flow, and arrhythmias. CO2 is absorbed into the vasculature, producing hypercarbia and a resultant vasodilation. CO2 absorption produces an overall sympathetic response. In addition, the renin-angiotensin system is activated with resultant vasopressin release. Increased SVR and MAP is primarily the result of increased vasopressin levels and, to some degree, a CO2-induced sympathetic response plus a compressed intra-abdominal arterial tree.

Answer 173

A serum creatinine concentration greater than 0.8 mg/dL or a blood urea nitrogen concentration greater than 13 mg/dL (which are normal values for the nonpregnant patient) suggests renal insufficiency in the pregnant woman.

Answer 174

Vasogenic edema is caused by disruption of the blood brain barrier resulting in cerebrovascular permeability and leakage of serum proteins into the brain parenchyma. It is the escape of fluids and proteins from the vascular system into the parenchyma.

Answer 175

Cytotoxic brain edema occurs following ischemic conditions; the blood brain barrier remains intact however disturbance of osmoregulatory functions of the brain occurs. In other terms, cell membranes become more permeable most often due to disruption of ion channels following cellular injury.

Answer 176

Primary hyperthyroidism is characterized by elevated T3, T4 (free and total), and thyroid hormone binding ratio, and a low or normal TSH.

Answer 177

Anticholinergic symptoms include: tachycardia, altered level of consciousness, hyperthermia (“atropine fever”), flushing, dry mouth, mydriasis, constipation, and urinary retention. Recall: “dry as a bone, mad as a hatter, blind as a bat, and hot as a hare.”

Answer 178

Hydroxyethyl starches are synthetic colloids useful for volume resuscitation due to prolonged intravascular half-lives. Hetastarches are traditionally associated with a higher risk of coagulopathies (platelet adhesion interference, reduced factor VIII:C and vWF levels, and PTT prolongation) than the newer, lower molecular weight tetrastarches.

Answer 179

discogenic pain is often described as decreased with standing and increased with bending/sitting. With acute disc herniation there is often a positive straight leg test and there may be associated weakness.

Answer 180

Chronic hypercalcemia from hyperparathyroidism leads to the constellation of symptoms of nephrolithiasis, abdominal discomfort, osteopenia, bone pain, and psychological depression.

Answer 181

Carcinoid syndrome is a constellation of symptoms that occurs from the release of serotonin from metastatic carcinoid tumors into the systemic circulation. Carcinoid tumors are usually slow-growing, benign, tumors that arise from neuroendocrine cells, usually in the small intestine, and evolve to secrete an excess amount of the neurotransmitter 5-hydroxytryptamine (5-HT), better known as serotonin. The GI tract is the most common site of origin for these tumors. Carcinoid tumors are usually asymptomatic; patients may have vague symptoms of abdominal pain, intestinal obstruction, diarrhea, and GI bleeding. Once carcinoid tumors have metastasized, either into the hepatic or pulmonary circulation, they release vasoactive peptides into the systemic circulation, which causes patients to have signs and or symptoms of carcinoid syndrome. Symptoms of carcinoid syndrome include cutaneous flushing, vomiting, diarrhea, hypotension or hypertension, abdominal pain, dizziness, palpitations, and bronchoconstriction.

Answer 182

When performing an axillary brachial plexus block, three of the four major nerve branches to the arm are contained within the axillary sheath and surround the axillary artery. The radial nerve is the most posterior and is closest to the humerus and is commonly described as being in the six o’clock position relative to the artery when viewed on ultrasound. The median nerve is anterolateral to the artery and is often found in the nine or ten o’clock position. The ulnar nerve is anteromedial to the artery and typically located in the three o’clock position.

Answer 183

ACT is a functional assessment of the intrinsic and final common pathway of the coagulation system. Whole blood is added to a tube that contains an activator substance (celite or kaoline) and time to clot formation is measured. The normal ACT is around 107 seconds. The ACT is commonly used in cardiac surgery to evaluate the anticoagulant effect of heparin. A value between 400-480 seconds is typically required to initiate cardiopulmonary bypass.

Answer 184

Neonates are more sensitive to morphine due to opioid receptor immaturity and inability to metabolize morphine into its metabolites. CYP2D6, UGT2B7, and CYP3A4 are all decreased at birth, and these enzymes allow codeine activation, morphine inactivation, and fentanyl inactivation, respectively.

Answer 185

The renin-angiotensin-aldosterone system (RAAS) is one of the primary regulators of volume and blood pressure. Angiotensinogen circulates in the plasma until cleaved by renin to form angiotensin I. Renin is released by the juxtaglomerular apparatus in response to β1 activation, decreased renal perfusion pressure (glomerulus), or decreased NaCl concentration at the macula densa (distal convoluted tubule). Angiotensin I is cleaved to form the active angiotensin II by angiotensin-converting enzyme (ACE) in the lungs.

Answer 186

Brain natriuretic peptide (BNP) is released from the heart in response to myocardial stretch receptors in the right and left ventricles similarly to atrial natriuretic peptide (ANP) released from the atria. Both ANP and BNP cause vasodilation, natriuresis/diuresis, and inhibition of the renin-angiotensin-aldosterone system in response to volume overload states (CHF, cirrhosis, renal failure, right heart failure). BNP causes inhibition of the sodium-potassium ATPase in the collecting ducts to promote sodium excretion.

Answer 187

Platelets are synthesized and released by megakaryocytes, which are produced in the bone marrow. Of note, thrombopoietin (TPO) is produced by the liver and stimulates bone marrow release of megakaryocytes. Thrombocytopenia is a common finding in cirrhosis given a deficiency of TPO and hypersplenism.

Answer 188

VWF is synthesized from the Weibel-Palade bodies and subendothelium. Desmopressin (or DDAVP) is sometimes used to facilitate the release of vWF in coagulopathic patients or in patients with von Willebrand disease via activation of the V2 receptor.

Answer 189

The critical temperature of a given gas is the temperature above which it is not possible to convert said substance into liquid form by pressure alone. For nitrous oxide, this temperature is 36.5 degrees Celsius. Below this temperature, nitrous oxide can be liquefied when stored under pressure, as in the case of an E-cylinder being utilized in a typical operating room environment.

Answer 190

Plasma and red blood cell esterases = clevidipine, esmolol, remifentanil

Answer 191

Pseudocholinesterase = succinylcholine, mivacurium, ester local anesthetics

Answer 192

Clevidipine is an intravenous, ultra-short acting, dihydropyridine calcium channel antagonist with selectivity for arteriolar vasodilation that is rapidly metabolized by plasma and red cell esterases providing its short duration of action. The other calcium channel blockers are metabolized by the cytochrome P450 system in the liver.

Answer 193

The mechanism of beta-agonist induced bronchodilation is via Gs effects, cAMP generation, decreased intracellular calcium, and resulting airway muscle relaxation.

Answer 194

Both CN IX and CN X carry signals generated in response to arterial hypoxia from the carotid and aortic bodies. The primary target for signals generated by carotid bodies is the chemosensitive area of the medulla, and an increase in signal generates an increase in minute ventilation. Aortic body activation results in a parasympathetic response throughout the body due to stimulation of the vagus nerve. Opioids, benzodiazepines, and inhaled anesthetics all attenuate the hypoxic ventilatory drive as a result of decreased signal production in the carotid bodies.

Answer 195

Carotid body denervation following carotid endarterectomy can occur. Loss of a unilateral carotid body function may result in a decreased response to mild hypoxemia, with a lower threshold (PaO2 about 50 mmHg) generating an equivalent ventilatory response. Bilateral loss of carotid body function following bilateral carotid endarterectomy results in a complete loss of normal ventilatory response to acute hypoxia, and the patient becomes dependant on the hypercarbic respiratory drive. These patients have a baseline elevated PaCO2, and profound respiratory depression may result from administration of either opioids or benzodiazepines.

Answer 196

Muscarinic effects of cholinergic drugs include bradycardia, bronchospasm, miosis, salivation, lacrimation, defecation, urination, and sweating

Answer 197

Nicotinic effects of cholinergic drugs include muscle fasciculations, weakness, paralysis, and tachycardia.

Answer 198

Drugs that act on the parasympathetic nervous system are called cholinergic or cholinomimetic because their effects mimic acetylcholine. They do so either directly as agonists or indirectly by inhibiting acetylcholinesterase

Answer 199

Mnemonic devices for muscarinic effects: SLUDGE-Mi "Sludge Me": Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis, Miosis DUMBELS: Defecation/Diaphoresis, Urination, Miosis, Bradycardia/Bronchospasm, Emesis, Lacrimation, Salivation

Answer 200

The rate of inhaled anesthetic induction (FA/FI) is increased with increased minute ventilation. This effect is greatest with the agents with high solubility, including halothane and isoflurane.

Answer 201

Acetylcholine (ACh) is the primary neurotransmitter released by the preganglionic neurons of the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). ACh is released from vesicles near the presynaptic membrane to activate nicotinic acetylcholine receptors (nAChR) in the synapse.

Answer 202

Sympathetic outflow occurs from T1 to L2. The sympathetic nervous system is composed of a two-neuron system including: 1) Preganglionic: short, myelinated, release acetylcholine (nicotinic receptors), runs to paravertebral ganglia, prevertebral ganglia, and the adrenal medulla 2) Postganglionic: long, unmyelinated, release norepinephrine (most locations), ATP (vascular smooth muscle), or acetylcholine (eccrine sweat glands via muscarinic receptors)

Answer 203

American Heart Association guidelines recommend beginning perimortem cesarean (resuscitative hysterotomy) at four minutes and completing delivery of the fetus by five minutes following cardiac arrest. Manual left uterine displacement should be performed during resuscitation, including during the performance of perimortem cesarean until the fetus is delivered.

Answer 204

the patient should be placed supine for chest compressions (Class I; Level of Evidence C) and continuous manual left uterine displacement (pushing uterus to the left) should be performed. This specific guideline change occurred in 2015.

Answer 205

Physostigmine is an acetylcholinesterase inhibitor that can cross the BBB and counteract the sedative effects of scopolamine.

Answer 206

``` parts of the scotty dog Transverse process: nose Pedicle: eye Pars interarticularis: neck Superior articular facet: ear Inferior articular facet: front leg ```

Answer 207

Andexanet alfa is a recombinant derivative of factor Xa, and acts as a "decoy receptor", effectively binding factor Xa inhibitors (such as rivaroxaban, apixaban, and edoxaban) with higher affinity than factor Xa itself. Its approval represents an important step forward in anticoagulation management, as direct factor Xa inhibitors (like rivaroxaban and apixaban) continue to grow in popularity. Direct factor Xa inhibitors have oral bioavailability, do not require laboratory monitoring or have special dietary requirements (unlike warfarin), and have relatively attractive side effect profiles.

Answer 208

Apixaban is an oral direct factor Xa inhibitor, like rivaroxaban. While some anticoagulation agents, such as dabigatran, can at least be partially removed with the help of hemodialysis, apixaban (and, in fact, rivaroxaban) are notable in that they are NOT dialyzable.

Answer 209

Bivalirudin is a direct thrombin inhibitor with a relatively short half-life (25 minutes in patients with normal renal function; up to three hours in dialysis-dependent individuals). Its primary application is in patients undergoing percutaneous coronary intervention (PCI). As of 2018, there is no known antidote. Given its short half-life, treatment of hemorrhage is primarily supportive. Idarucizumab is a monoclonal antibody fragment that binds to the active site of dabigatran, a direct thrombin inhibitor with oral bioavailability. It is used for the management of serious bleeding caused by dabigatran but does not appear to be effective against bleeding caused by other direct thrombin inhibitors (such as bivalirudin or argatroban).

Answer 210

The respiratory centers in the brain are located in the cerebral medulla, including both dorsal (inspiration) and ventral (expiration) respiratory groups. Mnemonic: "DIVE" for dorsal = inspiration, ventral = expiration.

Answer 211

respiratory acidosis Carbon dioxide readily crosses the blood-brain barrier, while hydrogen ions do not. Thus respiratory acid-base derangements have a much greater effect on cerebrospinal fluid pH and therefore cerebral blood flow than do metabolic acid-base derangements. These effects are short-lived, however, as bicarbonate levels will normalize cerebrospinal pH in the setting of sustained respiratory acidosis or alkalosis over the course of 6 to 8 hours.

Answer 212

In children with pyloric stenosis, serum alkalosis leads to CSF alkalosis. Even with correction of serum alkalosis (pH and bicarbonate), the CSF acid-base imbalance can persist. This CSF alkalosis can lead to postoperative apnea via the central control of ventilation.

Answer 213

The high-pressure section includes auxiliary E cylinders, which are drawn from when there is pipeline failure. Intermediate-pressure includes the hospital pipeline supply and portions of the anesthesia machine with pressures reduced by secondary pressure regulators in the 15-30 psig range. The low-pressure section begins at the flow control valves and includes the flowmeters, vaporizers, and fresh gas supply line.

Answer 214

The combination of MAOIs with meperidine can precipitate serotonin syndrome.

Answer 215

Signs of serotonin syndrome include clonus, hyperreflexia, tachycardia, hyperpyrexia, diaphoresis, ataxia, and confusion. The most accurate diagnostic criteria currently are the Hunter Toxicity Criteria Decision Rules. Criteria are met when the patient has one of the following: - Spontaneous clonus - Inducible clonus plus agitation or diaphoresis - Ocular clonus plus agitation or diaphoresis - Tremor plus hyperreflexia - Hypertonia plus temperature > 38 °C plus ocular clonus or inducible clonus Note that diaphoresis is more common with serotonin syndrome. In contrast, xeroderma (dry skin) is more common with central anticholinergic syndrome (CAS).

Answer 216

Neuroleptic malignant syndrome occurs in patients taking antipsychotic medication. It is characterized by muscle rigidity and altered consciousness. Both first-generation neuroleptic medications, such as haloperidol, and newer atypical antipsychotics have been implicated in neuroleptic malignant syndrome.

Answer 217

Carotid sinus ....Surgical stimulation cannot always be stopped in the event that bradycardia and hypotension occur during carotid procedures. Consider the minimally invasive transcarotid artery revascularization (TCAR) procedure. During this procedure, a balloon is inflated within the carotid artery and blood flow is reversed to reduce the risk of stroke during carotid stenting. If bradycardia occurs, deflating the balloon to stop the stimulus would significantly increase the risk of stroke. Additionally, flow reversal is dependent on blood pressure and therefore hypotension that occurs during this process can also increase the risk of stroke. Thus, prophylactic glycopyrrolate is commonly given before balloon inflation. Atropine is another option, but it typically avoided as it crosses the blood-brain barrier and can affect post-procedure neurologic examination

Answer 218

loss of a wave The central venous pressure tracing contains three systolic components (c wave, v wave, x descent) and two diastolic components (a wave, y descent). In patients with atrial fibrillation, two characteristic findings are the loss of the a wave and a prominent c wave.

Answer 219

The Boyle law says changes in gas volume is inversely related to the pressure on the gas. As the pressure increases, then the volume will decrease. If the pressure doubles, then the volume will decrease by half.

Answer 220

The Charles law explains the relationship between volume (V) and temperature (T), where V1 / T1 = V2 / T2.

Answer 221

relates pressure (P) with temperature (T), where P1 / T1 = P2 / T2.

Answer 222

The corneal reflex involves the ophthalmic branch of the trigeminal nerve (afferent limb) and the temporal and zygomatic branches of the facial nerve.

Answer 223

T3 is more potent than T4 due to its higher serum concentration on account of its decreased protein binding. Most circulating T3 is formed peripherally by the conversion of T4 by partial deiodination via the enzyme 5'-deiodinase.

Answer 224

Thyroid hormone production is regulated by thyroid-stimulating hormone (TSH), which is secreted by the anterior pituitary. TSH secretion is regulated by the hypothalamus and its secretion of thyrotropin-releasing hormone (TRH). These hormones feed back to control the serum level of T3 and T4.

Answer 225

Oxytocin and vasopressin (secreted, but not produced from the PP)

Answer 226

The process of peripheral T4-to-T3 conversion is targeted in treating hyperthyroidism with the drug propylthiouracil (PTU). In addition to central thyroid inhibition by inhibiting thyroperoxidase, PTU decreases peripheral conversion by inhibiting 5'-deiodinase.

Answer 227

increases the amplitude...like ketamine

Answer 228

Bethanechol, carbachol, and pilocarpine are examples of direct muscarinic acetylcholine agonists. These drugs are resistant to breakdown by acetylcholinesterase.

Answer 229

Desflurane should be avoided in children with preexisting pulmonary disease as it increases airway resistance and can lead to bronchospasm. Treatment of bronchospasm includes positive airway pressure, increasing FiO2, inhaled bronchodilators, and intravenous epinephrine for resistant bronchospasm.

Answer 230

Endogenous adrenergic agonists (epinephrine, norepinephrine, dopamine) cannot cross the blood-brain barrier. However, alpha-2 agonists like dexmedetomidine and clonidine can cross and bind to central receptors.

Answer 231

Radiation describes heat loss via photons, given off to the surrounding atmosphere. This type of heat transfer accounts for up to 60% of heat lost in the operating room setting, representing the most significant source of heat loss; convection is 15% Conduction is 10% Evalopration is 5%--though higher in kids

Answer 232

The reticular activating system is a collection of brain pathways that affect consciousness and wakefulness. The thalamus is responsible for transmission of signals from the reticular activating system to the cerebral cortex. Almost all anesthetics directly depress the RAS, thereby altering consciousness. Conversely, ketamine affects the thalamus, preventing fluid transmission of signals to the limbic cortex and producing its distinct dissociative effects, while also causing hyperexcitability and functional disorganization within the RAS.

Answer 233

The antifibrinolytic agents TXA and aminocaproic acid are both lysine analogs which bind to activated plasmin in the place of fibrin, and in doing so prevent fibrin breakdown. TXA has been utilized effectively for the control of hemorrhage following the administration of tPA for both ischemic stroke and pulmonary embolism due to this mechanism of action.

Answer 234

Protamine is a large, positively charged molecule that is given as an antidote to heparin. It chelates the large, negatively charged heparin molecule and prevents its binding with antithrombin 3 and its subsequent anticoagulant effect

Answer 235

Normal values for thromboelastography can be remembered by the rule of 6's: - R time around 6 minutes - Alpha angle around 60 degrees - Maximal amplitude around 60 mm - LY30 of around 6% These are rough estimates but are helpful as an approximation of normal values when interpreting TEG results.

Answer 236

: Brainstem auditory evoked potentials, also known as brainstem auditory evoked responses (BAERs), are the most resistant to the effects of volatile anesthetics.

Answer 237

Brainstem potentials are Barely affected, Sensory potentials are Somewhat affected, Motor potentials are Mostly affected, and Visual potentials are Very affected.

Answer 238

The adrenal cortex secretes different steroids from three distinct layers; each secretes a unique substance. The outer layer, zona glomerulosa, produces mineralocorticoids (aldosterone). The middle layer, zona fasiculata, produces glucocorticoids (cortisol). The innermost layer, zona reticularis, produces gonadocorticoids. Throughout the adrenal cortex, the cells contain lipid droplets made of cholesterol that form the basis of the steroids. The adrenal medulla is comprised of chromaffin cells that synthesize and secretes catecholamines. The predominant catecholamine is adrenaline, accounting for approximately 80%. Noradrenaline is also produced and secreted from the medulla, accounting for approximately 20%.

Answer 239

The mineralocorticoid aldosterone acts to retain sodium and water in response to stimulation of the renin-angiotensin system. The primary site of action is the distal convoluted tubules and collecting ducts of the kidney. Aldosterone acts on numerous other epithelial tissues and the intestine. In all these places, it acts to promote excretion of potassium in exchange for sodium. Water follows the sodium.

Answer 240

Cortisol is the body’s primary glucocorticoid. It is released from the zona fasciculata of the adrenal cortex, principally following ACTH secretion from the anterior pituitary. Cortisol levels typically follow a diurnal pattern, related to sleep patterns, with a peak in the early morning around wakening and a dip at midnight. Cortisol levels can be raised in response to several stimuli such as trauma, sepsis, heavy exercise, hypoglycemia, and acute anxiety. Glucocorticoids act to maintain blood glucose levels by promoting gluconeogenesis and fat metabolism.

Answer 241

Renin is secreted from the juxtaglomerular apparatus in response to a decrease in renal perfusion pressure. Angiotensinogen is a protein secreted from the liver into the blood. It is converted by renin to angiotensin I. In the lungs angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II acts on the zona glomerulosa of the adrenal cortex to release the mineralocorticoid, aldosterone. Angiotensin II also acts on other systems – in the blood vessels it stimulates smooth muscle contraction, in the brain, it activates thirst centers, and in the posterior pituitary it stimulates the release of antidiuretic hormone. Angiotensin II and aldosterone both act to maintain fluid balance and blood pressure. Conn syndrome is mineralocorticoid excess. It results in potassium depletion, sodium retention, polyuria, tetany, and weakness. In adrenal medulla tumors (pheochromocytoma), the ratio of catecholamines produced is reversed with 80% of noradrenaline and 20% of adrenaline.

Answer 242

greater than 0; open means 0 . "0pen"

Answer 243

morphine metabolized via CYP2D6 (six letters + one D in codiene) poor metabolizers get little effect from drug fast metabolizers easily overdose

Answer 244

The sites at which core temperature can be measured are the pulmonary artery, distal aspect of the esophagus, tympanic membrane, and nasopharynx.

Answer 245

The pulse pressure increases as the cuff is moved more distally. Pulse pressure is equal to the systolic minus the diastolic pressure (PP = SBP - DBP). Hence, the SBP increases and DBP decreases more distally. In fact, in cardiac cases when measuring both the aortic root and radial artery pressures, they should have the same MAP, but the radial artery will have an increased SBP and decreased DBP.

Answer 246

Many factors predispose to breech presentation. Abnormalities of the fetus or the maternal pelvis or uterus may play a role. Factors associated with breech presentation include multiparty, multiple gestations, hydramnios, macrosomia, pelvic tumors, uterine anomalies, pelvic contracture, hydrocephalus, anencephaly, previous breech delivery, preterm gestation, oligohydramnios, cornual-fundal placenta, and placenta previa.

Answer 247

The vertebral arteries most commonly originate from the subclavian arteries and are divided into four segments depending on their anatomic location. They traverse the neck anterior to the scalene muscle and enter the vertebral foramina of the sixth cervical vertebra. It can be a site for inadvertent arterial injection when performing an interscalene nerve block.

Answer 248

Absolute contraindications to the use of BPAP in the postoperative period include: - Cardiac or respiratory arrest - Severe agitation - Voluminous secretions/vomiting/GI bleeding - Inability to protect airway - Facial trauma - Hemodynamic instability Specifically, recent upper gastrointestinal stapling is not a contraindication to the use of BPAP assuming that standard precautions are taken (peak airway pressures 25 cmH2O and PSV below 6-8 cmH2O). In such cases, a nasogastric tube may be in place which can be leveraged to assess for abdominal insufflation. If this tube is placed on a bag instead of to constant suction, insufflation of the bag will indicate insufflation of the stomach and upper gastrointestinal tract during BPAP ventilation, and would likely indicate a need for conversion to endotracheal intubation in this patient population.

Answer 249

Gabapentin reduces the release of glutamate by binding to the α2-δ subunit of voltage-gated calcium channels. Decreased glutamate release decreases the production of the pain mediator substance P, thereby decreasing neuronal transmission of pain signals. There is also decreased activation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors on noradrenergic synapses, which attenuates the sympathetic response to pain.

Answer 250

NMDA receptors are antagonized by ketamine. NMDA antagonism reduces the release of glutamate. Magnesium is another NMDA antagonist.

Answer 251

The primary cause of fetal bradycardia is increased parasympathetic activity via the vagus nerve in the setting of fetal hypoxia

Answer 252

``` parasympathetic tone (which increases with term age) Variability of FHR is a subjective measure of the FHR tracing but is defines as cyclical fluctuation of the FHR at least twice per minute. This is primarily influenced by the parasympathetic tone, with increasing tone exerting an increased effect on the heart rate, and therefore increasing variability. ```

Answer 253

LIttle--not mature sympathetics NS; Atropine decreases variablity (less parasympathetic tone) maternal administration of atropine, which effectively eliminated the vagal tone in the fetus as it readily crosses the placenta, causes a decrease in FHR variability. Conversely, maternal administration of a beta-blocker which also readily crosses the placenta has minimal effect on the FHR variability. This is due to the minimal impact of the immature fetal sympathetic nervous system on regulating FHR.

Answer 254

hypoxia CNS injury/ Anacephaly maternal opioid use fetal sleep state

Answer 255

Early decelerations are defined as a decrease in FHR of typically no less than 20 bpm below baseline and occur simultaneously with contractions. These are thought to be due to reflex vagal stimulation and are in general considered to be a benign finding.

Answer 256

Late decelerations are also associated with uterine contractions but are slightly delayed in their onset (10-30 seconds following the onset of contractions). These are thought to represent a response to fetal hypoxemia, with traditional teaching implicating some form of placental insufficiency. By themselves, late decelerations are of uncertain clinical significance, but in combination with decreased variability, this finding may point towards fetal compromise.

Answer 257

Variable decelerations are variable in their presentation but typically result in a more profound deceleration of FHR than the other two. These are thought to be due to occlusion of the umbilical cord during contractions. While healthy fetuses can typically tolerate transient variable decelerations, prolonged fetal bradycardia impairs the ability of the fetus to maintain cardiac output and is an indication to consider emergent operative delivery.

Answer 258

The following medications cross the placenta following maternal administration and may impact the physiology of the fetus seen on monitoring: morphine, fentanyl, benzodiazepines, ephedrine, local anesthetics, atropine, beta-blockers.

Answer 259

The gold standard laboratory analysis of platelet function is optical aggregometry, though viscoelastic monitoring of coagulation is a reasonable surrogate if the appropriate assays are utilized. Other point-of-care measures of platelet function are limited in their use to predict an increased risk of intraoperative bleeding.

Answer 260

``` Plateaued EXPIRation (flat top) A variable INTRAthoracic airway obstruction (e.g. distal tracheal tumor or mediastinal mass) produces a flow-volume loop with a plateaued EXPIRATORY curve and the flow rate is usually decreased. During expiration, intrathoracic pressure becomes positive which further decreases the airway diameter, enhances the degree of obstruction, and impairs airflow. The inspiratory curve is usually normal since the negative intrathoracic pressure generated during inspiration helps keep the airway open. ```

Answer 261

``` Plateued INSPIRation (flat bottom) A variable EXTRAthoracic airway obstruction (e.g. proximal tracheal tumor, external compression from a goiter) produces a flow-volume loop with a plateaued INSPIRATORY curve, and the flow rate is usually decreased. During inspiration, the negative inspiratory pressure causes the obstruction to increase. The expiratory curve is usually normal since the positive airway pressure generated during expiration helps keep the airway open ```

Answer 262

Plateued top and bottom A fixed upper airway obstruction or fixed large airway obstruction (e.g. foreign body, tracheal stenosis, large airway tumor) impairs BOTH inspiration and expiration leading to a flow-volume loop with plateaued and decreased inspiratory and expiratory flows.

Answer 263

SCooped out expiration portion (top) (COPD) is characterized by an expiratory phase with a quick peak followed by a much lower than normal plateau phase. This is representative of the dynamic, intrapulmonary airway obstruction that occurs with COPD during exhalation. The inspiratory phase is usually normal

Answer 264

Common tocolytics include magnesium, terbutaline, and ritodrine (not available in the United States).

Answer 265

Common early symptoms include nausea, headache, lightheadedness, and muscle weakness. Hyporeflexia or lack of deep tendon reflexes, sedation, and hypotension suggest higher levels of magnesium. Marked levels of hypermagnesemia can lead to respiratory arrest and cardiac arrest. Treatment includes discontinuation of the magnesium infusion/intake and administrating intravenous calcium. Loop diuretics and intravenous fluids can also be used to enhance excretion of magnesium.

Answer 266

The cytochrome P450 (CYP) superfamily of enzymes is responsible for most of the phase one biotransformation reactions in the liver. The phase one reactions include oxidation (primary), reduction, and hydrolysis. The enzymes are highly concentrated in hepatocytes and in the small intestines but also are found in small amounts in the lungs, kidneys, and skin. There are multiple subtypes of CYP enzymes, including 3A4, 2D6, 2C9, 2C19, and 2E1.

Answer 267

slows it down (p450 inhibitor) Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) that is used in the treatment of both generalized anxiety disorder and major depressive disorder. Fluoxetine and its metabolite norfluoxetine inhibit CYP 3A4, which is responsible for the metabolism of many anesthetic drugs, including midazolam

Answer 268

methylergometrine make the blood pressure go HYER (higher): HY ER: metHYlERgometrine HYpERtension Also, the double O's go together: OOS: carbOprOSt brOnchOSpasm

Answer 269

Uterine atony is a common cause of post-delivery hemorrhage. In patients who have a diagnosis of preeclampsia (as this patient is presumed to have), administration of methylergometrine should occur only after all other options are exhausted and with extreme caution. Methylergometrine is an ergot alkaloid that is typically given intramuscularly. It has an effect within 10 minutes and lasts 3-6 hours. It can lead to intense vasoconstriction, especially if accidentally given intravenously. This can cause significant morbidity (e.g. stroke) in patients with preexisting hypertension or preeclampsia.

Answer 270

Carboprost is a prostaglandin, which increases the force and frequency of uterine contractions. It is typically given intramuscularly and can be repeated at 15-90 minute intervals for a maximum of 8 doses.

Answer 271

One of the most important factors in determining the clinical pharmacology for a particular opioid is its degree of lipophilicity versus hydrophilicity. Cephalad movement of opioids in the CSF principally depends on lipid solubility. Highly lipid-soluble opioids are limited in their cephalad migration by uptake into the spinal cord, whereas less lipid-soluble opioids remain in the CSF and transfer to more cephalad locations. Hydrophilic opioids, like morphine, have the potential to produce a delayed, but longer duration of analgesia, along with a generally higher incidence of side effects because of cephalic or supraspinal spread.

Answer 272

Vascular rings should be considered in the differential diagnosis for airway compression, wheezing, stridor, respiratory distress, apnea, cyanosis, and dysphagia. MRI or CT should be employed to assess the level of branching, which will affect surgical planning. Mirror branching consists of a right-sided aortic arch that gives rise to a left brachiocephalic artery, which then gives rise to a left subclavian artery and left carotid artery. These patients should be extubated with caution and vocal cord paralysis may be seen.

Answer 273

Omalizumab is a monoclonal anti-IgE antibody. It is used as an antihistamine anti-inflammatory for patients with severe asthma.

Answer 274

leukotriene modifier

Answer 275

The Parkland formula calls for 4 mL of crystalloid / kg / % burn in the first 24 hours. The modified Brooke formula calls for 2 mL of crystalloid / kg / % burn in the first 24 hours. For both of these, half of the calculated predicted volume is given over the first eight hours, 25% is given over the next eight hours, and the last 25% is given during the final eight hours. The Joint Trauma Service rule of tens calls for an initial hourly rate of 10 * % burn (for patients 40-80 kg; for every 10 kg over 80 kg, an additional 100 ml/hr is added). In each case, the infusion rate should be regularly titrated (e.g. hourly) based on clinical response.

Answer 276

Diffusion hypoxia ("Fink effect") is a well-documented effect since the 1950s that can be observed following the cessation of an inhaled anesthetic involving the use of high concentrations of nitrous oxide. The relatively higher concentrations of nitrous oxide (up to 70%) required to maintain general anesthesia compared to other more potent inhaled anesthetics, and its low blood solubility result in the rapid alveolar elimination of large amounts of nitrous oxide following cessation of the anesthetic. This flooding of nitrous oxide results in the displacement of oxygen and carbon dioxide in the alveoli, leading to a temporary hypoxia. This diffusion hypoxia typically lasts for 5-10 minutes immediately after emergence, and can be prevented by the use of supplemental oxygen while the nitrous oxide is being eliminated.

Answer 277

Nitrous oxide has a relatively low blood:gas coefficient of 0.47, which explains its property as a quick onset/offset inhaled anesthetic. This is in contrast to isoflurane, which has a much slower onset of action and elimination with its blood:gas coefficient of 1.4. In other words, isoflurane is nearly 3 times more soluble in blood compared to nitrous oxide. This results in a slower increase in alveolar isoflurane concentration because the anesthetic is rapidly removed from the alveoli into the bloodstream. In contrast, a less blood soluble anesthetic like nitrous oxide or desflurane results in a faster increase in alveolar concentration because the anesthetic is removed less quickly from the alveoli into the bloodstream. Similarly, less blood soluble anesthetics are eliminated faster from the blood into the alveoli when the anesthetic is discontinued. While it may appear counter-intuitive at first, it is important to understand this relationship between an inhaled anesthetic's blood:gas coefficient as it relates to the speed of onset/offset.

Answer 278

Diffusion hypoxia is a well-known phenomenon that can occur following administration of nitrous oxide as part of general anesthesia. The low blood solubility of nitrous oxide, coupled by relatively low potency leads to large amounts of nitrous oxide being eliminated into the alveoli over a short period of time following cessation of anesthesia. This leads to displacement of oxygen and carbon dioxide in the alveoli. Supplemental oxygen should be provided to mitigate this effect.

Answer 279

Lung abscesses are most commonly a result of primary lung infections, such as aspiration pneumonia, leading to further necrosis and abscess formation. Organisms that are commonly implicated include anaerobes (Bacteroides, Peptostreptococcus), as well as some aerobes (Staphylococcus, Klebsiella, and Pseudomonas).

Answer 280

At clinical doses, etomidate exerts its effect at the γ-aminobutyric acid type A (GABAA) receptor by binding to specific sites on the receptor which enhances the affinity for GABA binding. The principle inhibitory neurotransmitter in the central nervous system is GABA. GABA-A receptors are included in a class of receptors known as cys-loop ligand-gated ion channels composed of five subunits (two α, two β, one γ) and selectively conduct chloride ions. The activation of GABAA receptors leads to hyperpolarization of the neuron significantly below the resting Nernst potential of -70 mV and the sedative-hypnotic effects of the GABAA agonists. Other inhibitory neurotransmitters include glycine, adenosine (A2A receptor), norepinephrine (α2), and opioids. Other GABAA agonists include benzodiazepines, barbiturates, propofol, and volatile agents.

Answer 281

Etomidate is a potent GABAA receptor agonist that leads to neuron hyperpolarization via positive modulation of the receptor for GABA binding. Etomidate is highly protein bound (~75%) and metabolized by liver ester hydrolysis to inactive metabolites that are primarily excreted by the kidneys. It does not inhibit sympathetic tone or myocardial function to a significant degree, and does not blunt the sympathetic response to laryngoscopy and intubation. Infusions are typically avoided due to adrenal suppression. Cerebral perfusion pressure is maintained. However, like other GABAA agonists, it does reduce the cerebral metabolic rate of oxygen and cerebral blood flow (and therefore intracranial pressure).

Answer 282

Ketamine, nitrous oxide, methadone, and memantine are examples of NMDA receptor antagonists.

Answer 283

Clonidine and dexmedetomidine are examples of α2 agonists.

Answer 284

If the chest wall or pleura are violated, air can escape into the pleural space, resulting in a pneumothorax. Occasionally, a "one-way valve" effect may occur, resulting in a gradual build-up of pressure in the pleural space and compression of the great vessels leading to hemodynamic collapse. Patients may present with progressively worsening tachycardia, tachypnea, hypoxia, and hypotension. Late findings include a deviated trachea and a mediastinal shift away from the side of the tension pneumothorax. Without immediate treatment, the patient may develop pulseless arrest. Either the 5th intercostal space in the anterior axillary line or the 2nd intercostal space in the mid-clavicular line may be used for needle decompression. Needle insertion should be at the superior border of the rib to avoid the intercostal neurovascular bundle, and successful placement should result in a hiss of escaping air and improvement in patient hemodynamics.

Answer 285

Gray rami communicantes originate from adjacent paravertebral ganglia of the sympathetic trunk and contain postganglionic nerve fibers of the sympathetic nervous system. Gray rami are composed largely of unmyelinated neurons. White rami communicantes, on the other hand, are heavily myelinated neurons and give the rami their white appearance. Helpful mnemonic: whIte on the way Into the sympathetic trunk, grEy Exiting the sympathetic trunk.

Answer 286

The medulla is known to house the central respiratory system, which is chemically sensitive to dissolved carbon dioxide as bicarbonate does not permeate the blood-brain barrier. Two groups of neurons in the medulla control basic respiratory rhythm. These are categorized as the dorsal and ventral respiratory group. The ventral respiratory group is active during expiration. Meanwhile, the dorsal respiratory group is active during inspiration and is regulated by the pons.

Answer 287

Cerebral perfusion pressure is equal to mean arterial pressure - intracranial pressure (CPP = MAP - ICP). Cerebral autoregulation is typically compromised during brain injury. Cerebral perfusion pressure then becomes directly dependent on MAP and inversely dependent on ICP.

Answer 288

Brown fat tissues and skeletal muscles are the major sources of nonshivering thermogenesis in adults.

Answer 289

The Chi-square test is a statistical option to determine the probability of an observed distribution occurring due to chance alone. It is often referred to a "goodness of fit" measurement because it evaluates how well the observed distribution of data fits with what the expected distribution would be if variables were truly independent. Categorical data is well suited for analysis by a Chi-square test.

Answer 290

Dead space is the proportion of tidal ventilation that does not participate in gas exchange because it does not come in contact with the pulmonary capillary blood flow. It is divided mainly into anatomical dead space and alveolar dead space. The sum of these makes up the physiologic dead space, which is calculated using the following formula known as the Bohr equation. Vd = Vt*(PACO2-PECO2)/PACO2 (Vd: dead space, Vt: tidal volume, PACO2: mean alveolar partial pressure of CO2, PECO2: mixed expired partial pressure of CO2)

Answer 291

Beta blockers and the calcium channel blocker diltiazem are the current drugs of choice for the pharmacologic management of new-onset AF in hemodynamically stable patients. Patient co-morbidities can help the provider determine which agent (beta blocker or calcium channel blocker) to choose. Additionally, amiodarone is not considered a first-line agent in the management of atrial fibrillation. Dont give BB to peopel with COPD or DM

Answer 292

Abdominal compartment syndrome is diagnosed by observing a tense, distended abdomen and by obtaining bladder pressure readings > 20-25 mm Hg via a urinary catheter. Abdominal compartment syndrome has a high rate of morbidity and mortality and therefore necessitates prompt recognition and surgical decompression to avoid multiorgan failure and death.

Answer 293

The following are characteristics of Line isolation Monitors (LIM): 1) Monitors the integrity of the ungrounded power source in the operating room. 2) The primary circuit is attached to ground, but the secondary circuit is not. 3) The LIM alarms when the leakage current is greater than 5 milliamps. 4) A first fault is not a shock hazard, but a second fault is a hazard to operating room personnel. If there is an alarm after the procedure has begun, the most appropriate next step is to unplug the electrical device which was most recently plugged in.

Answer 294

A variety of antiepileptic agents are currently used for management of seizure disorders. However, only ethosuximide is used exclusively for the treatment of absence seizures. Its mechanism involves blockade of T-type calcium channels (which possess a corticothalamic distribution), resulting in a reduction in excessive excitatory activity.

Answer 295

Yes The BBB protects the CNS from pathogens and rapid fluctuations in its electrolyte-fluid balance. Water moves freely across the blood-brain barrier (BBB) based on the tonicity of intravascular fluid. With the pathologic disruption of the BBB, hydrostatic pressure becomes more central to intracranial fluid movement.

Answer 296

Mannitol is a sugar alcohol with osmotically active properties. It is given to promote diuresis in situations such as the oliguric phase of acute renal failure, elevated intraocular pressure, and elevated intracranial pressure. Mannitol is also useful in flushing out harmful toxins. Its utility in elevated intracranial pressure stems from its large molecular weight, which makes it unable to penetrate the BBB. Mannitol then draws fluid from the brain into the intravascular space, which is then excreted as urine.

Answer 297

YES Certain drugs with the same function may differ in CNS permeability because of the BBB such as in the case of anticholinergic medications glycopyrrolate (does not cross BBB, does not cause sedation) and atropine (does cross BBB, does cause sedation).

Answer 298

Flumazenil has the shortest elimination half-life of all currently used benzodiazepines, which makes recrudescence of sedation after a single administration of flumazenil likely.

Answer 299

Fentanyl has NOT been shown to cause intrathecal (IT) granuloma formation when chronically administered via an intrathecal drug delivery (ITDD). Administration of both hydromorphone and morphine in ITDD systems is associated with the formation of IT granuloma which causes pump malfunction, neurologic deficits, and may require surgical excision.

Answer 300

- Beta waves (awake) - Alpha waves (drowsy) - Theta waves (stage 1) - Spindles and K complexes (stage 2) - Delta waves (stage 3 and 4) - then back to Beta waves (awake) Note that the oscillation frequency starts high then progresses lower.

Answer 301

``` Name Frequency Range (Hertz, Cycles per Second) Slow < 1 Delta 1 to 4 Theta 5 to 8 Alpha 9 to 12 Beta 13 to 25 Gamma 26 to 80 ```

Answer 302

Acetylcholine (ACh) is synthesized in the presynaptic terminal by acetylation of choline with acetyl-CoA via choline acetyltransferase in the cytoplasm.

Answer 303

Acetylcholine (ACh) is synthesized in the presynaptic terminal by acetylation of choline with acetyl-CoA via choline acetyltransferase in the cytoplasm. Large amounts of ACh molecules are then stored together within vesicles near the cell membrane. After propagation of an action potential (via sodium channels), there is activation of voltage-gated calcium channels at the nerve terminal and calcium influx leading to "docking" of the ACh vesicles to SNARE proteins. The two fuse and ACh is released via exocytosis. A portion of the ACh molecules activate the nicotinic acetylcholine receptors, although a large amount of ACh is rapidly metabolized by acetylcholinesterase to form acetate and choline. Choline is recycled back into the nerve terminal.

Answer 304

Acetylcholine is rapidly broken down by acetylcholinesterase in the synapse into acetate and choline. Choline is recycled back into the presynaptic neuron. Unlike norepinephrine, there is no reuptake of acetylcholine and it must be synthesized constantly.

Answer 305

No As described in the American Society of Anesthesiologists (ASA) Guidelines for Office-Based Anesthesia, all locations that utilize triggering agents (succinylcholine and volatile anesthetics) for the administration of anesthesia are required to maintain on-site medications, protocols, and procedures for the effective management of malignant hyperthermia. If these agents are not utilized, then the office is not required to maintain these resources.

Answer 306

The hyperglycemia of diabetes leads to the non-enzymatic glycosylation of small vessel endothelium, which leads to ischemia in axonal nerve tissue (microangiopathy) and elsewhere.

Answer 307

Physiologic dead space equation: VD/VT = (PaCO2 - PECO2) / PaCO2

Answer 308

Hexamethonium is an example of a ganglionic blocking drug which acts as an antagonist at the neuronal-type nicotinic receptors.

Answer 309

Transcranial Doppler (TCD) ultrasound monitoring measures two parameters during carotid vascular surgical procedures: blood flow velocity in major arteries (normally the middle cerebral artery [MCA]) that lead to the cerebral cortex, as well as the number of atherosclerotic emboli detected in the same vessel.

Answer 310

Reduced cardiac output leads to an increased speed of inhaled anesthetic induction (FA/FI), particularly for the soluble anesthetics like isoflurane or halothane.

Answer 311

endocardium

Answer 312

Cardiac effects of bupivacaine with epinephrine include an increase in the PR interval, increased duration of the QRS complex, increase in T-wave amplitude, ST-segment changes, sinus bradycardia, and sinus arrest. Bupivacaine-induced T-wave elevation is a sign of impending cardiac toxicity, especially during fast injection

Answer 313

Injection of bupivacaine with epinephrine can cause QRS complex widening, PR interval lengthening, and QTc interval lengthening.

Answer 314

Tissues possess both static and dynamic compliance. Compliance, in general, can be thought of as ΔV/ΔP. The Cstat of a tissue can be measured during an inspiratory hold. The formula uses plateau airway pressures since the value is measured during periods of no flow. The formula is Cstat = VT/(Pplat-PEEP).

Answer 315

Dynamic compliance refers to compliance of lung tissue during gas flow. It can be calculated using the formula: Cdyn = VT/(PIP - PEEP). Decreases in dynamic compliance are observed in a variety of obstructions, such as obstruction of the endotracheal tube, mucous plugging, or airway narrowing. Keep in mind: because PIP is always higher than Pplat, the Cdyn for any given lung tissue is always lower than the Cstat.

Answer 316

Opioid receptors remain a topic of continued research. It is known that they are G protein-coupled receptors with several subtypes, some of which are still being elucidated. The µ-, κ-, and δ-receptor subtypes are well-characterized. Each is found throughout the body in variable distribution and are responsible for the many effects exerted by both endogenous and exogenous opioids. µ1: supraspinal analgesia, physical dependence µ2: respiratory depression, miosis, euphoria, reduced gastrointestinal motility, physical dependence κ: Spinal analgesia, sedation, miosis, inhibition of antidiuretic hormone release δ: Analgesia, euphoria, physical dependence

Answer 317

Alvimopan is a potent µ-receptor antagonist which does not cross the blood-brain barrier. It is used to help prevent postoperative ileus while allowing continuation of pain management with opioids.

Answer 318

Patients with heart failure with preserved ejection fraction (HFpEF) have EF greater 50% with a normal left ventricular end-diastolic volume and an elevated left ventricular end-diastolic pressure. Concentric remodeling and left ventricular hypertrophy from long-standing hypertension contribute to abnormalities in diastolic function such as a delayed and slowed relaxation, decreased recoil, slow and incomplete early filling, increased filling during atrial contraction, and decreased distensibility.

Answer 319

ALPHA-1 The postjunctional nicotinic acetylcholine receptor is a pentamer consisting of 2 alpha-1 subunits, a beta-1 subunit, a delta-7 subunit, and an epsilon subunit (gamma subunit instead of epsilon subunit in the fetal receptor). The acetylcholine binding site is on the alpha-1 receptors.

Answer 320

EEG monitoring is a reliable and widely used method of confirming brain death, but can only be used as an ancillary test after standard criteria have been met. Although EEG confirmation is reliable and widely used, it is an ancillary test and not mandatory. Electrocerebral silence on EEG (< 2 uV/mm activity) is confirmatory, especially when combined with evoked responses, but a false positive may occur with high doses of anesthetics such as barbiturates.

Answer 321

acute cerebral edema Tight hemodynamic control is paramount in AVM embolization procedures. Cerebral dysautoregulation can result in rapid and profound cerebral edema in the downstream vascular distributions. This edema may require rapid action on the part of the anesthesiologist consisting of therapeutic hypotension, hypocapnia, hypothermia, or administration of sedative-hypnotic agents such as barbiturates or propofol.

Answer 322

Adrenal cortex layers are GFR: glomerulosa (mineralocorticoids, "salty"), fasciculata (glucocorticoids, "sweet"), reticularis (reticularis, "sex"). Mnemonic: the deeper you go, the better it gets.

Answer 323

Glucocorticoids, primarily cortisol, acts to increase energy substrates. When stressed, the body needs a surge of energy available to handle the stress response. Cortisol is the primary glucocorticoid that will mobilize energy. Cortisol diffuses through the cell membrane to alter gene transcription. It mobilizes fatty acids, protein catabolism products, and glucose by increasing glucose substrates and impairing insulin sensitivity to decrease the amount of glucose taken up for storage.

Answer 324

A professional liability insurance policy that covers malpractice claims reported during the year the policy is active is known as a claims made policy.

Answer 325

No anesthetic best practice currently exists to prevent POCD. Age greater than 65 years old has been independently shown to predict the development of POCD. No other risk factors for POCD have been definitively identified. No difference in POCD has been seen with a regional versus general anesthetic technique, nor is there any single anesthetic drug that has been identified as either causative or protective.

Answer 326

Motor innervation of the tongue arises nearly entirely from the hypoglossal nerve (CN XII). The hypoglossal nerve innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus which is innervated by the vagus nerve. It is a nerve with a solely motor function. The hypoglossal nerve controls the tongue movements required for speech, swallowing, and moving the tongue side to side. Damage to the nerve can affect the tongue's ability to move.

Answer 327

The glossopharyngeal nerve provides both taste and sensory innervation to the posterior 1/3 of the tongue.

Answer 328

The recurrent laryngeal nerve innervates the larynx below the vocal cords and the trachea. The recurrent laryngeal nerve provides the motor supply to all intrinsic laryngeal muscles except for the cricothyroid muscle. The cricothyroid muscle receives motor innervation from the external branch of the superior laryngeal nerve. Because the recurrent laryngeal nerves supply all of the intrinsic muscles of the larynx (with the exception of cricothyroid muscle), trauma to these nerves can result in vocal cord dysfunction.

Answer 329

The superior laryngeal branch of the vagus nerve divides into an external (motor) nerve and an internal (sensory) laryngeal nerve that provide sensory supply to the larynx between the epiglottis and the vocal cords. The cricothyroid muscle receives motor innervation from the external branch of the superior laryngeal nerve.

Answer 330

Overdose Pouring isoflurane into a sevoflurane vaporizer is most likely to lead to an overdose of volatile anesthetic. This is due to (1) the larger vapor pressure of isoflurane, and (2) the increased potency of isoflurane compared to sevoflurane. Sevoflurane has a relatively low vapor pressure of 160 mmHg at 20 °C compared to 240 mmHg for isoflurane. Therefore, there will be proportionally more molecules of isoflurane in the vapor phase and the output concentration of isoflurane will be greater than what is set on the "sevoflurane" vaporizer concentration dial. The use of an anesthetic agent analyzer (e.g. infrared absorption spectrophotometry) would alert the provider to such an error.

Answer 331

Increased P50 values actually correspond with a decreased affinity of hemoglobin for oxygen. More oxygen offloading occurs in this situation. The P50 (normally 27 mm Hg) is the partial pressure of oxygen (PO2) at which the hemoglobin (Hgb) molecule is 50% saturated with oxygen at 37 degrees Celsius and a pH of 7.4. Factors influencing the P50 are directly related to those parameters that shift the oxygen-hemoglobin dissociation curve to the "left" or to the "right". The P50 is reduced when the curve is shifted to the left for the following reasons: hypothermia, alkalosis, decreased DPG. A decreased P50 results in an increased Hgb affinity for oxygen, leading to a release of oxygen to the tissues at a lower PO2. The P50 is increased when the curve is shifted to the right due to: hyperthermia, acidosis, increased DPG. An increased P50 results in a decreased Hgb affinity for oxygen and release of the oxygen to the tissues at a higher PO2.

Answer 332

P50 is normally ~27 mm Hg and corresponds to the PO2 at which 50% of Hgb is saturated at normal physiologic pH and temperature. A left shift (due to hypothermia, alkalosis, decreased DPG) causes a decreased P50 and an increased Hgb affinity for oxygen. A right shift (due to hyperthermia, acidosis, increased DPG) causes an increased P50 and a decreased Hgb affinity for oxygen, meaning more offloading of oxygen.

Answer 333

Decreasing the tidal volume to 6 mL/kg (lung protective strategy) could decrease the risk of renal injury related to positive pressure in this patient by decreasing cytokine release.

Answer 334

Renal effects from mechanical ventilation involve three broad categories: hemodynamic, neurohormonal, and biochemical. Induction of positive pressure ventilation affects hemodynamics by decreasing preload and increasing right ventricular afterload (both of which decrease cardiac output and renal blood flow), while promoting increased venous pressure, all of which have deleterious effects on the kidneys. Positive pressure ventilation also results in an increase in sympathetic nervous system output which secondarily results in an increase in renin release through beta-1 receptor stimulation with resultant release of angiotensin-2 and aldosterone. This results in vasoconstriction with salt and water retention which can decrease urine output. There is also an increase in the release of ADH (also seen with surgical stress) which increases free water reabsorption and decreases urine output, however this is a minor component. Lastly, there is a decrease in atrial natriuretic peptide which decreases natriuresis and vasodilation. Biochemically, positive pressure ventilation induces cytokine release which can cause endothelial activation, increase vascular permeability, and result in apoptosis of renal epithelial cells. The pattern of ventilation can have alterations in the amount of cytokine release and resultant renal injury as described earlier with the ARDSnet trial. There is also evidence that positive pressure ventilation increases the release of nitric oxide and enhances nitric oxide synthase activity. The breakdown products of nitric oxide cause oxidative damage, increased vascular permeability and can result in cellular apoptosis.

Answer 335

Contraindications: - Coagulopathy. - Inability to identify landmarks (obesity, thyroid goiter, distorted anatomy). - Laryngeal disease (such as laryngeal stenosis directly at the puncture site. Retrograde intubation has successfully been used in epiglottitis, laryngeal trauma, laryngeal cancer). - Local infection (such as pre-tracheal abscess).

Answer 336

The following table lists approximate changes with pregnancy. Cardiac Output Increased 40-50% Heart Rate Increased 15-25% Stroke Volume Increased 30% Intravascular Volume Increased 35% Central Venous Pressure No Change Plasma Volume Increase 45% Red Blood Cell Mass Increased 20% Systemic Vascular Resistance Decreased 15-20%

Answer 337

Both increased carbon dioxide tension and volatile agents increase cerebral blood flow (CBF), while the latter also decreases cerebral metabolic rate (CMR). Volatile agents delivered at levels greater than 1 MAC decrease CMR but increase CBF, known as uncoupling. This decreased neuronal metabolic demand with increased metabolic supply is called luxury perfusion. Although this can be beneficial during global ischemia, the excess blood flow to certain regions steals from other regions which can be detrimental during focal ischemia.

Answer 338

The brain receives 10-15% of the total cardiac output, or blood flow of approximately 50 mL/100 g/min. At rest, the cerebral metabolic rate of oxygen (CMRO2) is approximately 3.5 mL/100 g/min.

Answer 339

Nitrous oxide (N2O) increases CBF, CMR, and subsequently ICP, though these effects differ depending on whether it is administered alone or with other agents.

Answer 340

Hypocapnia causes cerebral vasoconstriction, which was thought to be able to redirect blood flow from normal regions to ischemic regions: the so-called “Robin Hood phenomenon” or inverse steal.

Answer 341

Cerebrospinal fluid (CSF) lacks protein, which allows flow of fluid into the protein-rich systemic venous system.

Answer 342

CSF flows from the ventricles of the brain into the subarachnoid space to provide buoyancy, clear waste, and protect the central nervous system (CNS) from trauma. Adult humans produce 21 mL/hr of CSF, which amounts to 500 mL a day. Most of this is completed by the choroid plexus although the lateral ventricles also produce a significant amount. CSF movement is pulsatile, driven by the arterial pulsations of the brain in a non-unidirectional flow.

Answer 343

Sodium bicarbonate is the standard initial therapy for tricyclic antidepressant (TCA) toxicity. The primary mechanism of action of TCAs is the inhibition of presynaptic neurotransmitter uptake (mostly norepinephrine and serotonin). Side effects are mainly related to the antimuscarinic properties and include dry mouth, dry nose, blurry vision, constipation, and urinary retention. Overdose, however, can lead to serious cardiovascular and neurological consequences. TCA overdose can lead to severe cardiotoxicity manifesting with ECG changes such as QRS widening with the possibility of degenerating into a lethal arrhythmia. After evaluating the patient’s airway, breathing, and circulation, sodium bicarbonate is the standard initial therapy for TCA toxicity.

Answer 344

While the mechanism of action of dexamethasone’s antiemetic effects remain unclear, it likely involves central inhibition of the nucleus tractus solitarii.

Answer 345

Emergence delirium is most common in children aged 2-5 years who undergo a painful surgical procedure under general inhalational anesthesia. It is characterized by inconsolability, incoherence, thrashing, screaming, and/or crying. The incidence of emergence delirium can be decreased by prophylactic administration of clonidine, dexmedetomidine, fentanyl, ketamine, nalbuphine, or propofol.

Answer 346

Refeeding syndrome causes hypophosphatemia, hyponatremia, hypocalcemia, hypomagnesemia, hypokalemia, and hyperglycemia.

Answer 347

Maternal NSAID use is associated with premature closure of the ductus arteriosus. Prostaglandins keep the ductus open, PGE-1 is used after birth to keep ductus open in ductus-dependent congenital cardiac conditions. Because of the potential for premature ductus arteriosus closure, NSAIDs are discontinued several weeks before term gestation.

Answer 348

Hypoxemia, hypothermia, and acidosis are all associated with persistent fetal circulation. This is due to increased pulmonary pressures, which favors flow through shunts that are only functionally closed and not yet anatomically closed.

Answer 349

Type II pneumocytes in the alveolus have a primary function of producing surfactant, which helps to prevent atelectasis. Secondarily these cells may also differentiate into Type I pneumocytes, which then contribute to gas exchange at the alveolar surface.

Answer 350

Reasons for emergent dialysis include AEIOU: Acidosis, Electrolytes, Ingestions (toxins), Overload, Uremia.

Answer 351

The DLCO uses carbon monoxide diffusion to assess the parenchymal function of the lungs. DLCO is effected by cardiac output and hemoglobin concentration. The DLCO is elevated in conditions like: asthma, polycythemia, pulmonary hemorrhage, exercise, and left to right shunts. It is decreased in pulmonary embolism.

Answer 352

The 4T clinical scoring system is used to clinically diagnose HIT prior to laboratory confirmation. The 4Ts include: 1) Thrombocytopenia 2) Timing of the reduced platelet count 3) Presence of Thrombosis 4) The exclusion of other causes for thrombocytopenia

Answer 353

Hypercalcemia leads to "stones, bones, abdominal groans, thrones, and psychiatric overtones" Stones: kidney stones Bones: bone-related complications Groans: gastrointestinal symptoms Thrones: polyuria, constipation (throne = toilet) Overtones: central nervous system effects

Answer 354

Mechanisms of action of medications for aspiration prophylaxis: Metoclopramide - increases LES tone and gastric emptying. Ranitidine and other H2 antagonists - decreases both the amount and acidity of gastric secretions. Sodium citrate - decreases the acidity of gastric contents.

Answer 355

Acute ST elevation represents transmural myocardial injury whereas ST depression represents subendocardial ischemia. Recognition is important as treatment strategies between the two are different.

Answer 356

A hypochloremic metabolic alkalosis is classically found in newborns with pyloric stenosis due to significant acid and chloride loss from emesis. Other etiologies include, but are not limited to: cystic fibrosis, diuretic-induced alkalosis or diuretic abuse (namely loop or thiazide diuretics), laxative abuse, recurrent vomiting, excessive gastric acid loss (such as with prolonged nasogastric tube suctioning), and post-hypercapnic metabolic alkalosis.

Answer 357

The ideal leak pressure of an uncuffed ETT in pediatric patients is 20-30 cm H2O. If a leak pressure >40 cm H2O is measured, the ETT should be replaced with a smaller size.

Answer 358

Nitrous oxide (C) should be avoided in patients with MTHFR deficiency. Nitrous oxide directly inhibits methionine synthetase. The MTHFR gene encodes a protein used in the folate pathway and synthesis of purines for DNA. When this pathway is inhibited homocysteine levels rise. Use of nitrous oxide further increases the homocysteine level because of impaired mechanisms of metabolism. Elevated homocysteine increases incidence of thrombosis and adverse coronary events.

Answer 359

hyponatremia Oxytocin is structurally similar to vasopressin and at high doses can decrease urine excretion via antidiuresis independent of volume status. The resultant volume overload is sensed by the atria, which then release atrial natriuretic peptide that promotes natriuresis. In addition, high-dose oxytocin itself stimulates renal natriuresis. Combined, these effects can lead to hyponatremia

Answer 360

Due to structural similarities between oxytocin and vasopressin, high-dose vasopressin administration can cause uterine contractions.

Answer 361

Due to structural similarities between oxytocin and vasopressin, high-dose vasopressin administration can cause uterine contractions.

Answer 362

Carbon monoxide reversibly binds to hemoglobin (Hgb) with 200-300 times greater affinity than oxygen. Accordingly, CO reduces oxyhemoglobin (oxyHgb) concentration by displacing oxygen from the hemoglobin molecule and creates carboxyhemoglobin (COHgb). This leads to a leftward shift of the Hgb-oxygen dissociation curve and reduction in oxygen availability to tissues. This then produces a lactic acidosis due to anemic hypoxia.

Answer 363

Right ventricle is an anterior structure, as is the right coronary cusp. The non-coronary cusp is always located next to the inter-atrial septum.

Answer 364

Resting systolic function is not altered by aging, but exercise-induced increases in cardiac output, stroke volume, and heart rate are reduced. There is an increase in circulating catecholamines with a corresponding desensitization of the β-receptor. Diastolic dysfunction results in a reduction and delay in left ventricular relaxation and therefore reduced passive filling during early diastole. There is an increased reliance on atrial kick for adequate cardiac output.

Answer 365

Perioperative hyperglycemia has been associated with immunosuppression, increased infections, osmotic diuresis, delayed wound healing, delayed gastric emptying, sympatho-adrenergic stimulation, and increased mortality. In addition, it reduces skin graft success, exacerbates brain, spinal cord, and renal damage by ischemia, worsens neurologic outcomes in traumatic head injuries, and is associated with postoperative cognitive dysfunction following CABG.

Answer 366

f a patient’s intrinsic heart rate is higher than the set pacemaker rate when a pacemaker is in an asynchronous mode, R-on-T phenomena may occur leading to ventricular tachycardia or ventricular fibrillatio

Answer 367

The function of modern pacemakers is generally designated using a 3 letter code. The first letter indicates the heart chamber(s) paced, the second is the chamber(s) for which intrinsic electrical activity is sensed, and the third is response to sensing. The presence of an R as a fourth letter means the pacemaker is rate-responsive and will increase its rate, for example, when it senses exercise.

Answer 368

All volatile anesthetics are thought to cause an “uncoupling” of the CBF and CMRO2. They decrease CMRO2 while increasing CBF via a direct cerebral vasodilating effect. TrueLearn Insight : All intravenous anesthetics except ketamine cause a decrease in CMRO2 and a decrease in CBF. Fentanyl has no effect on CMRO2 or CBF.

Answer 369

Hepatic alcohol dehydrogenase converts methanol to highly toxic formaldehyde and formic acid. Treatment of acute methanol poisoning consists of supportive care (securing an airway, maintaining hemodynamic stability, treating metabolic acidosis), prevention of the conversion of methanol to toxic metabolites (ethanol or fomepizole), and in severe cases, rapid elimination of methanol and its metabolites via hemodialysis.

Answer 370

The PT is the best test to measure synthetic function of the liver. The PT is often elevated 1.5 times normal when severe liver disease is present. The PT measures the clotting time of the extrinsic pathway involving factor VII, which has the shortest half-life of the clotting factors.

Answer 371

Fenoldopam is a selective D1 receptor agonist with direct natriuretic and diuretic properties. Fenoldopam promotes an increase in creatinine clearance and has been employed as a renal protector when renal vasoconstriction is anticipated.

Answer 372

hyperglycemia is a side effect of terbutaline. Hyperglycemia is caused by beta agonism in the liver and pancreas. Beta agonism in the liver causes glycogenolysis and beta agonism in the pancreas causes glucagon secretion and suppresses insulin release.

Answer 373

In cirrhotic patients, portal hypertension is often associated with a hyperdynamic circulatory syndrome, with high cardiac output, reduced systemic vascular resistance, and reduced arterial pressure. Vasodilators, such as nitric oxide and carbon monoxide, build up in these patients. Vasoactive intestinal polypeptide is increased as blood is shunted in the intestinal system because of portal hypertension. Additionally, glucagon exists in higher quantities in patients with cirrhosis. Renin also increases...they are intravascularly depeted and high levels of renin, angiotensin, and aldosterone can exacerbate renal dysfunction as they are potent renal artery vasoconstrictors.

Answer 374

Cirrhosis causes a hyperdynamic cardiac state with increased cardiac output and decreased systemic vascular resistance secondary to vasodilating factors (e.g. nitric oxide). The fall in systemic vascular resistance promotes renin release and sodium retention by the kidneys. Additionally, mixed venous oxygen saturation rises with increased cardiac output and AV collaterals.

Answer 375

Aspirin irreversibly inhibits platelet function by blocking the formation of thromboxane A2.

Answer 376

For each day after interruption of any agent which irreversibly inhibits platelet function (aspirin, clopidogrel), approximately 10% to 14% of normal platelet function is restored. Therefore it can take 7 to 10 days for an entire platelet pool to be replenished.

Answer 377

Thrombogenesis (clot formation) includes two processes – platelet aggregation and coagulation. Platelet aggregation includes activation of platelets and subsequent attaching of fibrinogen strands. Coagulation is a complex cascade of events leading to formation of fibrin strands.

Answer 378

There are no contraindications to continuing aspirin therapy when planning neuraxial anesthesia, however the clinician must be aware that when administered in conjunction with other agents which also affect coagulation (such as NSAIDs), this may lead to an increased risk of neuraxial complications.

Answer 379

Clopidogrel is the other commonly prescribed antiplatelet agent which blocks adenosine diphosphate receptors on the platelet membrane inhibiting expression of glycoprotein IIb/IIIa receptors that bind fibrinogen.

Answer 380

Antiplatelet Agents: Aspirin Inhibits thromboxane A2 synthesis Clopidogrel (Plavix) Prasugrel (Effient) Ticagrelor (Brilinta) Inhibit ADP receptor activation Dipyridamole (Persantine) Cilostazol (Pletal) Lowers calcium by elevating cAMP Abciximab (ReoPro) Tirofiban (Aggrastat) Eptifibatide (Integrilin) Blocks GP IIb/IIIa receptors

Answer 381

Anticoagulation Agents: Warfarin (Coumadin) Inhibit vitamin K dependent coagulation factors (II, VII, IX, X) Unfractionated heparin Antithrombin mediated inhibition of serine proteinases Low molecular weight heparin Antithrombin mediated inhibition of serine proteinases Fondaparinux (Arixtra) Antithrombin mediated inhibition of factor Xa Dabigatran (Pradaxa) Direct thrombin inhibition Rivaroxaban (Xarelto) Direct factor Xa inhibition Apixaban (Eliquis) Direct factor Xa inhibition

Answer 382

Respiration is less efficient in infants and the work of breathing can be as much as three times higher than adults. The airway of infants is highly compliant and poorly supported by the surrounding structures. The chest wall is also highly compliant, therefore the ribs provide little support for the lungs; that is negative intrathoracic pressure is poorly maintained. This means that functional airway closure accompanies each breath. The pliable rib cage gives less mechanical support than in the older child or adult, leading to significant retractions with less efficient gas exchange and functional airway closure, thus increasing the work of breathing.

Answer 383

Until the age of 2, infants’ diaphragms have a much smaller proportion of fatigue-resistant type I (slow twitch) muscle fibers. Therefore, infant diaphragmatic and intercostal muscles tire more quickly, as compared to adults, and additional muscle groups need to be recruited. Any factor that increases the work of breathing contributes to early fatigue of the respiratory muscles of infants.

Answer 384

The smaller diameter of infant airways relative to adults causes increased resistance to airflow. This is explained by the Poiseuille law, in which resistance is inversely proportional to the radius raised to the fourth power assuming laminar flow. R = (8 nl) ÷ (π r4) where: R = resistance, n = viscosity, l = length, r = radius.

Answer 385

Oxygen consumption per kilogram is 2-3 times higher in infants as compared to adults (6-7 mL/kg vs. 2-3 mL/kg). To meet this increased need, minute ventilation is accordingly increased.

Answer 386

This patient is developing post-transfusion anaphylaxis which is most likely caused by transfusion of IgA rich blood to a patient who is IgA deficient Supportive care should commence immediately and the transfusion should be discontinued. Intravenous fluids, epinephrine, steroids, and antihistamines should be administered to maintain hemodynamic stability and halt further progression of the anaphylactic reaction. If the patient needed additional transfusions in the future, the patient should receive washed red blood cells which would remove the IgA from the blood.

Answer 387

Normal CVP tracing summary: a wave: atrial contraction, absent in atrial fibrillation c wave: TV bulging into RA during RV isovolumetric contraction x descent: TV descends into RV with ventricular ejection and atrial relaxation v wave: venous return to and systolic filling of the RA y descent: atrial emptying into RV through open TV

Answer 388

Disorder CVP waveform changes Atrial fibrillation Loss of a wave AV dissociation Cannon a wave Tricuspid regurgitation Tall c & v waves; Loss of x descent Tricuspid stenosis Tall a & v waves; Minimal y descent RV ischemia Tall a & v waves; Steep x & y descent; M or W configuration Pericardial constriction Tall a & v waves; Steep x & y descent; M or W configuration Cardiac tamponade Dominant x descent; Minimal y descent

Answer 389

Volatile anesthetics potentiate neuromuscular blockade by DECREASING sensitivity of the postjunctional membrane to depolarization and INCREASING skeletal muscle blood flow which both augment neuromuscular blockade. In addition, potentiation of neuromuscular blockade occurs by depression of upper motor neurons. The order of non-depolarizing muscle relaxant potentiation is desflurane > sevoflurane > isoflurane > halothane > TIVA (e.g. propofol).

Answer 390

Initial steps for anaphylaxis includes (in no certain order): 1. Reducing contact with offending agent: must consider all possible devices in the operating room. Unless you can confirm quickly that the urinary catheter placed does not contain latex, it should be removed 2. Quickly removing all latex items from the surgical field 3. Discontinue all medications that could cause anaphylaxis 4. Maintain the airway and administer 100% oxygen 5. Intubating the trachea (as indicated) 6. Administer 25 mL/kg of intravenous fluids (up to 50 mL/kg) 7. Administer epinephrine: 1 mcg/kg, max dose is code dose of 0.01 mg /kg; adult dose is typically 50-100 mcg IV 8. Discontinue all anesthetic agents

Answer 391

latex allergy Any patient with spina bifida should be considered high risk for latex allergy. These patients have often had multiple surgeries with possible latex exposure. If an anaphylactic reaction does occur, prompt treatment is required to avoid cardiovascular collapse. This includes an IV fluid bolus, epinephrine, prompt removal of possible latex equipment, and cessation of anesthetic agents. A tryptase level should be drawn to assist in the diagnosis.

Answer 392

Separation anxiety does not begin until 6-8 months of age.

Answer 393

Any form of carotid sinus manipulation, such as carotid stent deployment, may result in stimulation of carotid baroreceptors located within the carotid sinus. This results in sympathetic inhibition

Answer 394

The AFFERENT nerve impulses of carotid sinus baroreceptors are transmitted by the Hering’s nerves to the glossopharyngeal nerve (CN IX). Arterial wall stretch at the carotid sinus, within the internal carotid artery, activates the afferent impulse. This activation leads to stimulation of the nucleus tractus solitarius (NTS) in the caudal medulla. The NTS sends excitatory signals to other regions of the medulla which in turn inhibit stimulation of the preganglionic intermediolateral nucleus of the spinal cord which mediates the body’s sympathetic innervation. The NTS may also stimulate vagal nuclei to activate the parasympathetic nervous system via the vagus nerve. These two effects then lead to bradycardia and hypotension.

Answer 395

Carotid body chemoreceptors are located at the bifurcation of the common carotid artery. They primarily monitor the partial pressure of oxygen (PaO2) of blood. These receptors are secondarily sensitive to increases in serum [H+] and PaCO2. They provide afferent information to the central respiratory center regarding oxygen levels. Hypoxia will lead to an increase in respiratory drive. Removal of an atheromatous plaque during a unilateral carotid endarterectomy may lead to denervation of the chemoreceptors, which reduce the ventilation in response to hypoxia. The contralateral carotid body chemoreceptors may compensate for this loss.

Answer 396

Addiction is a behavioral syndrome characterized by evidence of psychological dependence (craving), uncontrolled or compulsive drug use despite harmful side effects, and other drug-related aberrant behavior (e.g. altering prescriptions, manipulating health care providers, drug hoarding or sales, unsanctioned dose escalation).

Answer 397

Acute oliguria is an abrupt decrease in urine output and may be related to prerenal, renal, or post renal dysfunction. Oliguria and progression to acute kidney injury (AKI) is common following cardiac, vascular, and emergency surgery. Laboratory values and clinical evaluation can assist in distinguishing between prerenal, renal, and postrenal etiologies.

Answer 398

Acute postoperative oliguria is most commonly prerenal in nature. Diagnostic criteria include: fractional excretion of sodium less than 1%, BUN/Cr ratio of greater than 20:1, increased serum creatinine, and elevated urine osmolality/specific gravity with a concentrated urine.

Answer 399

Nerve fibers that conduct nociceptive information are A-delta fibers and C fibers. C fibers are small and unmyelinated. A-alpha fibers are large and myelinated. A-alpha fibers carry proprioceptive and motor fibers.

Answer 400

Upon ascent to a high altitude, PaO2 and PaCO2 will significantly drop due to decreased atmospheric pressure and the resultant changes in respiratory drive. The initial hypoxia will trigger peripheral chemoreceptors to promote ventilation (and much more slowly, hematocrit will increase to improve oxygen delivery). However, this leads to a respiratory alkalosis due to increased minute ventilation. An adaptive mechanism to offset this alkalosis is the gradual reduction in plasma bicarbonate (primarily from increased secretion) which is preceded by a decrease in CSF bicarbonate. After 2-3 days of disequilibrium, the stimulation of peripheral chemoreceptors by hypoxia goes unopposed once enough bicarbonate ions have passed into the blood stream from CSF and the pH of the CSF is restored to sea level values.

Answer 401

Prophylaxis may include a “staged ascent” in which several days are spent at increasing heights until the goal is reached. Also, the avoidance of any respiratory depressants is recommended so hypoxic pulmonary drive is not blunted. Acetazolamide (a carbonic anhydrase inhibitor) is a recommended pharmacologic AMS prophylactic measure as it augments the hypoxic ventilatory response promoting urinary bicarbonate loss. Treatment of AMS and its symptoms is primarily by altitude descent but can also include supplemental oxygen administration, dexamethasone administration (though symptoms often return once discontinued), and acetazolamide (especially for AMS-related insomnia).

Answer 402

High altitude pulmonary edema (HAPE) is thought to be caused by increased pressure in the pulmonary vasculature. The increased pulmonary capillary permeability in patients with preexisting pulmonary hypertension may worsen their predisposition to developing HAPE. This is due to the further increase in pulmonary vascular resistance from hypoxic pulmonary vasoconstriction (HPV). Nifedipine and inhaled β2-agonists are used as prophylaxis and treatment to reduce HPV (most vasodilators impair HPV). Treatment strategy includes supplemental oxygen with gradual descent to lower altitudes.

Answer 403

Amiloride is a potassium-sparing diuretic that acts on the distal collecting ducts of the nephron and can cause hyperkalemia. The tubule lumen in this segment is negatively charged with respect to blood and positively charged potassium ions are secreted into the tubule. Potassium-sparing diuretics, such as amiloride and triamterene, block these tubular potassium channels. They exert their diuretic effects by preventing reabsorption of luminal sodium.

Answer 404

Carbonic anhydrase converts carbonic acid to bicarbonate ions and hydrogen ions in the luminal cells. This creates more hydrogen ions to be exchanged and allows for greater reabsorption of luminal sodium. Carbonic anhydrase inhibitors, such as acetazolamide, are a class of diuretics that cause both sodium and bicarbonate ions to be lost in the urine, which can lead to metabolic acidosis

Answer 405

Hypokalemia and hyponatremia can be observed after administration of loop diuretics such as furosemide and bumetanide. These medications exert their effect on the thick ascending loop (TAL) of Henle and prevent sodium reabsorption from the lumen.

Answer 406

A mnemonic for the potassium-sparing diuretics is: "The K+ STAys," for Spironolactone, Triamterene, and Amiloride.

Answer 407

Other electrolyte abnormalities observed with thiazide diuretics include hyponatremia, hypokalemia, and hyperuricemia. Thiazide diuretics have also been associated with hyperlipidemia, hyperglycemia, pancreatitis, jaundice, and aplastic anemia

Answer 408

Helium has similar viscosity to air, but is much less dense, so it can achieve laminar flow High flow tends to be turbulent and density is the more important factor affecting flow. Low density means less turbulent flow (more laminar flow). Low flow tends to be laminar and viscosity is the more important factor affecting flow.

Answer 409

Paradoxical muscular weakness is a risk of neostigmine that has been shown clinically with larger doses or when used following neuromuscular recovery, even when an anticholinergic medication is also used.

Answer 410

There are several major side effects of neostigmine, most of which are attenuated by anticholinergic medications such as glycopyrrolate or atropine. Most effects are due to increased vagal tone such as increased gastrointestinal motility, bradycardia/arrhythmias, and bronchospasm. There is also the potential to worsen neuromuscular weakness if neostigmine is given inappropriately. Clinical evidence confirms that vagal effects are mostly counteracted by the concurrent administration of anticholinergic medications, whereas the paradoxical worsening of neuromuscular weakness is not.

Answer 411

The vagal effects of neostigmine include bradycardia and bradyarrhythmias, bronchospasm, increased gastrointestinal motility, and possibly increased postoperative nausea and vomiting. These can be reversed with concurrent administration of an anticholinergic agent such as glycopyrrolate. Paradoxical muscular weakness is also possible with neostigmine, but appears independent of anticholinergic use.

Answer 412

Nitroglycerin is an appropriate first-line treatment for uterine relaxation for retained placenta.

Answer 413

Respiratory acidosis can occur following respiratory depression or when pulmonary disease causes the lungs to become inefficient at eliminating carbon dioxide. At the root of all causes is an increase in pulmonary artery carbon dioxide concentration (PaCO2). Clinical features of respiratory acidosis depend on the severity and duration of the disease process. In the perioperative period, the most common cause of respiratory acidosis is depression of respiration secondary to medications, which act on the central nervous system (especially opioids). Additionally, residual neuromuscular blockade can result in respiratory depression and hypercarbia. Respiratory acidosis may also occur due to airway obstruction, asthma, pneumothorax, pulmonary edema, infection, emphysema/chronic obstructive pulmonary disease, stroke, and neuromuscular diseases which cause weakness.

Answer 414

Carotid body chemoreceptors are primarily responsive to reductions in arterial partial pressure of oxygen (PaO2). The carotid bodies are located at the bifurcation of the common carotid arteries bilaterally and contain afferent glossopharyngeal nerve branches that become stimulated in response to reductions in PaO2. Once the PaO2 falls below 60-65 mm Hg, neural activity increases to augment minute ventilation. Once the PaO2 increases to above 65 mm Hg, the neural input to the central respiratory centers ceases. Ventilation then falls again until the decrease in PaO2 surpasses this threshold again

Answer 415

The CAM-ICU screen is a quick screening tool which is used to assess for delirium. It uses acuteness or fluctuation in course along with inattention for the initial part of the screen. Additionally, the patient must have either an altered level of consciousness or disorganized thinking to test positive for delirium.

Answer 416

All volatile halogenated agents cause a dose-related relaxation of uterine smooth muscle. Nitrous oxide has no effect on uterine muscle tone.

Answer 417

PONV Strabismus surgery is associated with increased incidences of bradycardia and PONV. Succinylcholine should be avoided in patients undergoing strabismus surgery due to its effects on forced duction testing. Prophylactic ondansetron has been shown to be efficacious for the prevention of postoperative nausea and vomiting after strabismus surgery.

Answer 418

Aprepitant is a NK1 receptor antagonist. Aprepitant undergoes hepatic metabolism and has a half-life of about 10 hours. Aprepitant has very few side-effects and they are usually relatively mild. Aprepitant is associated with malaise, nausea, and rash as its most common side-effects.

Answer 419

Droperidol is an antidopaminergic medication that is often used to prevent or treat nausea and vomiting associated with anesthesia. Droperidol has been associated with dystonic reactions and extrapyramidal symptoms. Additionally, droperidol is associated with QT prolongation and has a FDA black box warning because of it. The QT prolongation of droperidol occurs in a dose dependent manner. Droperidol should be avoided in patients with long QT syndrome

Answer 420

Scopolamine is an antimuscarinic medication often used for motion sickness. Scopolamine can cross the blood brain barrier and acts centrally to prevent nausea. Scopolamine is often associated with dry mouth and blurred vision. Scopolamine is associated with delirium and delayed arousal in the elderly. Scopolamine can also be associated with other anticholinergic symptoms like urinary retention, tachycardia, and constipation

Answer 421

PRIS is associated with metabolic acidosis, rhabdomyolysis, congestive heart failure, and bradycardia. PRIS often occurs in the young and with high dose propofol infusions (>4mg/kg/hr). The pathophysiology of PRIS is related to an impairment of mitochondrial and fatty acid metabolism resulting in lactic acidosis and myocyte necrosis.

Answer 422

PION is more likely after spine surgery while AION is more likely after cardiac surgery.

Answer 423

Postoperative visual loss most often occurs due to optic nerve hypoperfusion or decreased oxygen delivery. ION following surgery generally presents with painless visual loss, visual field deficits, and sluggish pupils. Prognosis is poor and current treatment therapies are inadequate.

Answer 424

Glucagon is a polypeptide hormone secreted from the alpha cells of the pancreas that is known to cause decreased hepatic artery resistance and increased hepatic artery blood flow.

Answer 425

Acute respiratory acidosis is compensated by an increase in serum HCO3- of 2 mmol/L for every 10 mm Hg increase in PaCO2. Chronic respiratory acidosis is compensated by an increase in serum HCO3- of 4 mmol/L for every 10 mm Hg increase in PaCO2.

Answer 426

In cases of true allergy, aminoester local anesthetics (procaine, chloroprocaine, etc) are more likely to elicit allergic reactions compared to aminoamides (lidocaine, bupivacaine, ropivacaine, etc) because the aminoesters are derivatives of paraaminobenzoic acid (PABA), a known allergen (hapten to be precise).

Answer 427

Although allergic reactions to aminoamides are very rare, patients may occasionally react to preservatives such as methylparaben contained in the aminoamide formulation. Multiple-dose vials of lidocaine typically contain 0.1% of methylparaben added as preservative, whereas single dose solutions are typically methylparaben free. Methylparaben is the methyl ester of para-hydroxybenzoic acid, which is structurally similar to para-aminobenzoic acid (PABA), differing only in having a hydroxyl group vs amino group in the para position. Thus, cross-sensitivity between these compounds can occur.

Answer 428

Anatomic landmarks for the infra-gluteal sciatic nerve block include the greater trochanter of the femur, ischial tuberosity, and the sciatic groove.

Answer 429

Increased minute ventilation in pregnancy causes a respiratory alkalosis as PaCO2 falls to approximately 30 mmHg. An incomplete compensatory metabolic acidosis (bicarbonate falls to 20-21 mEq/L) means pH will rise slightly (around 7.44). Increased alveolar ventilation also leads to an increase in PaO2 (to 105-107 mmHg) early in pregnancy although this will slowly decline back towards normal as pregnancy progresses.

Answer 430

neuropathic

Answer 431

intubate...One of the first signs of a total spinal anesthetic in a neonate is apnea or respiratory depression which will likely necessitate intubation for controlled ventilation...Unlike adults who first present with subjective symptoms and cardiovascular signs, total spinal anesthesia in neonates presents with respiratory depression, which is typically seen as a decrease in oxygen saturation and apnea. Treatment is supportive and usually only involves intubation for controlled ventilation (C) until adequate spontaneous ventilation returns. However, failure to ensure adequate oxygenation can lead to hypoxic cardiac arres

Answer 432

Glycine toxicity causes hyperammonemia, which manifests as CNS symptoms and nausea. Transient blindness can also occur.

Answer 433

bladder perforation The main sign of bladder perforation is abdominal pain, the location of which will depend on the location of the perforation. Extraperitoneal perforation (the most common) causes periumbilical, inguinal or suprapubic pain, whereas intraperitoneal perforation causes diffuse or upper abdominal pain, or referred pain to chest and shoulders. Pain, of course, can only be reported by patients undergoing the procedure under spinal anesthesia that are conscious or lightly sedated. Also the spinal should preferably not have a level above T10 so that the pain of bladder perforation is not masked. Other signs may include pallor, sweating, abdominal rigidity, nausea, vomiting, hypotension, and tachycardia related to absorption of irrigating fluid. The other sign of bladder perforation is under the surgeon's purview, namely irregular return of irrigating fluid. Thus, communication is important if bladder perforation is suspected. Early detection and repair can prevent morbidity and mortality.

Answer 434

Metabolic Changes Associated With TPN: - Hypophosphatemia - Hyperglycemia - Hypercarbia - Hypokalemia - Hypomagnesemia - Hyperinsulinemia

Answer 435

TPN is most associated with hypercapnia, hyperglycemia, and hypophosphatemia. Additionally TPN can cause thrombophlebitis, hepatic steatosis, hypokalemia, hypomagnesemia, and hyperinsulinemia.

Answer 436

Unilateral epidural blocks can be caused by an epidural catheter that is located laterally in the epidural space, inadequate local anesthetic, or the presence of the plica mediana dorsalis.

Answer 437

Peritoneal dialysis is the preferred dialysis modality for patients who are intolerant of the hemodynamic changes induced by hemodialysis. This may include patients with a history of unstable angina, severe aortic stenosis, or heart failure with severely reduced ejection fraction.

Answer 438

An appropriate preoperative dose of oral midazolam is approximately 0.5 mg/kg in pediatric patients. The dose of oral midazolam is approximately 10 times the intravenous dose (0.05-0.1 mg/kg). This increase in dose is required due to decreased drug bioavailability (26-52%). The onset of action of oral midazolam is generally 15-30 minutes. By comparison, the onset of intravenous midazolam is typically less than 2-5 minutes.

Answer 439

The maximum recommended dose of lidocaine that may be injected during tumescent liposuction is 55 mg/kg. It is important to inform patients of the potential signs and symptoms of local anesthetic toxicity as peak plasma lidocaine concentrations occur 14-16 hours after initial injection for tumescent liposuction. If performed in an outpatient setting, the patient will most likely be at home during this window

Answer 440

Two days of smoking cessation can result in decreased carboxyhemoglobin which then shifts the oxyhemoglobin dissociation curve to the right (B) and results in increased oxygen availability. Smoking increases airway irritability and secretions, decreases mucociliary transport function, and decreases FVC and FEF25-75%, all leading to an increased incidence of postoperative pulmonary complications. Smoking cessation for longer than 4-6 weeks prior to surgery is associated with a decreased incidence of postoperative pulmonary complications, however, smaller benefits can be realized with smoking cessation of at least 48 hours prior to surgery.

Answer 441

Klippel-Feil syndrome is a congenital condition most often associated with fusion of the cervical spine. Patients with Klippel-Feil are often difficult to intubate because of the fusion and decreased neck mobility. Patients with Klippel-Feil are often described as having a short neck with a low hairline. Additionally, most may have associated scoliosis, strabismus, or scapular defects. Heart and other spinal conditions are more likely to occur in these patients as well.

Answer 442

Vomiting and Diarrhea come out of opposite ends. Vomiting goes up, and so does the pH (metabolic alkalosis). Diarrhea goes down, and so does the pH (metabolic acidosis). Vomiting = alkalosis. Diarrhea = acidosis.

Answer 443

Diarrhea causes a non-gap hyperchloremic metabolic acidosis and hypokalemia. Rarely it can lead to metabolic alkalosis. For metabolic acidosis, use the Winter formula to predict the compensatory change in PaCO2. Expected PaCO2 = (1.5 * [HCO3]) + 8 +/- 2. If the PaCO2 is significantly different then expected, suspect a mixed disorder.

Answer 444

A CT angiogram of the head should be ordered to screen for intracranial aneurysms. Patients with adult polycystic kidney disease (PKD) or autosomal dominant PKD (ADPKD) may have associated intracranial saccular or berry aneurysms, which are a contraindication to robotic assisted radical prostatectomy (RARP). Computed tomography with angiography of the head to delineate cerebral vasculature and the circle of Willis is therefore warranted before proceeding with surgery.

Answer 445

The steep head down position reduces lower extremity perfusion, increases central blood volume, and reduces cardiac output. Respiratory effects include decreased lung compliance, reduced functional residual capacity, and reduced vital capacity. A profound ventilation-perfusion mismatch may occur. The most significant effect of steep Trendelenburg position is increased intracranial and intraocular pressures. The prolonged Trendelenburg position is therefore relatively contraindicated in patients with cerebral aneurysms. Patients at risk for intracranial saccular aneurysms include those with ADPKD, Marfan syndrome, and Ehlers-Danlos syndrome. These coexisting diseases increase the risk of having vascular aneurysms throughout the body (e.g., circle of Willis, renal artery, aorta, etc.). Preoperative evaluation should therefore include cerebrovascular imaging such CT angiogram of the head to delineate the presence and size of any intracranial aneurysms.

Answer 446

Volatile agents have two opposing effects on cerebral blood flow: 1) They tend to decrease CBF by decreasing CMRO2 (this effect predominates at 0.5-1.0 MAC). Volatile agents, like every other anesthetic with the exception of ketamine and nitrous oxide, cause a decrease in CMRO2. Decreased CMRO2 causes a decrease in CBF, a mechanism known as flow-metabolism coupling. 2) They tend to increase CBF by causing cerebral vasodilation (this effect predominates at 1.5-2.0 MAC). In the past, this effect was incorrectly described as "uncoupling" when coupling is actually preserved (although shifted to a higher CBF for any given CMRO2, when compared to TIVA). Significant increases in CBF (accompanied by slight increases in CBV) are only seen with high concentrations of the modern volatiles.

Answer 447

Hyperglycemia is a common side effect of TPN, especially when it is started during severe stress, such as during sepsis. Since glucose utilization is still high, it is preferable to start insulin infusions to decrease the glucose levels rather than reduce the TPN glucose concentration. Thus, many of these patients may present for procedures with TPN and insulin infusions. While enteral nutrition should be held in accordance with fasting guidelines, TPN does not need to be held for most surgeries. If TPN must be stopped, the insulin infusion must be stopped also, and intravenous glucose infusions should be started, with frequent blood glucose monitoring for hypoglycemia. The incidence of hypoglycemia after TPN discontinuation can be reduced by using TPN solutions with a lower glucose to lipid ratio such as from 70:30 to 50:50.

Answer 448

During an AH episode, the intense sympathetic response below the level of SCI can cause acute hypertension (≥ 20-40 mm Hg above baseline), reflex bradycardia, cardiac arrhythmias, and myocardial infarction. The hypertension can further lead to headaches, blurred vision, retinal or intracranial hemorrhage, stroke, seizure, and/or cerebral edema. Additionally, the intense vasoconstriction leads to cool, dry, pale skin of the lower extremities. The reflex cutaneous vasodilation above the level of the SCI leads to nasal congestion; diaphoresis; and warm, flushed skin on the upper extremities, shoulders, neck, and face.] Spinal cord reflexes from the above stimuli trigger sympathetic activity (preganglionic sympathetic nerves) along the splanchnic outflow tract, but because of the SCI, inhibitory impulses from higher CNS centers (e.g. cerebral cortex, cerebellum, and brain stem) cannot reach below the level of SCI. Accordingly, intense generalized vasoconstriction occurs below the level of SCI while reflex cutaneous vasodilation occurs above the level of SCI (usually in proportion to the magnitude of the inciting stimulation).

Answer 449

Prevention of AH during surgery is best done with spinal or epidural anesthesia with a local anesthetic and/or deep general anesthesia. Narcotic-only regional anesthesia and sedation techniques do not reliably prevent AH. Treatment includes cessation of the triggering event and administration of direct vasodilators such as sodium nitroprusside, nitroglycerin, or nicardipine. Beta-blockers should be used cautiously as they can worsen reflexive bradycardia and if given in the setting of unopposed α-stimulation, may lead to severe vasoconstriction, hypertensive crisis, and congestive heart failure.

Answer 450

``` Low Characteristics Increased transfer Decreased transfer Size (molecular weight) < 500 Daltons Charge Uncharged Charged Lipid solubility Lipophilic Hydrophilic Ionization Unionized Ionized Protein binding Low (albumin) High (α-1-acid glycoprotein) Free drug fraction High Low ```

Answer 451

Placement of a left-sided central line is associated with increased complications. There is an increased incidence of arterial puncture because the left internal jugular vein is often smaller and overlays the internal carotid artery more often than the right. Additionally, the more tortuous course increases the incidence of malposition.

Answer 452

Although uncommon, carotid artery cannulation can lead to embolization. Carotid embolization on the left poses a greater risk as the left cerebral hemisphere is dominant in the majority of the population. This is also one of the reasons why right-sided carotid massage is preferred over left-sided massage. Another reason is that some investigations have found a greater cardioinhibitory effect on the right side.

Answer 453

The treatment of PHN includes anticonvulsants, tricyclic antidepressants, lidocaine patches, topical capsaicin, opiates, and tramadol.

Answer 454

Spinal cord stimulation is based on the “Gate Control Theory” of pain. Stimulation of large nerve fibers within the substantia gelatinosa may increase the inhibitory neurotransmitter γ-aminobutyric acid (GABA), and decrease the excitatory neurotransmitters (glutamate, aspartate).

Answer 455

Myasthenia gravis is a chronic disorder characterized by muscle weakness of skeletal muscles. Worsening muscle fatigue with muscle use is pathognomonic for MG. MG is an autoimmune disorder involving non-activating antibodies that bind to post synaptic acetylcholine (Ach) receptors at the neuromuscular junction. This leads to a decrease in the total number of functioning receptors. As many as 90% of patients are antibody positive. Between 15-60% of patients with MG have a thymoma or thymic hyperplasia.

Answer 456

Patients with MG are inherently resistant to succinylcholine. The ED95 of succinylcholine in MG patients is ~2.5 times that in non-myasthenic patients. A dose of 1.5-2.0 mg/kg should be adequate for most myasthenics, for rapid sequence intubation. It is probable that the requirements are increased due to the loss of receptors, because succinylcholine creates neuromuscular block by agonist action. Conversely, patients with MG are particularly sensitive to nondepolarizing neuromuscular blockade due to already having some Ach receptors blocked by MG antibodies. Additionally, nAChR downregulation is seen in myasthenia gravis, anticholinesterase poisoning, and organophosphate poisoning. Volatile anesthetics may synergistically promote neuromuscular blockade and delay emergence if administered in typical doses that would be given to a patient without MG.

Answer 457

Criteria that may predict the need for postoperative mechanical ventilation include: 1. Duration of disease 6+ years 2. Presence of pulmonary disease(s) unrelated to MG (e.g., COPD) 3. Vital capacity of < 2.9 L (or < 40 mL/kg) 4. Negative inspiratory force (NIF) < 20 cm H2O (e.g. 10 cm H2O) 5. Daily pyridostigmine dose > 750 mg

Answer 458

Myasthenic syndrome Myasthenia Gravis Clinical Proximal limb weakness (legs > arms), exercise improves strength, muscle pain common, reflexes are absent or decreased Extraocular, bulbar, and facial muscle weakness, fatigue with exercise, muscle pain is uncommon, reflexes are typically normal Gender Male > Female Female > Male Co-existing disease Small cell lung cancer Thymoma Response to relaxants Sensitive to succinylcholine Sensitive to nondepolarizing NMB Poor response to anticholinesterases Resistant to succinylcholine Sensitive to nondepolarizing NMB Good response to anticholinesterases

Answer 459

Preoperative creatinine greater than 1.2mg/dL, combined valve and bypass procedures, emergency surgery, and preoperative intraaortic balloon pump are risk factors most strongly correlated with post-cardiopulmonary bypass acute kidney injury. Other well-known minor risk factors include: female gender, congestive heart failure, chronic obstructive pulmonary disease, insulin-requiring diabetes, and depressed left ventricular ejection fraction.

Answer 460

Sevoflurane undergoes the most extensive metabolism (5-8%) followed by isoflurane (0.2%) then desflurane (< 0.2%).

Answer 461

Complications from celiac plexus blockade include (but are not limited to): orthostatic hypotension, diarrhea, retroperitoneal hemorrhage, hematuria, venous and arterial injection, aortic dissection, dysesthesia, interscapular back pain, backache, reactive pleurisy, hiccups, loss of bladder function, transient motor paralysis, and paraplegia.

Answer 462

Complex regional pain syndrome is separated into types I and II according to the inciting event. Type I (formerly known as reflex sympathetic dystrophy or RSD) is usually caused by a trivial injury, sprain, crush injury, or burn. Type II (formerly known as causalgia) is caused by a traumatic injury to a MAJOR NERVE trunk such as significant orthopedic trauma, gunshot injuries, or knife wounds. With either diagnosis, patients may develop burning pain and allodynia (pain to non-noxious stimuli). Both syndromes are also characterized by autonomic dysfunction, which presents with localized temperature changes, cyanosis, and/or edema. If the disease progresses without treatment, the skin can become glossy, smooth, and hairless

Answer 463

failure to ejaculate For an affected upper extremity, a stellate ganglion block may be performed, which may result in symptoms of Horner syndrome (ptosis, miosis, anhidrosis). For the lower extremity, a lumbar plexus block may be performed. Vasodilation and temperature change within 5-10 minutes of either block indicates a successful block.

Answer 464

Absolute indications for the use of a double lumen endotracheal tube outside of the operating room include the need for lung isolation to prevent contamination of a healthy lung such as in the case of massive pulmonary hemorrhage or unilateral lung abscess, the need for one-lung ventilation as in the case of a bronchopleural fistula or a traumatic bronchial disruption, as well as the need for regular lung lavage as in treatment of pulmonary alveolar proteinosis.

Answer 465

Codeine is an opiate prodrug whose effects are primarily dependent on metabolism to morphine, which requires the cytochrome P450 enzyme CYP2D6.

Answer 466

``` Sympathetic Block Indications: Vascular - Arterial/venous occlusion - Intra-arterial injection of irritants - Raynaud syndrome - Thromboangiitis obliterans - Vasospasm - Venous insufficiency Neuropathic - Acute herpes zoster - Complex regional pain syndrome I and II - Phantom limb pain Visceral - Abdominal cancers - Chronic pancreatitis - Refractory angina/acute myocardial infarction if medically indicated ```

Answer 467

Stellate ganglion: Located between C6-7. This ganglion can be blocked for pain (vascular, neuropathic, or visceral) that is related to the upper extremities and thorax. Complications include Horner syndrome, tracheal/esophageal injury, pneumothorax, and recurrent laryngeal nerve injury.

Answer 468

Celiac plexus: Located beside the aorta and inferior vena cava at the level of L1. The block is frequently done with a posterior approach with the entry point just below the 12th rib. This block is done for pain relating to abdominal cancers. Complications include bleeding, retroperitoneal hematoma, chylothorax, perforation of nearby structures, and pneumothorax.

Answer 469

Lumbar sympathetic chain: Located anterior to L1-L5 and the block is done via a posterior approach. This block may benefit those with neuropathic pain in the lower limbs, phantom limb pain of the lower extremities, and visceral pain involving the intestinal/urinary system. Complications involve perforation of nearby structures, genitofemoral nerve injury, and bleeding.

Answer 470

Cardiogenic pulmonary edema occurs due to left ventricular failure, mitral stenosis, or left atrial obstruction. This patient developed cardiogenic pulmonary edema after myocardial infarction. Increased hydrostatic pressures in the pulmonary vasculature lead to interstitial edema followed by increased alveolar fluid. Alveolar flooding occurs more in the dependent areas of the lung, which causes intrapulmonary shunting. This results in hypoxemia, hyperventilation, and hypocapnia, which can manifest in acute respiratory failure.

Answer 471

Cardiogenic pulmonary edema is most appropriately treated by supplemental oxygen, diuresis (especially loop diuretics), vasodilators, inotropes, and positive end-expiratory pressure (PEEP).

Answer 472

The determinants of myocardial oxygen demand are: 1) Heart rate 2) Contractility 3) Ventricle wall tension 4) Basal oxygen consumption

Answer 473

The cardioselective beta blockers include esmolol, atenolol, and metoprolol, which reduce chronotropy (heart rate), dromotropy (AV node conduction), and inotropy (contractility) to decrease myocardial oxygen demand and increase supply (more time in diastole). A mnemonic to recall the beta-1 selective beta-blockers is "BEAM" (β1, bisoprolol, betaxolol, esmolol, atenolol, acebutolol, metoprolol).

Answer 474

Type I hepatorenal syndrome is an acute renal failure caused by an inciting event in patients with liver cirrhosis. Mortality is high in these patients in the acute setting without treatment. Unlike type II, in type I hepatorenal syndrome the renal failure improves with treatment and stabilizes. Vasoconstrictors and volume expanders are the mainstay of treatment. Liver transplantation is the definitive treatment for type I and type II hepatorenal syndrome.

Answer 475

Hypoxemia is caused by five categories of etiologies: hypoventilation, ventilation/perfusion mismatch, right-to-left shunt, diffusion impairment, and low PO2. Low PO2 and hypoventilation are associated with a normal A-a gradient whereas the other categories are associated with an increased A-a gradient.

Answer 476

Ventilation/perfusion mismatch is the most common cause of hypoxemia. Normally, ventilation and blood flow are well matched. However, multiple disease processes can alter this relationship such as atelectasis, bronchospasm, COPD, airway obstruction, and pneumonia. As V/Q mismatch increases (worsens), the A-a gradient will also increase. A decreased V/Q ratio will respond to increased FiO2.

Answer 477

Shunts may be pulmonary (e.g. severe pneumonia, ARDS, lobar collapse, impaired hypoxic pulmonary vasoconstriction), extrapulmonary (e.g. atrial septal defect, ventricular septal defect, persistent ductus arteriosus), hepatopulmonary, or physiologic (e.g. bronchial and Thebesian venous drainage). A right-to-left shunt is always associated with an increased A-a gradient. Unlike other causes of hypoxemia, administration of oxygen to a patient with a true shunt does not significantly increase PaO2.

Answer 478

A-a gradient = PAO2 – PaO2 PAO2 = FiO2(Patm – PH2O) – (1.25 * PaCO2) Note: At standard Patm (760 mm Hg) and if humidity is assumed to be 100% in the alveoli, PH2O = 47 mm Hg. PaCO2 is also assumed to be equal to PACO2, so the latter can be used instead. This is a simplified formula derived from the alveolar gas equation.

Answer 479

Spinal cord stimulators activate the larger Aα and Aβ fibers to a greater degree than the smaller nociceptive Aδ and C fibers. This closes the “gate” in and impedes conduction of pain sensation past the substantia gelatinosa of the dorsal horn of the spinal cord.

Answer 480

The Aα and Aβ sensory nerve fibers largely conduct innocuous stimuli, whereas nociceptive stimuli are mainly transmitted by smaller diameter, thinly myelinated, or unmyelinated Aδ and C fibers. In 1965, Melzack and Wall proposed the “gate theory” of pain. An abundance of small afferent activity allowed the transmission of nociception through the substantia gelatinosa of the dorsal horn in the spinal cord. A spinal cord stimulator provides electrical stimulation to larger fibers, which have a lower threshold for recruitment by external electrical stimulation, and thereby closes the “gate” of the dorsal column. The closed “gate” prohibits transmission of the smaller, slower conducting fibers associated with chronic pain sensation. In other words, by triggering larger, faster transmitting Aα (conduction velocity 80-120 m/s) and Aβ fibers (30-70 m/s) within the same distribution as the slower Aδ (5-25 m/s) and C fibers (0.6-2 m/s) that are transmitting pain, a spinal cord stimulator effectively closes the “gate” in the dorsal horn, thereby reducing nociception.

Answer 481

Preterm labor can be initially treated with a variety of agents including β-adrenergic agonists, calcium channel blockers, cyclooxygenase inhibitors (e.g., NSAIDs), and magnesium sulfate. E

Answer 482

Terbutaline and ritodrine are two β-agonists commonly used for their tocolytic effects. They exhibit both β1 and β2 receptor activity. Recall that β1 receptors are most prevalent in the heart and increase heart rate and contractility when stimulated. The β2 receptors are more widely distributed on smooth muscles in the uterus, blood vessels, bronchi, intestines, and bladder. They are also located on other tissue such as the pancreas, liver, and skeletal muscles. Stimulation of β2 receptors causes smooth muscle relaxation, resulting in uterine relaxation

Answer 483

Early-onset (48-72 hours) adult ventilator-associated pneumonia (VAP) is associated with methicillin-sensitive Staphylococcus aureus (MSSA), Haemophilus influenzae, Streptococcus pneumoniae (Pneumococcus), as well as Proteus, Klebsiella, and Enterobacter species. In general, these are antibiotic-sensitive flora that enter the lower respiratory tract upon endotracheal intubation. There is a negligible change in mortality when patients are diagnosed with early onset VAP.

Answer 484

Late-onset VAP is associated with a fairly high mortality rate and is caused by more virulent organisms such as methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Acinetobacter species.

Answer 485

ntravenous Anticholinergics Duration Onset Recommended Cholinesterase Inhibitor Atropine 15 - 30 min 1 min Edrophonium Glycopyrrolate 2 - 4 hr 2 - 3 min Neostigmine, Pyridostigmine Scopolamine 30 - 60 min Neostigmine, Pyridostigmine

Answer 486

Higher than normal concentrations of bivalent cations such as magnesium or manganese interfere with the influx of calcium through P-type calcium channels in motor neurons. Reduced calcium influx leads to decreased acetylcholine release, which results in muscle weakness. This mechanism explains the potentiation of neuromuscular blocking drugs by magnesium.

Answer 487

typically phenoxybenzamine

Answer 488

Pruritus is a side effect of opioids and is particularly prevalent with neuraxial opioids (60-80%). Nalbuphine is the drug of choice for the treatment of pruritus induced by neuraxial opioids. When given in small doses (3 mg) it does not reverse the analgesic effect of neuraxial morphine.

Answer 489

Clinical manifestations of myotonic dystrophy are a result of delayed skeletal muscle relaxation after voluntary contraction. Two subtypes exist. Myotonic dystrophy type 1 is more common and can be congenital, child-onset, or most typically, autosomal dominant with adult-onset. Type 2 is rarer than type 1 and is typically associated with milder symptoms.

Answer 490

Tetanus is caused by Clostridium tetani, which secretes a toxin that inhibits neurotransmitter release from inhibitory neurons in the CNS. When inhibitory neurons are blocked severe muscle contractions occur. Tetanus often affects people who let their booster vaccinations lapse. Treatment for tetanus includes supportive care and administration of tetanus immunoglobulin

Answer 491

Botulism is caused by inhibition of neurotransmitter (acetylcholine) release from nerves at the neuromuscular junction, specifically the alpha motor neurons. Clostridium botulinum is the causative organism for botulism. Botulism causes a flaccid paralysis, often with cranial nerve involvement

Answer 492

Tetanus acts by preventing neurotransmitter release (glycine and GABA) from inhibitory neurons in the spinal cord. The lack of inhibition causes increased muscle contractions to the point of tetanus. Botulism toxin has a similar mechanism of preventing neurotransmitter release (acetylcholine), but botulism affects the alpha motor neuron causing flaccid paralysis.

Answer 493

Diarrhea and orthostatic hypotension are common complications of the celiac plexus block.

Answer 494

Ketamine is unique when compared to many other intravenous anesthetics: airway reflexes and respiratory drive are relatively preserved, significant analgesia is produced, and sympathetic tone is increased. Ketamine's analgesic effect is present even with relatively small doses.

Answer 495

Hyperkalemic periodic paralysis is a hereditary skeletal muscle ion channelopathy and often presents with muscle weakness, sometimes limited to the tongue and eyelids. It is thought to occur due to a defect in the sodium channel.

Answer 496

Precipitating factors include rest after strenuous exercise, potassium infusions, hypoglycemia, metabolic acidosis, or hypothermia. During the time of an attack, muscle weakness usually accompanies hyperkalemia with potential for dysrhythmias and subsequent respiratory failure. Treatment includes potassium restriction and thiazide diuretics. Glucose and insulin may also be given to cause an intracellular shift of potassium, which would decrease symptoms without losing total body potassium.

Answer 497

In contrast, hypokalemic periodic paralysis is caused by a calcium channel defect. It is precipitated by high glucose meals, strenuous exercise, glucose-insulin infusions, stress, and hypothermia. Note that opposing factors trigger these disorders, with the exception of hypothermia in both disorders. Paralysis spares the diaphragm but usually affects the limbs and the trunk

Answer 498

Labor is divided into three stages: - Stage I is the onset of true labor (regular contractions) until the cervix is completely dilated. - Stage II occurs once fully dilated until the baby is delivered. - Stage III starts after delivery of the baby and ends with delivery of the placenta.

Answer 499

The obturator nerve is a combined sensory and motor nerve which, in addition to providing cutaneous sensation to the medial thigh and a small area behind the knee, provides the majority of motor function to the adductor muscles. Blocking the obturator nerve severely decreases adduction strength.

Answer 500

No Several trials including the SAFE and ALBIOS studies have demonstrated that resuscitation with albumin versus resuscitation with saline have no differences in hospital or 90 day mortality. Some of the subgroup analyses from these trails suggest that trauma patients do better with crystalloid resuscitation, and patients with sepsis do better with albumin resuscitation. These subgroup analyses are small and not necessarily statistically significant, but may be suggestive of correlation.

Answer 501

In a patient with suspected cyanide toxicity, the first line treatment is hydroxocobalamin. Cyanide is a rapidly acting poison that can be produced by the combustion of synthetic materials. Cyanide toxicity is frequently seen in patients who have had smoke inhalation from residential or industrial fires. Smoke inhalation during a residential or industrial fire remains the leading cause of cyanide toxicity in the United States. Many providers now treat for potential cyanide poisoning in all patients who are being treated for carbon monoxide poisoning due to smoke exposure.

Answer 502

Cyanide causes its deleterious effects by inactivating cytochrome oxidase, which in turn causes an uncoupling of mitochondrial oxidative phosphorylation and an inhibition of cellular respiration. With aerobic respiration inhibited, cellular metabolism switches from aerobic to anaerobic and causes the production of lactic acid; this results in a metabolic acidosis.

Answer 503

Cyanide toxicity should be on the differential for any patient who presents with a history of smoke exposure or burns secondary to residential or industrial fire. In rare instances, patients with prolonged IV exposure to sodium nitroprusside can exhibit cyanide toxicity.

Answer 504

Epiglottitis is a severe bacterial infection of the supraglottic structures, which can include the epiglottis, arytenoids, and aryepiglottic folds. The disease most often occurs in children without Haemophilus influenza type B immunization, but can also occur secondary to Group A beta-hemolytic streptococcus as well as in adult patients (although this is rare). These patients can present in a sitting or "tripod" position with a sore throat, dysphagia, dyspnea, fever, and a muffled voice without cough. Epiglottitis can lead to decompensatory respiratory failure within hours if not treated quickly and deliberately.

Answer 505

The patient should receive inhalational induction in the sitting position to maintain spontaneous ventilation and avoid the risk of airway obstruction, which would occur with intravenous induction and neuromuscular blockade. Sevoflurane is the preferred volatile induction agent due to its bronchodilatory properties whereas desflurane is a bronchial irritant that may lead to laryngospasm. Nitrous oxide is typically avoided because it reduces the amount of oxygen available. Additionally, if a foreign body were suspected then nitrous oxide could lead to a ball-valve phenomenon and risk overinflation of a lung (e.g. pneumothorax).

Answer 506

A pudendal block targets the pudendal nerve, which originates at S2-S4. This nerve innervates the clitoris, perineal muscles, labial skin, vestibule, external anal sphincter, and perianal skin. This block can help treat the second stage of labor, but will not provide adequate analgesia during the first stage.

Answer 507

Myotonia congenita is a chloride channel skeletal muscle channelopathy and is characterized by a "warm-up effect" where muscle stiffness is normally worse after rest and improves with use. It is inherited in either an autosomal dominant or recessive pattern. Muscles of the hands and arms are preferentially affected in this disorder, and attacks are brought on by periods of stress, dehydration, and fatigue. Sympathetic activation is a major precipitating factor for myotonic events in patients with this disease, and perioperative pain management is crucial in the anesthetic management of these patients.

Answer 508

The alveolar gas equation is used to determine alveolar oxygen tension. PAO2 = [(Patm – PH2O) * FiO2] – (PACO2 / R). Increases in Patm and FiO2 and decreases in PH2O and PACO2 lead to increases in PAO2.

Answer 509

Negative pressure pulmonary edema has an incidence of 0.05-0.1% in all general anesthetics. Risk increases to 4% if airway obstruction occurs in a spontaneously breathing patient. Other risks include young age, male gender, physical fitness, and HEENT surgery.

Answer 510

Symptoms of negative pressure pulmonary edema include hypoxia, pink frothy fluid, and bilateral patchy infiltrates on CXR. Treatment of negative pressure pulmonary edema is supportive, with positive pressure ventilation either by endotracheal tube or CPAP.

Answer 511

Negative pressure pulmonary edema can occur following upper airway obstruction in a spontaneously breathing patient. When the patient attempts to inhale against a closed airway (laryngospasm, upper airway obstruction, blocked endotracheal tube) a significant negative intrathoracic pressure can develop. This negative force can be upwards of -50 to -100 cm H2O of pressure. The negative pressure causes a significant increase in preload, thereby increasing pulmonary blood volume. There is also a significant increase in left ventricular afterload, which causes a decreased cardiac output. The increase in pulmonary blood volume along with a decrease in cardiac output will increase the pulmonary transudative pressures. With all this occurring, pulmonary vascular resistance increases causing a shift of the intraventricular septum. The ventricular septal shift to the left causes a left ventricular diastolic dysfunction, which further increases pulmonary hydrostatic pressures.

Answer 512

Patients with SIADH will have hyponatremia, increased urinary sodium, and an increased urine osmolarity with decreased serum osmolarity. TrueLearn Insight : Hyponatremia may be common after a subarachnoid hemorrhage (SAH). The cause may be attributed to SIADH or cerebral salt wasting (CSW). Cerebral salt-wasting is diagnosed by marked decrease in serum sodium levels and intravascular volume. Treatment for CSW includes volume expansion and sodium administration. A mnemonic to help remember SIADH is syndrome of INAPPropriate anti-diuretic hormone for Increased Na (sodium) in PP (urine).

Answer 513

Characteristics of variable deceleration: 1) Visually apparent abrupt decrease in FHR occurs 2) Abrupt FHR decrease is defined as from the onset of the deceleration to the beginning of the FHR nadir of less than 30 seconds 3) The decrease in FHR of 15 bpm or greater occurs, lasting 15 seconds or longer and less than 2 minutes in duration 4) When the variable decelerations are associated with uterine contractions, their onset, depth, and duration commonly vary with successive uterine contractions

Answer 514

Following a parathyroidectomy, there is a redistribution of calcium and magnesium leading to hypocalcemia, hypomagnesemia, or both. Signs and symptoms of hypocalcemia include distal paresthesias, tetany, and in severe cases laryngospasm and seizures. Patients should be closely monitored for hypocalcemia and repletion should be immediately given if hypocalcemia is evident. The provider should have a high level of suspicion for hypocalcemia following a parathyroidectomy with plans for immediate treatment.

Answer 515

The classic laboratory findings in patients with pyloric stenosis who present several weeks into the disease course are hypokalemia, hyponatremia, and hypochloremic metabolic alkalosis with compensatory respiratory acidosis.

Answer 516

Pyloric stenosis

Answer 517

Pyloric stenosis can be a medical emergency, but is not a surgical emergency. Care should be taken to provide electrolyte and fluid resuscitation prior to surgical intervention. Balanced salt solutions should be initiated and potassium should not be added until adequate kidney function is assured.

Answer 518

Desflurane has been shown to be safe for use in renal failure patients. Hypotension, reduced cardiac output, pneumoperitoneum, and possibly sevoflurane are potentially hazardous to the kidneys.

Answer 519

Succinylcholine is associated with multiple side effects including, but not limited to: cardiovascular rhythm changes, hyperkalemia, muscle fasciculations, myalgias, and increases in intracranial pressure (ICP), intragastric pressure, and IOP.

Answer 520

Initial resuscitation in pediatric patients with severe dehydration begins with a 20 mL/kg bolus of an isotonic salt solution, usually 0.9% sodium chloride (B), Ringer’s lactate, or Plasmalyte. This clinical scenario may be common with pyloric stenosis.

Answer 521

Lusitropy is defined as myocardial relaxation. Positive lusitropy is illustrated on the myocardial pressure-volume loop as a reduction in the slope and a rightward shift of the diastolic filling phase (see black arrow on Figure 1 below). This change also leads to reduced left ventricular end-diastolic pressure (LVEDP’< LVEDP). Recall that coronary perfusion pressure (CPP) is the difference between aortic diastolic pressure (AoDP) and LVEDP. Positive lusitropy results in an increase in coronary perfusion pressure (CPP’ > CPP). Isovolumetric contraction occurs at a larger left ventricular end-diastolic volume (LVEDV’ > LVEDV) and the resulting stroke volume with improved myocardial relaxation (SV’) is greater than without improved relaxation (SV).

Answer 522

Inodilator therapy results in both an increase in lusitropy and an increase in inotropy. This effect can be seen with phosphodiesterase type 3 inhibitors, such as milrinone. This class of drug is also referred to as an inodilator due to the vasodilatory effects on vasculature in addition to the inotropy and lusitropy. This results in improved coronary perfusion pressure (CPP’), increased stroke volume (SV’) due to an increase in left ventricular end-diastolic volume (LVEDV’) and a decrease in left ventricular end-systolic volume (LVESV’), reduced aortic systolic pressure (AoSP’), as well as a positive inotropic effect (Contractility’)

Answer 523

Glycine is a neurotransmitter and amino acid which mediates the inhibition of central nociceptor terminals, thus reducing excitatory transmitter release (similarly to GABA and opioids).

Answer 524

Chemical stimuli that mediate the activation of peripheral nociceptors include prostaglandins, substance P, calcitonin gene-related peptide, glutamate, bradykinin, protons, ATP, and proinflammatory cytokines, whereas spinal cord inhibition is mediated by opioids, γ-aminobutyric acid (GABA), and/or glycine.

Answer 525

Although the risk of spinal hematoma with the antiplatelet drug clopidogrel (and ticlopidine) is unknown, ASRA recommends waiting seven days between discontinuing clopidogrel (14 days for ticlopidine) and performing a neuraxial anesthetic. A neuraxial anesthetic may be considered if clopidogrel is stopped for 5-6 days and platelet function is tested and found to be normal.

Answer 526

Garlic can inhibit platelet aggregation and increase fibrinolysis. Ginkgo can inhibit platelet activating factor. Ginseng can prolong PT and aPTT, and may inhibit platelet aggregation.

Answer 527

ASRA recommends stopping warfarin 4-5 days before a neuraxial anesthetic is attempted and checking that the INR has normalized. It is important to recognize that although INR may decrease within the first 1-3 days after stopping warfarin, the patient may still be at increased risk of spinal hematoma from a neuraxial anesthetic. This is because warfarin exerts its effects by interfering with the synthesis of coagulation factors II, VII, IX, and X. The decrease in INR primarily reflects a return of factor VII activity; however the patient is likely still coagulopathic since factor II and X levels have not yet normalized.

Answer 528

tends to make the body mroe alkaline

Answer 529

Hypothermia plays a major role in reducing cerebral metabolic demands during CPB. There is a natural “alkaline drift” with hypothermia owing to the increase in gas solubility and reduction of the PaCO2. The two methods of managing acid-base balance during CPB are noted as pH-stat and alpha-stat management. A pH-stat management technique corrects the alkaline drift by maintaining a neutral pH during hypothermia. Alpha-stat management allows the natural alkaline drift to occur without correction.

Answer 530

During pH-stat management, CO2 is added to the oxygenator or the CPB “sweep” may be reduced (the sweep mechanism removes CO2 from the CPB circuit). The addition of CO2 to the circuit increases total body CO2 in order to maintain pH neutrality despite the continuous reduction in core temperature. Advantages of pH-stat management include increased speed of homogenous cerebral cooling through cerebral vasodilatation, reduced cerebral metabolic rate of oxygen demand (CMRO2) while providing increased cerebral blood flow (CBF), and improved oxygen delivery to tissue by counteracting the leftward shift of the oxyhemoglobin curve typical of alkalosis. Disadvantages of pH-stat management include an increased delivery of embolic load to the brain as a result of the cerebral vasodilatation as well as loss of cerebral autoregulation. Outcome data support the use of pH-stat management during congenital heart surgery as a result of the homogeneous brain cooling.

Answer 531

Advantages of pH-stat management include increased speed of homogenous cerebral cooling through cerebral vasodilatation, reduced cerebral metabolic rate of oxygen demand (CMRO2) while providing increased cerebral blood flow (CBF), and improved oxygen delivery to tissue by counteracting the leftward shift of the oxyhemoglobin curve typical of alkalosis.

Answer 532

Disadvantages include increased delivery of embolic load to the brain and loss of cerebral autoregulation.

Answer 533

Alpha-stat management couples CBF with CMRO2. Autoregulation is maintained and the embolic load to the brain is minimized.

Answer 534

Transcranial Doppler (TCD) ultrasonography during CEA continually assesses mean blood flow velocity and detects microembolic events in the middle cerebral artery (MCA), thereby assisting in detection of intraoperative thromboembolic events. This modality is limited by the inability to detect global cerebral ischemia since it can only sense embolic events in the MCA.

Answer 535

Internal carotid artery stump pressures reflect the collateral flow back-pressure in the circle of Willis originating from the contralateral carotid artery. Stump pressures are inexpensive, dynamic, and are associated with detecting hypoperfusion at pressures < 50 mm Hg. They are not used to detect emboli.

Answer 536

Desflurane All volatile agents augment neuromuscular blockade by directly causing skeletal muscle relaxation and acting synergistically with NMBDs.

Answer 537

In HLHS, the left ventricle is significantly hypoplastic and essentially nonfunctional. Associated lesions include ASDs, severely stenotic or atretic mitral and aortic valves, patent ductus arteriosus (PDA), and a hypoplastic ascending aorta.

Answer 538

A rightward shift of hemoglobin P50 can occur within a day of smoking cessation (C). The P50 of hemoglobin is the partial pressure of oxygen in the blood at which the hemoglobin is 50% saturated with oxygen. The normal P50 of hemoglobin is approximately 27 mmHg.

Answer 539

A leftward shift increases hemoglobin's affinity for oxygen and reduces tissue delivery. The following factors cause a leftward shift of the P50 of hemoglobin: • Hypothermia • Carbon monoxide • Fetal hemoglobin (Hgb F) • Methemoglobin • Hypophosphatemia (seen in the critically ill)

Answer 540

A rightward shift decreases hemoglobin’s affinity for oxygen and increases oxygen delivery to tissues. The following factors cause a rightward shift of the P50 of hemoglobin: • Increased levels of 2,3 DPG (will occur when cigarette smoking is stopped) • Acidosis (also known as the Bohr effect) • Increased levels of carbon dioxide • Increased temperature

Answer 541

Smoking cessation shifts the P50 of hemoglobin to the right improving oxygen delivery to the tissues within 12-24 hours. Other effects of smoking cessation: • 48-72 hours: increased secretions and a more reactive airway • 2-4 weeks: decreased secretions and less reactive airway • 4-6 weeks: immune system and metabolism normalize • 8-12 weeks: improved mucociliary transport and small airway function

Answer 542

true Desflurane primarily decreases arterial pressure by decreasing afterload. Desflurane increases heart rate, particularly when the concentration is quickly increased, and also causes dose-dependent depression of myocardial function. Cardiac output is maintained and there is no significant effect on left ventricular diastolic function.

Answer 543

The renal cortex receives the lion’s share of the blood flow (~94%) but exhibits an oxygen extraction ratio of 18-20%. This leads to a relatively high PO2 within the renal cortex. The medulla, on the other hand, receives the remaining 6% of the renal blood flow but has an oxygen extraction ratio of nearly 80%. Because of this, a small change in total blood flow to the kidney could have exaggerated effects in the medulla causing local hypoxia and subsequent injury. The mechanisms of many perioperative renal insults are based on the disruption of adequate blood flow (and therefore oxygen delivery) to the renal medulla.

Answer 544

The mechanisms of many perioperative renal insults are based on the disruption of adequate blood flow (and therefore oxygen delivery) to the renal medulla. In this region, prostaglandins cause vasodilation, increasing blood flow. (NSAIDs) inhibit the synthesis of these compounds, preventing the increase of blood flow to the medulla. Similarly, in the kidney alpha receptors predominate over the beta, so endogenous epinephrine release due to pain or hypoperfusion has the effect of vasoconstriction, again decreasing blood flow to the medulla. Thus, phenomena that disrupt the delicate oxygen balance in the medullary thick ascending loop are often to blame for the subsequent kidney injury.

Answer 545

``` Age Group Blood Volume (mL/kg) Premature infant 90-105 Full term newborn 80-90 Infant (3 months - 1 year) 70-80 Child (1-12 years) 70-75 Adult Male 65-70 Adult Female 60-65 ```

Answer 546

Transpulmonary pressures are highest in patients with restrictive lung disease, such as idiopathic pulmonary fibrosis. Diseases that decreases the volume of air the lungs are able to hold are known as restrictive lung diseases. They are often a result of a decrease in the elasticity of the lungs themselves or caused by a problem with the expansion of the chest wall. Examples of restrictive lung diseases include asbestosis, sarcoidosis, and pulmonary fibrosis.

Answer 547

Patients who receive an excessive amount of acetylcholinesterase (AChE) inhibitor are at an increased risk of developing weakness. The recommended maximum dose of neostigmine is 0.07 mg/kg.

Answer 548

pKa is the dissociation constant that characterizes the equilibrium of weak acids and bases between their ionized and unionized forms. As the pH of a carrier solution increases, the ionized fraction of weak acids and the unionized fraction of weak bases will increase. As the pH falls, the opposite is true. In general, the higher the pH of a solution, the more of a weak base such as lidocaine will exist in its unionized fraction.

Answer 549

Muscle contraction occurs through a series of several steps. The presynaptic neuron first undergoes depolarization via an influx of sodium ions. Depolarization of the nerve triggers the influx of calcium into channels at the nerve terminal. Calcium facilitates the release of acetylcholine molecules out of the presynaptic nerve and into the neuromuscular junction. The acetylcholine molecules then bind to nicotinic acetylcholine receptors on the motor end plate, which leads to depolarization and then contraction of the muscle.

Answer 550

Blocking the motor end plate acetylcholine receptor does not allow the muscle to contract. Because rocuronium is a competitive antagonist, its action can be overcome (in other words rocuronium can be displaced) by large numbers of the receptor agonist. This is the mechanism of neostigmine, the "reversal" agent. It is important to note that the term "reversal" does not imply antidote or a permanent (non-competitive) reversal. Neostigmine is an acetylcholinesterase inhibitor. Acetylcholinesterase is the enzyme that degrades acetylcholine, and blocking this enzyme leads to increased numbers of acetylcholine molecules. The acetylcholine then displaces the rocuronium from the acetylcholine receptor, allowing muscle contraction.

Answer 551

Unlike neostigmine, the drug Sugammadex is a selective relaxant binding agent (SRBA). Sugammadex is a modified γ-cyclodextrin, with a lipophilic core and a hydrophilic periphery. The negatively charged extensions electrostatically bind to the quaternary nitrogen of rocuronium as well as contribute to the aqueous nature of the cyclodextrin. Sugammadex's binding encapsulation of rocuronium is one of the strongest among cyclodextrins and their guest molecules. The rocuronium molecule bound within Sugammadex's lipophilic core is rendered unavailable to bind to the acetylcholine receptor at the neuromuscular junction.

Answer 552

The ARDS Network demonstrated a 22% reduction in mortality when patients with ARDS were mechanically ventilated at tidal volumes using 6 mL/kg of PBW and plateau pressures ≤ 30 cm H2O. Plateau pressures are measured after the inspiratory pause during volume-cycled ventilation.

Answer 553

75% Train-of-four (TOF) is a commonly used method to monitor neuromuscular blockade. The gold standard, however, is the TOF ratio with adequate reversal at a ratio of 0.9. The number of twitches correlate to the degree of nAChR blockade (0 = 100%, 1 = 90%, 2 = 80 %, 3 = 70-80%, 4 = ≤ 65-70%).

Answer 554

increases tone

Answer 555

Metoclopramide is relatively contraindicated in patients with Parkinson's disease due to dopamine (D2)-receptor antagonism

Answer 556

Hypoparathyroidism with resultant hypocalcemia is a common complication of total thyroidectomies. Acute hypocalcemia generally presents at 24-48 after surgery. Stridor and airway obstruction are common presenting signs, making hypocalcemia the most common cause of airway obstruction when greater than 24 hours post-op.

Answer 557

The following findings on capnography are suggestive of (but not specific for) an incompetent inspiratory valve and should prompt the examination of the valve. 1) Elevated inspired carbon dioxide baseline, indicated by red markings in figure below. 2) Prolonged expiratory plateau, orange markings below. 3) Gradual (instead of sharp) inspiratory down stroke, orange markings below.

Answer 558

postiive pressure ventilation A neonate with persistent cyanosis and heart rate less than 100 beats per minute (bpm) requires positive pressure ventilation.

Answer 559

Atropine is a tertiary amine, which more easily crosses the placenta than does glycopyrrolate, a quaternary amine. Therefore atropine should be given in conjunction with neostigmine for reversal of pregnant patients to avoid fetal bradycardia.

Answer 560

CCr = (Urine creatinine * Urine volume) / Plasma creatinine

Answer 561

Fractional excretion of sodium (FENa) is used to determine the cause of an established acute kidney injury. It can identify whether acute kidney injury is caused by a prerenal, intrinsic, or postrenal etiology. Study results may become confounded with the use of diuretics. FENa = (Urine sodium * Plasma creatinine) / (Urine creatinine * Plasma sodium) FENa < 1% = Prerenal FENa > 1% = Intrinsic (e.g. acute tubular necrosis) FENa > 4% = Postrenal

Answer 562

he transverse process of C6 is the major landmark for stellate ganglion blockade. The stellate ganglion is the fusion of the inferior cervical and first thoracic sympathetic ganglia and first thoracic ganglia. It receives preganglionic sympathetic fibers from T1-T6. Stellate ganglion blocks are commonly used to diagnose and treat complex regional pain syndrome (CRPS) of the upper extremity. The location of the stellate ganglion is in the neck generally anterior to the C7 vertebral body. Directly superior to the ganglion is the transverse process of C6, which is referred to as the Chassaignac tubercle (or carotid tubercle). Because of its prominence and proximity to the stellate ganglion, the Chassaignac tubercle is often used as the landmark to perform the block.

Answer 563

The hallmark of SIADH is the combination of euvolemia, hypotonic plasma (due to increased free water retention from ADH), hypertonic urine (urine osmolality >100 mOsm/kg H2O), and high urine sodium (>20 mEq/L). Syndrome of INAPPropriate anti-diuretic hormone results in Increased NA (sodium) in the PP (urine).

Answer 564

Induced hypothermia following cardiac arrest can reduce ischemic injury and improve neurologic outcomes. It is accomplished by various cooling methods for a duration of 12-24 hours post-resuscitation with a goal temperature of 32 °C to 36 °C. Rewarming should occur slowly to avoid major complications. can given meperidine to decrease shivering and decrease metabolic demand

Answer 565

FENa: [(PCr x UNa ) / (PNa x UCr)] x 100.

Answer 566

Triggers for HKPP include potassium-rich meals or exogenous potassium administration, stress, rest after exercise, metabolic acidosis, and depolarizing muscle relaxants.

Answer 567

ECT requires minimum seizure duration of 25-30 seconds to ensure adequate antidepressant efficacy. Methohexital or etomidate are the best options depending on patient circumstances. Avoidance of etomidate in patients with baseline hypertension or CAD is advisable as it does not blunt the sympathetic surge associated with ECT. TrueLearn Insight : If patients are experiencing excessively long seizures (>100 seconds), propofol may be a useful alternative to methohexital.

Answer 568

caffeine, etomidate, aminophyline

Answer 569

thiopental, propofol lidocaine, midazolam, diltiazam, lorazepam

Answer 570

above the vertebrate, except for C8, which comes underneath C7 vert

Answer 571

Angiotensin II causes efferent glomerular arteriolar vasoconstriction which will maintain or increase glomerular filtration rate (GFR) in states of hypovolemia.

Answer 572

Renin is produced in the kidneys in response to decreased renal perfusion and cleaves angiotensinogen into angiotensin I. Angiotensin I is converted to angiotensin II by ACE in the lungs and kidneys. Angiotensin II then promotes aldosterone production. Angiotensin II and aldosterone both act to increase intravascular volume, raise systemic blood pressure, and maintain adequate GFR.

Answer 573

75% The spinal cord receives its blood supply from one anterior spinal artery providing about 75% of the blood supply, which supplies the motor tracts. The two posterior spinal arteries supply the sensory tracts.

Answer 574

Arterial pressure variation is an accurate method to determine volume status, with SVV > 13% suggesting fluid responsiveness.

Answer 575

The relationship of surface tension and size of the alveoli can be quantified with the LaPlace law: Pressure = 2 * T / r = (2 * surface tension) / radius

Answer 576

Pulmonary surfactant more effectively reduces surface tension when it is more concentrated. As alveoli shrink, the surfactant concentration increases which more effectively reduces surface tension. On the other hand, as alveoli become more distended, the surfactant is stretched more thinly which results in a decrease in concentration. Subsequently, the surface tension will increase and favor a reduction in size.

Answer 577

Metabolic alkalosis can be caused by blood product administration; gastric losses, urinary loses, or excessive exogenous bicarbonate administration.

Answer 578

metabolic alkalosis

Answer 579

Codeine is an inactive medication that becomes morphine after CYP 2D6 metabolism. There is a wide polymorphism in this metabolic pathway. Therefore, some people do not metabolize codeine into morphine (poor pain control) and others metabolize large amounts rapidly (morphine overdose). Several pediatric deaths have been attributed to codeine use in post tonsillectomy patients; likely these patients were rapid metabolizers. Inhibitors of CYP 2D6 include quinidine and serotonin specific reuptake inhibitors (SSRIs) such as fluoxetine. Therefore, codeine is not an ideal opioid for patients who are taking SSRIs.

Answer 580

The LFCN may be anesthetized by injecting local anesthetic 2-2.5 cm medial and 2-2.5 cm inferior to the ASIS and above and below the fascia lata.

Answer 581

The femoral nerve (L2-4) travels below the fascia iliaca, deep to the fascia lata. A femoral nerve block with greater than 20 ml of local anesthetic is typically adequate for anesthetizing the LFCN due to anesthetic spread between the fascia iliaca and the fascia lata. Meralgia paresthetica (MP) is entrapment of the LFCN, associated with burning pain over the distribution. Pregnant women often present with MP following prolonged labor. The LCFN may be impinged against the inguinal ligament while their legs are in stirrups.

Answer 582

The efferent branch of the laryngospasm reflex is mediated by the recurrent laryngeal nerve. The recurrent laryngeal nerve innervates all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscle. The lateral cricoarytenoid and transverse arytenoid muscles are major adductors of the vocal cords and responsible for laryngospasm.

Answer 583

The internal branch of the superior laryngeal nerve is responsible for sensory innervation of the trachea at and above the level of the vocal cords. This means that the internal branch of the superior laryngeal nerve functions as the afferent limb of the laryngospasm reflex.

Answer 584

Aspiration Management Steps: 1) The patient should be placed in the left lateral position to minimize the risk of further aspiration. The supine position may result in more aspiration where the left lateral position is theorized to help pool secretions in the oropharynx. Another option is the patient Trendelenburg position to help pool aspirate in the mouth, preventing it from going into the pulmonary tree with gravity. 2) Suctioning of the aspiration should be initiated. This is why all anesthetics should not occur until proper suctioning is confirmed. 3) Immediate tracheal intubation should occur. 4) If possible, avoidance of positive pressure ventilation until tracheal suctioning can occur. If the patient is hypoxic, ventilation may need to occur before suctioning to improve oxygenation. 5) Depending on patient and surgical circumstances, proceeding with the case may be warranted. If patient becomes hypoxic, abandoning the procedure may be necessary or alternative surgical intervention should be pursued. 6) Most patients can be extubated following aspiration but determining this will depend on many variables.

Answer 585

Severe abrupt hypoxia under one-lung ventilation requires a return to two-lung ventilation, at least temporarily. After confirming double-lumen tube position, assuring 100% O2 is being delivered, and maintaining normal cardiac output, the modern answer for hypoxemia under one-lung ventilation is to apply PEEP to the dependent lung, at least in patients without significant COPD. CPAP, on the other hand, is relatively contraindicated in video-assisted thoracoscopic surgery and would warrant a discussion with the surgeon before employing.

Answer 586

Glossopharyngeal nerve

Answer 587

The glossopharyngeal nerve is blocked at the palatoglossal folds. The recurrent laryngeal nerve can be blocked with a transtracheal injection through the cricothyroid membrane. The superior laryngeal nerve can be blocked by either injection at the horn of the hyoid bone or by placing a pledget in the pyriform sinus. The mandibular portion of the trigeminal nerve is blocked topically.

Answer 588

Septic shock results in a complex pathophysiologic process involving cytokine release, complement activation, endothelial activation, induction of TF expression, and depression of cell-mediated immunity. This process emphasizes the link between the inflammatory response and clotting cascade, both of which can result in organ hypoperfusion.

Answer 589

Most opioids are not particularly effective for neuropathic pain and may have unwanted side effects in the elderly population. However, methadone is often effective since in addition to opioid agonist properties, it is also an N-methyl-d-aspartate (NMDA) antagonist and serotonin reuptake inhibitor. Antiepileptics (such as gabapentin or carbamazepine), antidepressants (such as tricyclic antidepressants (TCAs), including desipramine and amitriptyline), and selective serotonin reuptake inhibitors (SSRIs) are used in combination for the treatment of diabetic neuropathy. Tramadol is considered particularly useful for the treatment of neuropathic pain because, in addition to its partial opioid receptor agonist properties, it also prevents the reuptake of norepinephrine and serotonin, which is thought to be beneficial for modulating neuropathic pain.

Answer 590

``` Causes of Nicotinic AChR Upregulation: - Nerve Injuries o Stroke o Spinal cord injury - Burns (24 hours up to 1-2 years after burn injury) - Prolonged immobility (risk greatest after 16 days) - Prolonged exposure to neuromuscular blockers - Myopathies o Duchenne muscular dystrophy - Denervation Disorders o Multiple sclerosis o Guillain-Barré syndrome o Amyotrophic lateral sclerosis ```

Answer 591

Inability to extend the neck and create a sternomental distance ≥ 12.5 cm is associated with difficult intubation.

Answer 592

Interincisor distance of less than 3 cm is a predictor of difficult intubation.

Answer 593

Thyromental distance less than 6.5 cm indicates a small mandible and may predict difficult intubation.

Answer 594

Nitrous oxide is poorly soluble in the blood and equilibrates quickly. Nitrous oxide causes an increase in cerebral metabolic rate, cerebral blood flow, and ICP. Nitrous oxide can also diffuse into air-filled cavities causing expansion of these areas (e.g. pneumothorax, pneumocephalus).

Answer 595

Intracranial pressure (ICP) is the pressure inside the skull and is normally between 5 and 15 mmHg. ICP is considered elevated when the pressure is greater than 20 mmHg.

Answer 596

Dexmedetomidine is an alpha-2 receptor agonist, which is used for sedation. Dexmedetomidine causes minimal respiratory depression. Dexmedetomidine is unique in that it produces a sleep-like state on EEG. ICP decreases and the cerebral perfusion pressure increases when dexmedetomidine is administered. Side-effects of dexmedetomidine include bradycardia and hypotension. Dexmedetomidine can also cause paradoxical hypertension when a bolus is administered as a result of alpha-2 agonism in the peripheral vasculature. Clonidine is another alpha-2 agonist but with less specificity than dexmedetomidine.

Answer 597

- Etomidate is an imidazole compound. - Etomidate is considered a hemodynamically stable induction agent, because is has minimal cardio depressant effects and minimal vasodilatory effects. - Etomidate causes pain on injection because of the acidic nature of the propylene glycol which it is dissolved in. - Etomidate decreases the cerebral metabolic rate, cerebral blood flow, and ICP, while maintaining cerebral perfusion pressure. - Additionally, etomidate inhibits 11-beta-hydroxylase and can cause adrenal suppression.

Answer 598

Methohexital is a barbiturate anesthetic agent. Methohexital can cause myoclonus and pain on injection. Methohexital does not significantly affect the seizure threshold but is often used for electroconvulsive therapy. Barbiturate anesthetics cause a decrease in cerebral metabolic rate, decreased cerebral blood flow, and therefore a decreased ICP.

Answer 599

Hypokalemic periodic paralysis is a rare autosomal dominant disorder resulting in an abnormal dihydropyridine sensitive calcium channel. Abnormal uptake of potassium by muscle cells is felt to contribute to severe hypokalemia and paralysis. Paralysis may be induced by a decrease in serum potassium levels. Factors known to trigger episodes are: stress, cold environment or hypothermia, carbohydrate load, infection, glucose infusion, metabolic alkalosis, alcohol, strenuous exercise, and steroids. These patients are especially vulnerable in the perioperative period with fasting, cold temperature, possible glucose infusions, possible steroid administration, and the stress of surgery/anesthesia. An increase in episodes has also been associated with pregnancy.

Answer 600

ALDOSTERONE

Answer 601

Conn syndrome is primary hyperaldosteronism. It results in elevated serum Na+, reduced serum K+, and reduced renin activity. Can lead to hypervolemia. Patients typically present with increased blood pressure, fatigue, and a hypokalemic metabolic alkalosis. Anesthetic management includes preoperative K+ repletion and volume management. Intraoperatively, hyperventilation should be avoided and cortisol may need to be administered if both adrenal glands are being excised.

Answer 602

Donepezil is a reversible, non-competitive inhibitor of acetylcholinesterase which can cause increased availability of acetylcholine at neuromuscular junctions. Patients on donepezil should be monitored for prolonged relaxation after succinylcholine. In Alzheimer patients, acetylcholine concentration is diminished and the effect of acetylcholine is reduced. Cholinesterase inhibitors (donepezil, galantamine, rivastigmine) are commonly prescribed because they block acetylcholinesterase and increase the availability of acetylcholine. Because of the increased presence of acetylcholine, patients on donepezil will have prolonged relaxation after succinylcholine and show increased resistance to nondepolarizing muscle relaxants. Some sources recommend that donepezil be held 2-3 weeks prior to surgery.

Answer 603

A full E-cylinder contains 660 L oxygen at 1900 or 2200 psig

Answer 604

Blue 1600 L 745 PSI

Answer 605

Gray 1600L 840 PSI

Answer 606

Brown 500L 1600 PSI

Answer 607

The cutaneous innervation of the medial arch of the foot is supplied by the saphenous nerve which is a branch of the femoral nerve. To perform a block of this nerve at the ankle, local anesthetic infiltration can be performed around the saphenous vein where it passes anterior to the medial malleolus.

Answer 608

Factors that improve the accuracy of cardiac output measurement by thermodilution include high injectate volume, low injectate temperature, and a high cardiac output. Factors that degrade the accuracy of this method of monitoring include low cardiac output, tricuspid regurgitation, and intra-cardiac shunting.

Answer 609

Barium hydroxide absorbent preparations produce more carbon monoxide than soda lime due to the decreased water content of barium hydroxide absorbents.

Answer 610

Barium hydroxide absorbents are the most likely to produce compound A and be associated with fire production with sevoflurane administration.

Answer 611

Carbon dioxide absorbents containing barium hydroxide produce the most compound A and have the highest risk for fire production during sevoflurane administration. Soda lime, due to higher water content, has a reduced incidence of compound A and fire production. Calcium hydroxide absorbents, due to lower reactivity, have the lowest incidence of compound A and fire production. Desiccated absorbents absorb less CO2, produce more heat and carbon monoxide, and have an increased risk of compound A and fire production.

Answer 612

Line isolation systems (isolation transformer + line isolation monitor) protect persons from electrocution by turning a normal “grounded system” (that exists outside the operating room) which only needs a single fault to cause electrocution into a “protected” system in which two faults are needed to deliver a shock. The line isolation monitor determines the degree of isolation between the two power wires and the ground and predicts how much current could flow if a second short-circuit were to develop. An alarm goes off if an unacceptable amount of current to the ground is possible (e.g. the "isolated" system is no longer isolated, but rather is grounded, thus only one additional fault could result in a shock)

Answer 613

When the line isolation monitor alarms, the first step should be to unplug the most recent electronic device that was plugged in.

Answer 614

The larynx is divided into three parts (supraglottis, glottis, and the subglottis). The action of the lateral cricoarytenoid muscles combined with that of the transverse arytenoid muscles results in adduction (closing) of the vocal folds. The posterior cricoarytenoid muscles are involved in abduction (opening) of the vocal folds. The principal tensors of the vocal folds are the cricothyroid muscles, which by their action elongate and tighten the vocal ligaments, raising the pitch of the voice. The principal relaxers are the thyroarytenoid muscles. Motor innervation to all muscles of the larynx is supplied by the recurrent laryngeal nerve except the cricothyroid muscle (tensor muscle of the larynx), which is supplied by the external branch of the superior laryngeal nerve.

Answer 615

Absolute contraindications which include pregnancy, bleeding disorders, and anticoagulation therapy. Relative contraindications include large aortic or renal aneurysms, untreated urinary tract infection (UTI), ureteral obstruction distal to the calculus, implanted pacemaker/defibrillator, and morbid obesity.

Answer 616

Placenta previa, prior uterine surgery, multiparity, advanced maternal age, and smoking are risk factors for placenta accreta.

Answer 617

The anterior wall of the left ventricle is most commonly perfused by the left anterior descending (LAD) artery. The circumflex perfuses the lateral wall (inferolateral, anterolateral).

Answer 618

Propofol is a short acting intravenous general anesthetic agent that works by agonism of the GABA receptor.

Answer 619

Give plateletts Maximal amplitude is a characteristic of the maximal clot strength during the clotting cascade. This process is highly dependent on both platelet number and function as well as fibrin cross-linking.

Answer 620

short on factors--give FFP

Answer 621

Cryoprecipitate would be most helpful in correcting abnormalities in K-time as well as alpha-angle which are measures of the speed and strength of clot formation. ...need fibrinogen....Cryoprecipitate contains factor VIII and fibrinogen.

Answer 622

The order of sensitivity, from lowest to greatest, for detection of VAE with the following modalities is ECG, ETCO2, PAC, precordial Doppler, and TEE

Answer 623

PEEP is a ventilation parameter that can provide positive airway pressure at the end of the respiratory cycle. Under normal conditions, there is a component of physiological PEEP that stents alveoli open, preventing atelectasis. Under general anesthesia, this can be lost and must be supplemented with mechanical PEEP. By preventing alveolar collapse, this will improve ventilation, oxygenation, and V/Q matching. The lung volume at the end of expiration is referred to as functional residual capacity (FRC). By increasing the number of patent alveoli, the total lung volume at the end of expiration in increased, thereby increasing FRC.

Answer 624

Most patients with primary hyperaldosteronism should be treated with spironolactone, a competitive aldosterone receptor antagonist and potassium-sparing diuretic. The drug takes several weeks to correct hypertension and hypokalemia. Accordingly, it is usually necessary to administer additional antihypertensives and to initially provide potassium supplementation since total body potassium stores may be very low. Helps in two ways: decreases HTN and helps retain some K+. Good job spirinolactone

Answer 625

Aldosterone is a mineralocorticoid produced in the adrenal glands. It is released following activation of the renin-angiotensin-aldosterone pathway in response to hypovolemia and renal hypoperfusion or in response to elevated serum potassium. Aldosterone primarily acts in the renal distal tubules and collecting ducts to upregulate Na+/K+ pumps. This promotes increased reabsorption of sodium (and water) and secretion of potassium into urine. Supraphysiologic aldosterone secretion therefore leads to hypertension and hypokalemia.

Answer 626

Octreotide is the primary pharmacologic treatment of acromegaly as it suppresses growth hormone production.

Answer 627

Organophosphates are used as insecticides worldwide, but in the U.S. have been most commonly used as agricultural pesticides. The agents act by irreversibly binding acetylcholinesterase and rendering it non-functional. This leads to an overabundance of acetylcholine molecules, which can then bind at all acetylcholine receptors including postganglionic parasympathetic receptors (muscarinic) and neuromuscular junction receptors (nicotinic). Signs and symptoms of acute toxicity are generally those associated with cholinergic crisis. These most commonly include bradycardia, miosis (small pupils), lacrimation, salivation, bronchorrhea, bronchospasm, urination, emesis, and diarrhea. In addition, nicotinic activity can cause fasciculations initially, followed by weakness and paralysis. Cholinergic activity in the CNS results in confusion and somnolence. Diagnosis is generally made by history and physical exam.

Answer 628

Treatment of organophosphate poisoning first consists of supportive measures. If patients have markedly depressed mental status or muscle weakness, 100% oxygen and tracheal intubation should be performed. Succinylcholine should be avoided, however, because it is degraded by pseudocholinesterase, which is also inhibited by organophosphates. If topical exposure is suspected, the patient’s clothes should be removed and the affected areas should be aggressively irrigated. Pharmacologic treatment consists of pralidoxime and atropine, although there is debate on the effectiveness of pralidoxime. Pralidoxime works by binding to the organophosphate molecules and reactivating acetylcholinesterase. By reactivating acetylcholinesterase, it is effective in treating both muscarinic and nicotinic symptoms. It generally only works if given within the first 48 hours of exposure. Atropine is a cholinergic antagonist at the muscarinic receptors, therefore preventing cholinergic parasympathetic activity. It is therefore most useful for drying pulmonary secretions and treating bradycardia.

Answer 629

Side effects from excessive cholinergic activity can be remembered with the mnemonic SLUDGE Mi ("SLUDGE ME"): Salivation, Lacrimation, Urination, Diaphoresis, GI upset, Emesis, Miosis.

Answer 630

inhaled agents with a high FA/FI value are associated with a low solubility while higher blood solubility values are associated with a lower FA/FI ratio

Answer 631

Agent MAC Value Blood:Gas Partition Coefficient Isoflurane 1.2 1.5 Sevoflurane 1.8 0.65 Desflurane 6.6 0.42

Answer 632

prothrombin time (or INR) is a better marker of liver synthetic function and can provide timely information because of the short life of factor VII (approx 4 hours). Furthermore, prothrombin time provides prognostic information as well (together with the serum bilirubin and creatinine levels, it is used to calculate the MELD score).

Answer 633

A--Complete cord injury with complete motor and sensory deficits in S4 and S5 nerve roots B--Incomplete cord injury with sensation preserved below the level of injury; intact S4 and S5 nerve roots C--Incomplete cord injury with motor function preserved below the level of injury; < 3 out of 5 motor strength in half of the major muscle groups D--Incomplete cord injury with motor function preserved below the level of injury; ≥3 out of 5 motor strength in half of the major muscle groups E--No evidence of cord injury with intact motor and sensory innervation

Answer 634

To avoid the windsock effect, hypotension, rapid ventricular pacing, or transient asystole can be employed. These maneuvers reduce the shear force exerted on the stent-graft during deployment.

Answer 635

Adenosine should be cautiously used in patients with asthma or upper respiratory disease because adenosine can cause bronchoconstriction.

Answer 636

Once the stent-graft is deployed, it cannot be repositioned. This makes the time of deployment very crucial. As the stent-graft begins to open, the ejection force of the heart can push the stent-graft, and cause it to migrate distally. This is referred to as the "windsock effect". This is especially a concern with thoracic aortic aneurysm stenting.

Answer 637

Elective repair of an aneurysm is indicated if the size is > 5.5 cm or the rate of growth is > 1.0 cm per year. In endovascular repair, access is gained through the femoral or iliac arteries. The appropriate stent-graft is advanced through the aorta to the target site. The position of the stent-graft can be monitored with aortography. Choosing the appropriate size for the stent-graft is essential, as oversizing can lead to folding, and undersizing can lead to migration or leaks around the stent-graft.

Answer 638

Potassium iodide is effective at reducing I-131 uptake by the thyroid and reduces the incidence of radiation exposure related thyroid complications.

Answer 639

The development of hypercarbia during laparoscopic and robotic surgery is common and can lead to tachycardia, bradycardia, hypertension, hypotension, myocardial depression, arrhythmias, and even cardiac arrest. Monitoring with end tidal carbon dioxide concentration is usually sufficient although certain patient populations may have large gradients between end tidal and arterial CO2 levels. These patients may need arterial blood gas monitoring for accurate diagnosis.

Answer 640

Pneumoperitoneum causes an increase in the intraabdominal pressure that causes the diaphragm to be pushed more cephalad. This causes collapse of lung tissue in the basal segments of the lungs causing decreased functional residual capacity (FRC), mismatching of the ventilation perfusion ratio (V/Q), and an increase in intrapulmonary shunting. All of these can lead to hypoxemia. If the patient will tolerate it, a small increase in the positive end-expiratory pressure (PEEP) and increasing inspired oxygen concentration can help decrease the effect.

Answer 641

Pneumoperitoneum also leads to mechanical and chemical induced effects from the carbon dioxide used. Mechanical effects include compression of the inferior vena cava which decreases venous return and can result in a decreased cardiac output. Ensuring adequate volume status can help counter this effect. Tachycardia may result from the increased sympathetic discharge, hypercarbia, and decreased venous return. On initial insufflation of the abdomen or during manipulation of the gastrointestinal tract, a significant bradycardia may be seen from increased vagal discharge. Asystole has been reported. Treatment consists of removing the insufflation and treating with an anticholinergic agent. Additionally, preventing large rapid increases in intra-abdominal pressure (to not above 12 mm Hg) may help. Some providers pretreat with an anticholinergic but this may lead to tachyarrhythmias in certain patients. Finally, positioning required for laparoscopic surgery can lead to alterations in physiology and potentially injury to the patient. Trendelenburg or reverse Trendelenburg is required with different degrees of bed side-to-side tilting. In terms of physiologic response, this can lead to pooling in the venous system (reverse Trendelenburg) or significant increases in cardiac return (Trendelenburg).

Answer 642

A pneumothorax will double in size by 10 minutes and triple by 30 minutes. N2O has a low blood:gas coefficient making it rather insoluble in blood. However, this insolubility means that N2O may diffuse into air-filled cavities, which will cause expansion. (e.g. middle ear, pneumothorax, or even endotracheal tube cuff)

Answer 643

Patients receiving heparin for more than five days should have a platelet count checked prior to epidural placement or catheter removal. ASRA guidelines recommend waiting 4-6 hours before epidural placement in patients receiving 5000 U subcutaneous heparin BID or TID.

Answer 644

The diagnosis of disseminated intravascular coagulation in pregnancy is generally clinical, followed by laboratory data. Because coagulation factors are increased in pregnancy, the typically seen prolongation of the PT and aPTT may not occur until significant bleeding has occurred. Expect to see a decrease in the platelet count, fibrinogen, and antithrombin III concentrations. This is also true of changes in platelet counts and D-dimer. Thus one should follow the trend of these laboratory markers.

Answer 645

The triad most expected in DIC is an increased PT/aPTT with decreased platelets and fibrinogen levels; however, this is often altered in pregnancy. The platelet count may be normal at the initiation of DIC thus the downward trend is a more important feature. This is also true of the PT and aPTT; they may be normal for some time despite significant disease progression. In pregnancy, these values tend to be in the normal range despite significant bleeding.

Answer 646

Treatment generally revolves around getting rid of the pathologic process causing the DIC while replacing coagulation factors and attempting to stop the proteolytic activity. Beyond this, treatment is supportive with hemodynamic and ventilatory support. If an invasive procedure is required or the patient is actively hemorrhaging, transfusion of blood products is likely needed. This includes fresh frozen plasma, cryoprecipitate, and/or fibrinogen concentrates. Goals typically include a PT/PTT within 1.5 times normal, fibrinogen levels above 150-200 mg/dL and platelet counts above 50,000.

Answer 647

Coronary perfusion pressure (CPP) is the difference between the aortic pressure and the ventricular pressure. Therefore, during systole, the LV reaches supraaortic pressures in order to drive blood forward. Accordingly, the LCA receives little, if any blood flow. In LV diastole, the aortic pressure exceeds ventricular pressure and this is the time when the LV is primarily perfused. Hence, CPP of the LV (CPPLV) is equal to difference between aortic diastolic pressure (AoDP) and left ventricular end diastolic pressure (LVEDP): CPPLV = AoDP - LVEDP.

Answer 648

Coronary blood flow is dependent on the gradient between aortic and ventricular pressures. The RCA and LCA maintain different blood flows throughout the cardiac cycle because of the differences between RV and LV pressures. The RV is continuously perfused throughout the cardiac cycle whereas the LV is primarily perfused during ventricular diastole.

Answer 649

In emphysema, the destruction of the alveoli and small distal airways leads to premature airway closure and air trapping during exhalation.

Answer 650

Infants and small children have larger extracellular fluid volumes by percentage of TBW and therefore require larger weight-based dosing of muscle relaxants.

Answer 651

Functional residual capacity is defined as the volume of air left in the lungs at the end of breathing, during tidal volume breathing. Functional residual capacity (FRC) is an important lung capacity. FRC is the most important determinant of the effectiveness of preoxygenation. FRC decreases in many different physiologic states including: obesity, supine positioning, pregnancy, and while under general anesthesia. FRC = Residual Volume + Expiratory reserve volume Or FRC = Total lung capacity – Inspiratory capacity

Answer 652

he expiratory reserve volume is the amount of air that can be actively exhaled at the end of a tidal volume breath

Answer 653

Residual volume is the amount of air left in the lungs at the expiratory reserve volume.

Answer 654

Vital capacity is the amount of air that is moved with a maximal inhalation and forced exhalation.

Answer 655

Causes of low FRC are PANGOS: Pregnancy, Ascites, Neonates, General anesthesia, Obesity, Supine position.

Answer 656

Factors that increase closing capacity are ACLS-SO: Age, Chronic bronchitis, LV failure, Smoking, Surgery, Obesity.

Answer 657

An increase in plateau pressure (Pplat) reflects decreased respiratory system compliance (CRS), which is composed of lung and chest wall compliance. Therefore, conditions that decrease CRS such as pulmonary edema, acute respiratory distress syndrome, transfusion-related acute lung injury, pneumothorax, pleural effusion, chest wall rigidity, fluid overload, obesity, abdominal insufflation, and abdominal compartment syndrome will increase Pplat during positive-pressure mechanical ventilation.

Answer 658

An airway pressure measured during a given inspiratory phase is the sum of pressures derived from airway resistance (Resistance * Flow) and respiratory system compliance (Volume/CRS). A peak airway pressure (Ppeak) is the peak in airway pressure reached at end inspiration. During volume-controlled ventilation, a brief end-inspiratory pause may follow. In the absence of flow, the resistive pressure becomes nil at which point the airway pressure solely reflects the CRS. This pressure is known as the Pplat and is available on certain ventilators. Any condition that increases the airway resistance will increase the Ppeak, but the Pplat will remain the same. A significant difference between the Ppeak and the Pplat, therefore, signifies the presence of increased airway resistance as seen in circumstances such as a kinked circuit, endotracheal tube obstruction, acute asthma attack, and bronchospasm. When both Ppeak and Pplat are elevated to the same extent, a decrease in CRS should be suspected.

Answer 659

An increase in plateau pressure (Pplat) reflects decreased respiratory system compliance (CRS), while an isolated elevation in peak airway pressure (Ppeak) represents increased airway resistance. Examples of issues that will increase plateau pressure include pulmonary edema, acute respiratory distress syndrome, transfusion-related acute lung injury, pneumothorax, pleural effusion, chest wall rigidity, fluid overload, obesity, abdominal insufflation, and abdominal compartment syndrome. Examples of issues that will increase peak pressure include kinked circuit, endotracheal tube obstruction, acute asthma attack, and bronchospasm.

Answer 660

change in airway resistance Examples of issues that will increase peak pressure include kinked circuit, endotracheal tube obstruction, acute asthma attack, and bronchospasm.

Answer 661

change in system compliance Examples of issues that will increase plateau pressure include pulmonary edema, acute respiratory distress syndrome, transfusion-related acute lung injury, pneumothorax, pleural effusion, chest wall rigidity, fluid overload, obesity, abdominal insufflation, and abdominal compartment syndrome.

Answer 662

CO = VO2 / (CaO2 - CvO2)

Answer 663

The adrenal gland consists of two grossly and functionally distinct zones. The outer cortex secretes steroid hormones in response to fluid/electrolyte shifts and ACTH. The adrenal medulla secretes catecholamines in response to direct innervation by preganglionic sympathetic fibers. Primary adrenal insufficiency is a result of intrinsic adrenal gland dysfunction. Secondary adrenal insufficiency is a result of decreased ACTH, which is most commonly due to exogenous steroid administration. The adrenal gland grossly consists of two functionally and developmentally different types of cells. The outer cortex is derived from mesoderm and produces steroid hormones (aldosterone and cortisol are the most relevant in anesthetic management) in response to fluid/electrolyte shifts and ACTH. The inner medulla is derived from ectodermal neural crest cells, which function as postganglionic neurons and release catecholamines (primarily epinephrine, but also norepinephrine and dopamine in smaller amounts) in response to sympathetic activation.

Answer 664

primary adrenal insufficiency (Addison disease) is a result of adrenal cortex dysfunction or destruction. This results in a combined mineralocorticoid/glucocorticoid deficiency. Aldosterone deficiency can result in hyponatremia, hypovolemia, hypotension, hyperkalemia, and metabolic acidosis. Glucocorticoid deficiency can manifest as weakness, fatigue, hypoglycemia, hypotension, and weight loss. For primary adrenal insufficiency, a mineralocorticoid coverage is needed thus methylprednisolone would be more appropriate for prophylaxis.

Answer 665

Secondary adrenal insufficiency can be due to disease or destruction of the pituitary gland, but the most common cause is due to exogenous glucocorticoid administration. Generally, mineralocorticoid production remains adequate in secondary adrenal insufficiency, so fluid/electrolyte derangements are often not seen. Therefore, treatment with an exogenous glucocorticoid (e.g. dexamethasone) would be appropriate. In clinical anesthesia practice, there is concern about adrenal insufficiency in patients who are on steroids or have taken large doses of steroids in the past few months. Since this would result in secondary adrenal insufficiency, dexamethasone would be an appropriate therapy for prophylaxis (i.e. methylprednisolone is not needed).

Answer 666

Sodium bicarbonate can cause a number of physiologic alterations including increased preload, decreased left ventricular contractility, and increased hemoglobin affinity for oxygen (left shift). Sodium bicarbonate administration is also associated with intracranial hemorrhage, especially with rapid administration in infants, and increased lactate production.

Answer 667

increased hgb addinift for oxygen; CO poisoning, increased pH; decreased temp, PCO2, 2,3 BPG

Answer 668

Histamine H2 receptor antagonists (e.g. cimetidine, ranitidine, famotidine, nizatidine) block histamine from inducing acidic gastric fluid secretion by parietal cells. This effectively raises gastric pH. Raising the gastric pH prior to induction of anesthesia can reduce the severity and risk of perioperative aspiration pneumonitis. The onset of action of cimetidine is approximately 60-90 minutes while that of newer histamine H2 receptor antagonists is approximately one hour. Ranitidine has a shorter onset of action, longer duration of action, and less side effects than cimetidine. Famotidine has a longer half-life than cimetidine or ranitidine.

Answer 669

Train-of-four fade and tetanic fade are due to blockade of α3β2 prejunctional receptors. The classic post-synaptic muscle-type nicotinic acetylcholine receptor (nAChR) present in the neuromuscular junction is composed of five subunits, two α1, one β1, one δ, and one ε (mature type). On the other hand, the neuronal-type pre-junctional nAchR is composed solely of α- and β-subunits. Just like those on the post-synaptic membrane, these are stimulatory (promote depolarization). Therefore, the presynaptic nAChR can create a positive-feedback that causes the release of further acetylcholine when a nerve is repeatedly or continuously stimulated.

Answer 670

The most common cause for claims made in the ASA Closed Claims Project database for death or brain damage is non-respiratory events. The top three factors leading to death and permanent brain damage are: 1) Cardiovascular events (pulmonary embolism, stroke, myocardial infarction, arrhythmia, undiagnosed conditions) 2) Respiratory events (inadequate ventilation, esophageal intubation, difficult airway) 3) Equipment issues (failure or misuse)

Answer 671

Diagnosis of malignant hyperthermia requires a muscle biopsy. Genetic testing is available, however, a negative result cannot completely rule out the diagnosis since not all mutations are known (and thus cannot be tested for). A positive result on genetic screening means the patient has the disease though due to excellent specificity. The fresh muscle is exposed to halothane and caffeine and the extent of the contraction is then measured. This is a reliable test and is the “gold standard” for diagnosis. The problem is that very few centers around the world actually perform this test, it is invasive and the sensitivity and specificity are 97% and 78% thus some false-positive results may occur.

Answer 672

Brachial artery catheterization is low risk and can be used for long-term monitoring. Potential complications include thrombosis, infection, and median nerve injury.

Answer 673

The anterior cardiac vein is associated with the RCA, the great cardiac vein is located with the LAD (left anterior descending artery), and the middle cardiac vein is associated with the PDA (typically from the RCA).

Answer 674

The risk of hypoglycemia after abrupt TPN discontinuation can be decreased by using TPN with a lower glucose-to-lipid ratio, stopping concomitant insulin infusions, and starting intravenous glucose with frequent blood glucose monitoring. Starting insulin upon TPN discontinuation increases the possibility of an acute hypoglycemic episode.

Answer 675

Box like A fixed upper airway obstruction or fixed large airway obstruction (e.g., foreign body, tracheal stenosis, large airway tumor) impairs BOTH inspiration and expiration leading to a flow-volume loop with plateaued and decreased inspiratory and expiratory flows.

Answer 676

A variable INTRAthoracic airway obstruction (e.g., distal tracheal tumor or mediastinal mass) produces a flow-volume loop with a plateaued EXPIRATORY curve and the flow rate is usually decreased. During expiration, intrathoracic pressure becomes positive which further decreases the airway diameter, enhances the degree of obstruction, and impairs airflow. The inspiratory curve is usually normal since the negative intrathoracic pressure generated during inspiration helps keep the airway open.

Answer 677

A variable EXTRAthoracic airway obstruction (e.g., vocal cord paralysis or dysfunction, proximal tracheal tumor, glottic strictures) produces a flow-volume loop with a plateaued INSPIRATORY curve and the flow rate is usually decreased. During inspiration, the negative inspiratory pressure causes the obstruction to increase. The expiratory curve is usually normal since the positive airway pressure generated during expiration helps keep the airway open.

Answer 678

Sepsis and septic shock are medical emergencies and should be rapidly and aggressively managed as soon as a diagnosis is made. Broad-spectrum antibiotics should be initiated within the first hour. Sepsis-induced hypoperfusion should be treated with at least 30 mL/kg of intravenous crystalloid within the first three hours. For patients with septic shock, vasopressor therapy should be used in combination with volume resuscitation to target an initial MAP of 65 mm Hg.

Answer 679

Complications of stellate ganglion blocks include vasovagal reactions, intravascular or spinal injection, and Horner syndrome (miosis, ptosis, anhidrosis, enophthalmos, and hyperemia).

Answer 680

Important side effects of amiodarone include bradycardia, hypotension, hypothyroidism, life-threatening hyperthyroid storm, pulmonary toxicity (with a pulmonary fibrosis appearance), prolonged QT interval, and elevated liver function markers.

Answer 681

Amiodarone is a class III antiarrhythmic agent with a primary effect of blocking potassium channels. It also blocks calcium and sodium channels to a lesser effect as well as α- and β-adrenergic receptors. The approved clinical use of amiodarone is limited to refractory ventricular arrhythmias. It has been shown to reduce the number of shocks required in patients with pre-existing implanted cardioversion devices. It is also commonly used in sustained supraventricular tachycardias with accessory pathway conduction and atrial fibrillation/flutter/tachycardia with congestive heart failure (CHF). It may be an effective prophylaxis for atrial fibrillation postoperatively. Recall that amiodarone is still the antiarrhythmic agent of choice in the setting of CHF or low ejection fraction.

Answer 682

Morphine is broken down to morphine-6-glucuronide (5-10%) and morphine-3-glucuronide (60%) by the liver minutes after administration. M3G contains no analgesic action in humans and may actually antagonize the analgesic effects of morphine to cause hyperalgesia. Agitation, myoclonus, delirium can also be seen. Effects from M6G include drowsiness, nausea/vomiting, coma, and respiratory depression. Patients with renal failure are more sensitive to the effects of morphine since it is excreted via the kidneys.

Answer 683

There are several differences between the infant and adult airway including the relatively larger tongue of an infant, a more cephalad larynx, angled vocal cords and an omega shaped epiglottis. The infant larynx is positioned more cephalic (C3-4 level) compared to an adult (C5-6 level). MRI and CT have confirmed the higher (more cephalad) position of the larynx in children and demonstrated that the hyoid bone is at the C2-3 level in infants and children up to 2 years old. The proximity of the tongue to the more superior larynx also makes visualization of the laryngeal structures more difficult because it produces a more acute angle between the plane of the tongue and the plane of the glottic opening. For this reason, a straight blade may be advantageous for direct laryngoscopy.

Answer 684

Renal regulation of blood pressure occurs by sensing Na+ ion concentration and renal perfusion pressure via the macula densa of the proximal tubules. The macula densa cells are part of the JGA. Renin is a protease synthesized in the JGA and serves to cleave angiotensinogen in the blood to yield angiotensin I. Angiotensin I is then cleaved to A2 by angiotensin-converting enzyme (ACE) in the lungs. Angiotensin II increases blood pressure by DIRECTLY causing arteriolar vasoconstriction throughout the body and glomerular arteriolar vasoconstriction (efferent >> afferent) in the kidneys. The latter effect ensures adequate glomerular filtration despite a sensed reduction in circulating volume. Angiotensin II INDIRECTLY increases blood pressure by stimulating the secretion of aldosterone from the zona glomerulosa of the adrenal glands. Aldosterone increases Na+ reabsorption and hence water retention within the collecting ducts. This increase in circulating volume creates a negative feedback loop which then suppresses the RAAS.

Answer 685

Angiotensin II increases blood pressure by DIRECTLY causing arteriolar vasoconstriction throughout the body and glomerular arteriolar vasoconstriction (efferent >> afferent) in the kidneys. The latter effect ensures adequate glomerular filtration despite a sensed reduction in circulating volume. Angiotensin II INDIRECTLY increases blood pressure by stimulating the secretion of aldosterone from the zona glomerulosa of the adrenal glands. Aldosterone increases Na+ reabsorption and hence water retention within the collecting ducts. This increase in circulating volume creates a negative feedback loop which then suppresses the RAAS.

Answer 686

Febrile reactions after transfusions are caused by pyrogenic cytokines and intracellular contents released by donor leukocytes.

Answer 687

Transfusion-related acute lung injury (TRALI) is an immune-mediated reaction that involves antibodies directed toward human leukocyte antigens (HLA), with the release of cytokines and vasoactive mediators that cause non-cardiac pulmonary edema.

Answer 688

Hemolytic transfusion reactions occur when recipient antibodies and complement system attack the transfused donor cells and cause intravascular hemolysis. A direct antiglobulin test (DAT), also known as a direct Coombs test, can differentiate a hemolytic from a febrile reaction.

Answer 689

Anaphylactoid reactions are clinically similar to anaphylaxis but are not IgE-mediated. They are caused by a release of mediators from mast cells and basophils, with activation of the complement system.

Answer 690

Morphine-3-glucuronide (M3G) is the major metabolite of morphine, but it does not bind to opioid receptors and possesses little or no analgesic activity. M3G may actually antagonize morphine, and this effect may contribute to both variability in response and resistance to morphine analgesic therapy. Morphine-6-glucuronide (M6G) accounts for nearly 10% of the morphine metabolite; it is a more potent μ-receptor agonist than morphine is and has a similar duration of action. It was reported that M6G contributes substantially to morphine’s analgesic effects, even in patients with normal renal function. Especially in patients with renal dysfunction, accumulation of M6G can lead to an increased incidence of adverse effects, including respiratory depression

Answer 691

Heliox is useful in situations where airway radius is decreased with resultant turbulent gas flow. With turbulent gas flow, resistance increases with increasing gas density. Helium has a decreased gas density as compared to oxygen or air and thus resistance to gas flow is reduced.

Answer 692

When combined with the Hagen-Poiseuille Law: Q=ΔP/R, where Q = gas flow rate, ΔP = difference in pressure, and R equal to resistance becomes: Q=ΔP*π*r4/(8*(length)(viscosity))

Answer 693

Flow pattern can be predicted by the Reynolds number. Reynolds number can be defined by the equation: Re = (Linear flow velocity)(tube diameter)(gas density) / gas viscosity Less than 2000 suggests laminar flow, above 4000 suggests turbulent flow, and between a mixture of the two. high viscosity--> more laminar flow

Answer 694

The solubility of a gas in a liquid is inversely related to temperature: as temperature decreases, solubility increases, and vice versa. The bottom line remains that the lower the temperature, the greater the solubility, and the lower the partial pressure.

Answer 695

The Henderson-Hasselbalch equation still applies, meaning pH is inversely related to PCO2. So when temperature decreases, PCO2 goes down and pH goes up.

Answer 696

Blood pH and the solubilities of gases in blood are inversely related to temperature while the partial pressures of gases are directly related to temperature. Accordingly, when arterial blood gas values are corrected to a colder temperature, PaO2 and PaCO2 decrease while pH increases.

Answer 697

Malignant hyperthermia can be distinguished from TS by the presence of muscle rigidity (present with MH, not a sign of TS), rate of EtCO2 rise (MH >> TS), the temperature increase (MH usually greater and faster than TS), and the degree of hypertension (TS > MH). On laboratory testing, hyperkalemia, elevated CK, and lactic acidosis are found with MH but usually not TS. Hypokalemia and elevated thyroid hormones are commonly seen with TS but not MH.

Answer 698

Terbutaline causes potassium to shift intracellularly which can potentially cause HYPOkalemia Terbutaline, along with other β2-agonists such as epinephrine, cause potassium to shift intracellularly as a direct effect of β2-receptor stimulation. Nonselective β-blockers can prevent this side effect of β2-agonists. Overall, this effect is generally short-lived. In obstetric patients given terbutaline infusions for management of preterm labor, potassium levels were found to return to baseline within 30 minutes of discontinuation of the infusion1

Answer 699

Administration of mannitol can cause a translocational hyperkalemia (B). Since mannitol is significantly hypertonic, intravascular administration causes water efflux from cells. Solvent drag then occurs by which intracellular potassium follows the water efflux and becomes intravascular.

Answer 700

Angiotensin II receptor blockers and ACE inhibitors both significantly decrease the release of aldosterone from the adrenal cortex. Since aldosterone causes secretion of potassium (by stimulating the Na+/K+ pumps in the renal distal tubules and collecting ducts), inhibition of its effects can lead to hyperkalemia

Answer 701

hyperkalemia Amiloride, triamterene, spironolactone, and eplerenone are the four potassium sparing diuretics. They work by blocking sodium reabsorption in the cortical collecting tubule and simultaneously increasing potassium reabsorption. Amiloride is a well tolerated drug whose only major side effect is hyperkalemia (A). Hyperkalemia is associated with peaked T waves on ECG, with T wave amplitude often surpassing that of the QRS complex as shown in the image. Increasing hyperkalemia may be visualized as a shortened QT interval, widening of the QRS, and PR prolongation. Concomitant use of ACE inhibitors may increase the risk of hyperkalemia in patients on potassium sparing agents

Answer 702

Furosemide, and all loop diuretics (e.g. bumetanide, ethacrynic acid), inhibit the sodium/potassium/2-chloride receptor in the ascending tubule loop of Henle. Potassium excretion is increased along with sodium and hypokalemia can result. Hypokalemia is characterized by T wave flattening or inversion and U waves on the ECG.

Answer 703

Hydrochlorothiazide works on the sodium/chloride cotransporter in the distal convoluted tubule increasing both sodium and potassium excretion. Thusly, hypo- and not hyperkalemia is an associated side effect. Thiazides also increase calcium reabsorption as electroneutrality is maintained. Hypercalcemia, hypomagnesemia, and hyponatremia may be seen.

Answer 704

Lithium toxicity is associated with hypermagnesemia. It is also associated with nephrogenic diabetes insipidus, which may be prevented or treated by blockade of the collecting tubule luminal sodium receptors with amiloride. Hypermagnesemia is characterized by PR interval prolongation and a widening QRS complex.

Answer 705

he K+ STAys with Spironolactone, Triamterene, Amiloride.

Answer 706

BARAICITY-- A variety of factors influence dermatomal spread following intrathecal administration of local anesthetics. Baricity is most correlated with the spread of hyperbaric solutions, while the total dose of medication administered is most correlated with the spread of isobaric or hypobaric solutions. Other factors that influence dermatomal spread include patient position and factors that decrease cerebrospinal fluid volume such as pregnancy, obesity, or advanced age.

Answer 707

Blood gas analysis electrodes include the Sanz electrode (measures pH), Severinghaus electrode (measures PCO2), and Clark electrode (measures PO2).

Answer 708

The majority of anesthetic agents may be used at normal doses in emergency cesarean deliveries. Inhaled anesthetic agents exert the most powerful negative effect on the neonate, and exposure in-utero should be minimized immediately prior to delivery through communication with the surgical team and rapid delivery of the fetus following induction of anesthesia. Benzodiazepines have been associated with fetal hypotonia ("floppy baby syndrome") when administered during labor and may have detrimental effects for hours to weeks following delivery.

Answer 709

Contraindications to acute normovolemic hemodilution include preoperative anemia, cardiac disease, recent cerebral vascular accident, clinically significant renal or liver disease, and/or active infection.

Answer 710

Acute normovolemic hemodilution (ANH) is a useful method of autologous blood procurement in patients with rare blood cell antibodies and/or preference for not receiving allogeneic blood transfusions that are having surgical procedures with anticipated large amounts of blood loss. ANH involves removing units of blood from a patient prior to the start of and during a surgical procedure while simultaneously maintaining intravascular volume with intravenous fluids. The removed whole blood is transfused back into the patient at the end of the surgical procedure (within 6-8 hours of collection) and eliminates infectious and immune reaction risks from allogeneic blood transfusions.

Answer 711

The best initial treatment of the patient with hemodynamically unstable supraventricular tachycardia (SVT) is synchronized cardioversion.

Answer 712

The carotid sinus is a pressure regulating system. In high-pressure settings, the afferent impulse is transmitted by the glossopharyngeal nerve to the nucleus tractus solitarius, which results in inhibition of the sympathetic system and activation of the parasympathetic systems to reduce blood pressure and decrease heart rate.

Answer 713

Diltiazem is unique among the calcium channel blockers in its ability to act on both smooth muscle and cardiac muscle at clinically-relevant doses. Thus, it acts as both a vasodilator and a cardiac depressant, decreasing peripheral vascular resistance and dilating coronary arteries with little-to-no reflex tachycardia.

Answer 714

Transfusion of allogeneic packed red blood cells can lead to transfusion-related immunomodulation (TRIM). The risk of TRIM can be reduced by leukocyte reduction. Perioperative transfusion may increase the risk of bacterial infection, cancer recurrence, and mortality. Thus, it is prudent to avoid unnecessary administration of blood products.

Answer 715

Bupivacaine has the lowest cardiac-to-CNS dose toxicity ratio (2:1) AND the highest relative potency for cardiac toxicity amongst the local anesthetics. This cardiac toxicity is due to bupivacaine’s stronger affinity for both resting and inactivated sodium channels within the myocardium compared with other local anesthetics. All local anesthetics slow cardiac conduction to some degree. They may produce both direct and indirect cardiotoxicity through blockage of the INTRACELLULAR portion of cardiac SODIUM ion channels. This results in impairment of cardiac automaticity and conductance of cardiac action potentials. This can be observed on ECG as prolongation of the PR interval and widening of the QRS complex. Bupivacaine has been shown to dissociate from sodium channels during diastole at a rate much slower than lidocaine. `This slower dissociation impairs complete recovery of sodium channels following hyperpolarization.

Answer 716

Albumin and α1-acid glycoprotein are the major plasma proteins to which opioids bind. Therefore, hypoalbuminemia will increase the free fraction of opioids which would normally decrease dosing requirements. However, burn patients develop very rapid tolerance to opioids, particularly fentanyl, due to the large amounts administered to control their severe pain

Answer 717

Severe burns lead to hypoalbuminemia which increases the free fraction of many anesthetic drugs including benzodiazepines and opioids. Lower doses of benzodiazepines should be considered, while higher doses of opioids are usually required due to the rapid development of tolerance. Insulin resistance is seen due to increased catecholamine and corticosteroid levels. Proliferation of extrajunctional acetylcholine receptors leads to exaggerated hyperkalemia with succinylcholine use and resistance to nondepolarizing neuromuscular blockers.

Answer 718

Chest wall stiffness, flattening of the diaphragm, and loss of lung elasticity are all changes associated with aging. Aging results in an increase in FRC, RV, and CC. There is a concomitant reduction in IC and TLC (see figure above). Closing capacity is the volume remaining in the lungs during expiration when small airways (respiratory bronchioles) begin close.

Answer 719

Treatment for intraoperative thyroid storm includes first removing the offending stimulus or precipitating event. Thyroid hormone release can be blocked by sodium or potassium iodide administration, however only after a thyrostatic medication such as propylthiouracil has been given. Supportive therapies include: - Intravascular volume should be restored with fluid administration - Tachycardia may be managed with esmolol and/or propranolol - Digoxin or beta blockers can treat arrhythmias - Hydrocortisone or dexamethasone can decrease hormone release - Antipyretics (e.g. acetaminophen) and cooling blankets may be used to control the hyperthermia.

Answer 720

Although supportive measures improve morbidity and mortality, the most important step to limit the signs and symptoms of thyroid storm is blocking thyroid hormone release and limiting its production. Propylthiouracil (PTU) and methimazole (MTZ) are both medications that can be used to inhibit the production of thyroid hormone (T4). In addition, propylthiouracil blocks the peripheral conversion of T4 to T3 - this makes PTU favorable over MTZ. These anti-thyroid drugs can be used as either definitive therapy or as a bridge to treatment with surgery or radioactive iodine. Potassium iodide can be given orally in high concentrations to inhibit the release of hormone from a high functioning gland. The effects are short-lived, however. Radioactive iodine (iodine-131) can be given orally to either severely restrict or completely destroy the thyroid gland. Because iodine is picked up almost exclusively by the thyroid gland, and even more so by overactive thyroid cells, the effect of treatment is completely localized to the thyroid gland.

Answer 721

Elderly patients have a decrease in parasympathetic tone and increase in sympathetic tone at rest. Other cardiovascular changes occurring in the elderly include a reduction in ischemic preconditioning and worsening diastolic dysfunction with increased left atrial pressures. Systolic function is often preserved in the otherwise healthy elderly patient.

Answer 722

Prerenal . Intrinsic/ATN . Postrenal BUN:creatinine ratio > 20 < 15 > 15 FENa < 1% > 2% > 4% Urine Sodium (UNa) < 10 mEq/L > 20 mEq/L > 40 mEq/L Urine Osmolality (UOsm) > 500 mOsm/kg < 350 mOsm/kg < 350 mOsm/kg

Answer 723

The primary strategies that can help preserve renal function in the perioperative period include maintaining renal perfusion pressure (ensuring adequate cardiac output and MAP and treating any conditions that may cause venous congestion) and avoiding or limiting exposure to nephrotoxins such as aminoglycosides and iodinated contrast dye. Forced diuresis, N-acetylcysteine, dopamine, fenoldopam, nesiritide, mannitol, and urine alkalinization have very limited or no benefit for renal preservation.

Answer 724

The goal for general anesthesia induction in the patient with cardiac tamponade is to keep the heart fast (quick heart rate), full (maximize preload), and forward (avoiding cardiac depressants). The stroke volume is limited in these patients given the extracavitary pressure thus the tachycardia is a mechanism to preserve cardiac output. In addition, another compensatory mechanism is peripheral vasoconstriction to preserve venous return and mean arterial pressure. Anesthetic management involves the following: increased intravascular volume with either crystalloid or blood products if necessary, maintenance of spontaneous ventilation as to avoid the decreased preload positive pressure breaths would cause, as well as avoidance of drugs that decrease blood pressure, slow heart rate, or have myocardial depressant effects. Given the options listed, ketamine, with its sympathomimetic effects and less cardiac depressing features, in addition to the preservation of spontaneous ventilation, tends to be the preferred induction agent.

Answer 725

In non-depolarizing blockade, twitch fade on train-of-four stimulation is due to an increase of occupancy of ACh receptor by the non-depolarizing blocker as well as a diminishing release of ACh into the neuromuscular junction with each successive twitch. In depolarizing blockade, this phenomenon is caused by a phase II block of presynaptic ACh receptors, which also results in diminishing ACh release with each twitch.

Answer 726

Local anesthetics are weak bases that bind to the intracellular portion of voltage-gated sodium channels and prevent nerve conduction. Although the “active” form of local anesthetics is the ionized form [charged cation (BH+)], the speed of onset of effect is determined by the proportion of local anesthetic in the unionized [basic, uncharged (B)] form. Unionized molecules pass through the lipid membrane and reach their targets easier than ionized molecules. The onset of action of local anesthetics is primarily a result of lipid solubility and pKa. The more lipid soluble, the more quickly the molecule can pass through the cell lipid membrane and reach its sites of action. The pKa of a drug refers to the pH at which the drug exists in equal parts of ionized and unionized forms. A local anesthetic with a lower pKa will have a greater unionized fraction (and generally faster onset) at physiologic pH (7.4) than a local anesthetic with a higher pKa (greater ionized fraction at physiologic pH and generally slower onset).

Answer 727

Local anesthetics are formulated as hydrochloride salts with a pH slightly <7, as the ionized molecule is more soluble and stable than the free base. Once injected, the local anesthetic solution is quickly buffered to the pH of the tissue. The addition of bicarbonate to a local anesthetic mixture speeds the onset of action by raising the pH of the anesthetic solution so that more of the unionized fraction is available. Note that bicarbonate should only be mixed just prior to injection as the mixture becomes less stable for storage.

Answer 728

Epinephrine causes local vasoconstriction, which prolongs the duration of effect of local anesthetics. By decreasing local blood flow, local anesthetic is maintained in the area of injection. Epinephrine solutions must be acidic (pH 2-5) to preserve the epinephrine. The addition of typical amounts of fresh epinephrine to plain local anesthetics (pH ~6) has little effect on the speed of onset of local anesthetics. However, premixed local anesthetic solutions with epinephrine are significantly more acidic (pH 3-4); this drives the local anesthetic to its ionized form, thus potentially slowing speed of onset.

Answer 729

Local anesthetic concentration also affects the speed of onset. The greater the concentration, the faster the speed of onset since there is a steeper concentration gradient to drive local anesthetics intracellularly. This is how chloroprocaine (pKa 9, which would predict a slow onset) has such a rapid onset: a 3% solution is highly concentrated compared to, for example, 0.25% bupivacaine (pKa 8.1).

Answer 730

Tissue inflammation slows the onset of effect of local anesthetics. Inflammation leads to a localized acidic environment. This drives more local anesthetic into its ionized form (local pH is farther from local anesthetic pKa), thus decreasing the speed of onset. Additionally, increased blood flow associated with inflammation washes local anesthetics away from their site of action.

Answer 731

The onset of effect of a local anesthetic is affected by its concentration (higher is faster), lipid solubility (higher is faster), pKa (lower is faster), and environment pH (higher is faster). Anything that increases the concentration or proportion of local anesthetic in its unionized form will speed the onset of analgesia.

Answer 732

CRPS Treatment Algorithm (Adapted from Rho et al. Mayo Clin Proc 77: 174, 2002) Step 1: physical therapy Step 2: TCA, gabapentin, mild opioid if needed for physical therapy Step 3: diagnostic sympathetic block Step 4: somatic block of sympathetic block fails Step 5: spinal cord stimulator / intrathecal medications

Answer 733

Hyperparathyroidism can cause hyperchloremia and increase renal bicarbonate loss, which may result in a normal anion gap metabolic acidosis. Hyperparathyroidism commonly presents with recurrent nephrolithiasis, abdominal pain, depression, and bone pain. It is typically due to a single active parathyroid adenoma, parathyroid hyperplasia, parathyroid malignancy, or chronic renal insufficiency. In primary hyperparathyroidism, parathyroid hormone (PTH) levels are elevated. Parathyroid hormone has been shown to be an important inhibitor of renal bicarbonate reabsorption. Increased renal bicarbonate loss leads to a metabolic acidosis. Furthermore, PTH has been shown to inhibit the sodium chloride cotransporter in the distal convoluted tubule of the nephron leading to hyperchloremia. Although not particularly common, patients with hyperparathyroidism may have a lower than normal pH, slightly decreased PaCO2 due to respiratory compensation, a decreased bicarbonate level, and a normal anion gap.

Answer 734

Epinephrine is a first-line drug for treatment of severe bradycardia and hypotension from a high spinal.

Answer 735

Oxygen regulators are present in anesthesia machines to help ensure proper oxygen delivery and backup. The first-stage regulator will shut off the lower pressure oxygen cylinder tanks when the higher-pressure oxygen pipeline is sensed. The second-stage regulator, if present, will decrease pressure to slightly above atmospheric to ensure smooth constant flow of gases.

Answer 736

Stimulation of β2 adrenergic receptors causes bronchodilation while M3 receptor stimulation causes bronchoconstriction. Epinephrine causes significant bronchodilation. Norepinephrine does not cause significant bronchial smooth muscle relaxation as it is more β1-selective.

Answer 737

Patients with long QT syndrome (LQTS) and a history of cardiac arrest warrant automatic cardioverter-defibrillator placement. Anesthesia in patients with untreated LQTS carries a very high risk of intra-operative malignant ventricular arrhythmias that may be refractory to treatment. Long QT syndrome (LQTS) is a cardiovascular disorder that results from mutations in the cardiac ion channels. It consists of prolonged ventricular repolarization and manifests as prolongation of the QT interval on the ECG. About 60% of patients with this mutation will manifest symptoms that range from recurrent syncope and seizure to cardiac arrest. Diagnosis occurs via ECG which shows a QTc of > 440 ms. Congenital LQTS is a syndrome of familial QT interval prolongation with variable inheritance patterns – autosomal dominant or recessive. Three ion channel abnormalities have been identified: LQT1 (K+), LQT2 (K+), and LQT3 (Na+). Congenital LQTS may occur with deafness (Jervell, Lange-Nielsen syndrome) or without deafness (Romano-Ward syndrome).

Answer 738

Cardiac conditions associated with the highest risk of adverse outcome from IE: Prosthetic cardiac valves Previous infective endocarditis Valvular heart disease following cardiac transplantation Unrepaired cyanotic congenital heart disease (CHD), including palliative shunts and conduits Repaired CHD with prosthetic materials/device(s) placed in first 6 months following the procedure Repaired CHD with residual defects The committee also recommended that patients with the above cardiac conditions not undergo body piercing. Prophylaxis is recommended only for patients with the underlying cardiac conditions noted above in the following situations: Dental procedures with manipulation of gingival tissue or perforation of oral mucosa Respiratory tract procedures involving incision or biopsy of mucosa (e.g., bronchoscopy with biopsy, lung resection) Patients with infected skin, skin sutures, or musculoskeletal tissue

Answer 739

Hypocalcemia prolongs phase 3 of the cardiac myocyte action potential which lengthens repolarization time. These effects can manifest as a prolongation of the QT interval on ECG.

Answer 740

Phase 0 is a fast inward depolarizing current caused by opening of sodium channels. Phase 1 is the partial repolarization phase caused by inactivation of the sodium channels and a transient outward current of potassium ions. Phase 2 is the plateau during which the membrane slowly repolarizes from opening of sarcolemmal L-type calcium channels (L for long-lasting). Phase 3 involves the completion of repolarization. This occurs due to the outward flow of potassium via two types of ion channels: voltage-gated channels causing a delayed outward potassium current and calcium-activated potassium channels that open due to elevated calcium levels within the sarcoplasmic reticulum (SR). P4: resting

Answer 741

Complete heart block is associated with ischemia involving the right coronary artery and typically involves the inferior wall. The treatment of third degree heart block is ventricular pacing: either transcutaneous, transvenous, or via a permanent pacemaker.

Answer 742

About 85% of the population is right-dominant with the RCA giving rise to the PDA. The AV node is supplied by a branch of the RCA in right-dominant patients and complete heart block is most commonly caused by a myocardial infarction involving the RCA. about 15% of patients, the left circumflex gives rise to the PDA and these are known as left-dominant patients. A small portion of patients get dual blood supply to the PDA and are known as co-dominant.

Answer 743

The LAD artery supplies the anterior wall of the heart, the interventricular septum, the bundle branches, and the Purkinje system. A blockage of the LAD could also cause heart block by damaging the distal conducting system.

Answer 744

The left circumflex artery supplies the posterior and lateral walls of the left ventricle. In about 15% of patients, the left circumflex gives rise to the PDA (e.g. left-dominant). In these patients, the left circumflex also supplies the AV node and blockage could cause complete heart block. However, in the majority of patients it would be the RCA that supplies the AV node.

Answer 745

From a respiratory standpoint, the positive pressure is continuously delivered during inspiration and expiration. CPAP provides the necessary pressure during inspiration needed to recruit alveoli that have been collapsed and keeps these alveoli open by providing positive pressure during expiration (or PEEP). This recruitment of alveoli increases lung volume, specifically, functional residual capacity (FRC). As the FRC increases, lung compliance also increases. Alveolar recruitment decreases right to left intrapulmonary shunt. CPAP has shown to also reduce surfactant depletion, which will further maintain lung compliance. This is beneficial in infants with respiratory distress. As more alveoli are recruited, there is an increase in alveolar surface area. This results in increased oxygenation and ventilation; arterial pO2 increases and arterial pCO2 decreases.

Answer 746

From a cardiovascular standpoint, CPAP reduces pulmonary vascular resistance by improving hypoxia and hypercarbia. This decreases the afterload in the right-heart. However, the positive pressure increases intrathoracic pressure and leads to decreased venous return. The reduced venous return can decrease cardiac output due to preload reduction. However, some studies have shown that CPAP increases cardiac output in patients with cardiogenic pulmonary edema.

Answer 747

Hetastarch is a colloid solution that is comprised of 6% hydroxyethyl starch, electrolytes, glucose, and lactate. Studies have shown that administration of hetastarch inhibits agonist-induced expression of glycoprotein IIb-IIIa complex availability on platelets. Thus, because of the decreased availability of the glycoprotein IIb-IIIa complex, platelets are not able to achieve the appropriate conformation to bind fibrinogen, which negatively affects platelet aggregation. It also leads to reduction in factor VIII and von Willebrand factor

Answer 748

Left atrial enlargement can be identified by a convex left atrial appendage contour and the “double density sign” on the posteroanterior view of a chest radiograph. This may be seen with severe mitral stenosis.

Answer 749

No single test can predict the success or failure of a wean from ventilatory support. A maximum inspiratory pressure of > -20 cmH2O (i.e. -20 to 0 cmH2O) is a fairly sensitive predictor of wean failure, but a value of < -20 cmH2O is not necessarily predictive of a successful wean. All bedside tests should be taken in aggregate with a patient's overall clinical status in order to determine their adequacy for a ventilatory wean.

Answer 750

An RSBI of < 105 is thought to represent appropriately slow and deep tidal volume breathing which is potentially indicative of a successful wean.

Answer 751

A P/F ratio of > 200 generally represents adequate oxygen transfer and may lend support for a prediction of a successful ventilatory wean.

Answer 752

While airway leak tests may not necessarily be predictive of extubation success, an airway leak at < 12-15 cmH2O is thought to represent a patent airway and may be reassuring for a successful wean.

Answer 753

Presynaptic calcium channels are destroyed in Lambert-Eaton myasthenic syndrome (LEMS).

Answer 754

Lambert-Eaton myasthenic syndrome, also known as myasthenic like syndrome, is a paraneoplastic syndrome associated with small-cell lung cancer (though can be associated with other conditions such as sarcoidosis and collagen vascular disease and other cancers such as lymphoma, testicular and ovarian cancer). It is typically antibody-mediated and involves the destruction of the presynaptic voltage-gated calcium channels in the NMJ. This leads to a decrease in secretion of acetylcholine (Ach). Muscle weakness usually improves with muscle usage. It typically involves the proximal extremities and rarely progresses to ocular or bulbar symptoms. The deep tendon reflexes are typically absent or depressed and muscle pain is common. Patients are typically older than myasthenia gravis patients and are more commonly male (often males older than 40). Treatment involves a drug called 3,4 diaminopyridine (prolongs action potential and increases Ach release), immunosuppression, sometimes steroids, and rarely plasmapheresis. Anticholinesterases play no role in the treatment of LEMS. Also, expect autonomic dysfunction as this is commonly associated with LEMS.

Answer 755

Myasthenia gravis (MG) is an autoimmune disorder involving antibodies that attack the postsynaptic acetylcholine (Ach) receptor in the neuromuscular junction (NMJ) or other postjunctional muscle membrane proteins. This leads to a decrease in the total number of functioning receptors. Up to 90% of patients are antibody positive. The hallmark of MG is muscle weakness that is worsened by usage and improved with rest. The severity of MG is different in each patient and tends to be more severe with increasing age of onset. Ocular involvement is very common, even in disease remission. Bulbar symptoms are slightly less common, and severe disease leading to proximal muscle weakness and respiratory failure is fairly uncommon. Treatment for MG includes oral anticholinesterases (such as pyridostigmine), steroids, immunosuppressants, and IVIG. Plasmapheresis may be warranted in the acute setting. The thymus functions to produce T-lymphocytes which aid in cell-mediated immunity and antibody production. Between 15-60% of patients with MG will develop a thymoma or thymic hyperplasia. Thymectomy produces remission or improvement in symptoms in 75% of patients. Thymectomy is clearly indicated if thymoma is present. Patients with myasthenia gravis may experience crises where they get extreme weakness and respiratory failure and may require mechanical ventilation. Crises may occur with poor medical management, stress, hyperthermia and pulmonary infections. Cardiac manifestations may also occur with myocarditis, LV diastolic dysfunction, atrial fibrillation and AV block all possible. 20-40% of parturients will have worsening of MG symptoms and infants born to mothers with MG will have myasthenia after birth from the passage of the IgG antibodies across the placenta in 15-20% of these neonates and may last for weeks at a time. Given the extreme sensitivity to nondepolarizing NMB, avoidance of the use of these agents is warranted if possible. Succinylcholine still can be used at doses of 1.5-2.0 mg/kg but if on significant doses of pyridostigmine, may last longer than expected

Answer 756

Disease LEMS Myasthenia Gravis Pathophysiology Autoimmune destruction of pre-synaptic voltage-gated Calcium Channels Autoimmune destruction of post-synaptic Ach receptors or other postjunctional membrane proteins Manifestations Proximal limb weakness (UE > LE), muscle pain common, absent or reduced reflexes, improves with use Eye and bulbar symptoms primarily affected, muscle pain uncommon, reflexes typically normal, worsens with use Co-existing disease Small-cell lung cancer Thymoma, thymic hyper or hypoplasia Gender Male > Female Female > Male Treatment Treat the underlying cause, steroids, IVIG, immunomodulation Anticholinesterase, steroids if anticholinesterase not working, IVIG or plasmapheresis acutely, immunomodulation Response to muscle relaxants Sensitivity to both non-depolarizing NMB and succinylcholine Sensitivity to non-depolarizing NMB, resistance to succinylcholine

Answer 757

Some predictors of postoperative respiratory failure requiring mechanical ventilation of MG patients are: - Disease Duration > 6 years - Daily Pyridostigmine dose > 750 mg - FVC < 2.9 liters - Other chronic lung disease not related to MG

Answer 758

Postpartum pituitary gland necrosis, also known as Sheehan syndrome, is related to postpartum hemorrhage and can result in panhypopituitarism.

Answer 759

CVP: 2-6 mmHg PCWP: 6-12 mmHg CI: 2.5-4 L/min/m2 SVR: 800-1200 dynes*sec/cm5

Answer 760

Patients who aspirate when supine are most likely to collect secretions in the posterior segment of the right lower lobe.

Answer 761

reduced effect Selective serotonin reuptake inhibitors (SSRIs), specifically fluoxetine and paroxetine, significantly inhibit CYP2D6 and slow the conversion of hydrocodone to hydromorphone within the liver. While oral hydrocodone itself has an analgesic potency that is comparable to morphine when it is administered orally, its metabolite hydromorphone has roughly 4 times greater analgesic efficacy. Inhibition of the CYP2D6 enzyme may, therefore, result in less clinical analgesic effect than otherwise might be gained from the ingestion of hydrocodone.

Answer 762

Carcinoid syndrome has several pathologic consequences including cutaneous flushing, asthma, diarrhea, and right-sided heart disease.

Answer 763

The diagnosis of a carcinoid tumor is generally made by detecting high levels of 5-hydroxyindoleacetic acid, a breakdown product of serotonin, in the urine (B). Treatment then varies based on location and metastases and can include surgical resection and/or medical treatment with octreotide or other drugs. When caring for these patients in the operating room, octreotide should also be readily available. Release of serotonin or other vasoactive substances from these tumors can lead to hypotension and hemodynamic instability. Octreotide is the first line treatment in this circumstance.

Answer 764

The cricothyroid muscle is innervated by the external branch of the superior laryngeal nerve, the external laryngeal nerve.

Answer 765

CaO2 = (Hgb * 1.34 * SaO2) + (0.003 * PaO2)

Answer 766

CBF = CPP / CVR or CBF = (AoDP – LVEDP) / CVR.

Answer 767

Myocardial oxygen supply is affected by AoDP, LVEDP, heart rate, Hgb, and CVR. Left ventricular systolic pressure affects myocardial oxygen demand.

Answer 768

Pregnancy has been called a state of chronically compensated disseminated intravascular coagulopathy. Factors that increase include I (fibrinogen), VII, VIII, IX, X, XII, and von Willebrand factor which peak at the time of parturition.

Answer 769

Factors that decrease include XI, XIII, antithrombin III, and tPa. Also, resistance to activated protein C occurs as well as a decline in the level of protein S.

Answer 770

A dilutional and consumptive thrombocytopenia occurs which usually results in a decrease of 10% in platelet count. Other hematologic changes that occur include an increase in red blood cell mass of 20-30% and an increase in plasma volume of 40-50% resulting in dilutional anemia. Other factors altering the hematologic makeup of pregnant patients include the presence of preeclampsia or HELLP syndrome and peripartum accidents such as placental abruption.

Answer 771

Advantages of including dilute epinephrine in local anesthetic/opioid solutions for epidural labor analgesia include more rapid onset and longer duration of analgesia, enhanced analgesia due to α-1 receptor stimulation, and decreased local anesthetic/opioid requirements. Disadvantages include increased intensity of motor blockade, cost, and increased risk of drug error. Epinephrine may also cause a clinically insignificant reduction in uterine activity via uterine β-2 receptor stimulation.

Answer 772

Urine output of < 2 mL/kg/hr is consistent with mild dehydration in a newborn.

Answer 773

Factors that increase statistical power include: increasing sample size, increasing the effect size, increasing alpha (e.g. p-value), and reducing population variability (e.g. standard deviation).

Answer 774

A statistical hypothesis is formed for a given experiment to establish statistical parameters of the study for analysis. This starts with a null hypothesis which states there is no difference between two groups. Rejecting the null hypothesis when it is true is called type I or alpha error (false positive). Alpha is chosen by the experimenters and is most often 0.05 and is compared to the p-value. Failing to reject a null hypothesis that is false is known as type II or beta error (false negative). The power of a test is the probability that there will not be a type II error. This will be (1 - beta error). Beta error is often chosen as 0.2.

Answer 775

CPPLV = AoDP – LVEDP

Answer 776

Delays in analysis and exposure of a sample to room air are the two most common sources of error in blood gas analysis. A delay will result in decreased PaO2, pH, and base excess values and an increase in PaCO2. Entrainment of room air will tend to cause the PaO2 value of the sample to approach the PO2 of room air (159 mmHg at sea level) and result in a decreased measured PaCO2.

Answer 777

The expression differential blockade is used to describe how neuraxial anesthesia progresses and recovers in a predictable manner. For example, sensation to cold is lost early and thus can be used to evaluate the progression of the block. Differential blockade with local anesthetics results in sympathetic blockade first, followed by pain/sensory blockade, then motor blockade last. This is (at least in part) explained by differential susceptibility of nerve fibers to local anesthetics being A-delta, A-gamma > A-alpha, A-beta > C. "DGAB-C!"

Answer 778

Chronic dantrolene use has been associated with liver dysfunction and potentially fatal liver failure, thus liver function testing (LFT) should be routinely monitored. Dantrolene is most commonly recognized as the definitive treatment for malignant hyperthermia and may be useful in the setting of neuroleptic malignant syndrome, serotonin syndrome, and Ecstasy poisoning/overdose. However, it can also be used chronically (oral form) for management of muscle spasticity associated with conditions such as cerebral palsy, multiple sclerosis, and following strokes.

Answer 779

Cerebral autoregulation is maintained with barbiturates (C). Thiopental, like all barbiturates, causes a dose-dependent reduction in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen consumption (CMRO2).

Answer 780

Risk factors found to be independent predictors of difficult mask ventilation vary somewhat between studies, but often include: - Obstructive sleep apnea or history of snoring - Age older than 55 years - Male gender - Body mass index of ≥ 30 kg/m^2 - Mallampati classification III or IV - Presence of a beard - Edentulousness - Limited mandibular protrusion - Neck radiation changes

Answer 781

Surgery during pregnancy carries several risks to both the mother and fetus. Elective surgery should wait until 2-6 weeks following delivery to allow the mother get back to non-pregnant physiologic state. If surgery must be performed during pregnancy, it’s best during the second trimester to mitigate the risks. During surgery it is important to maintain maternal blood pressure as uterine perfusion is dependent on blood pressure due to lack of autoregulation. It is also prudent to avoid hyperventilation as decreased PaCO2 can cause uterine vasoconstriction. Maintenance of maternal PaO2 is also prudent to ensure adequate delivery to the fetus. An increase in miscarriage (< 20 weeks GA), abortion (> 20 weeks GA), low birth weight and preterm labor are all known risks.

Answer 782

Signs and symptoms of diabetic autonomic neuropathy include loss of heart rate variability, resting tachycardia, dysrhythmias, impaired ventilatory responses, gastroparesis with increased risk of aspiration on induction, and unawareness of hypoglycemia.

Answer 783

Hyperkalemia is defined as a serum potassium >5.5 mEq/L. Hyperkalemia can be caused by reduced glomerular filtration, transcellular shifts, and hypoaldosteronism. Hyperkalemia due to extracellular shifts may be secondary to acidosis, rhabdomyolysis, or drugs. Drugs which can cause hyperkalemia include beta blockers, nonsteroidal anti-inflammatory drugs, spironolactone, heparin, and angiotensin-converting enzyme inhibitors. Patients who are hyperkalemic can present with weakness, palpitations, bradycardia, nausea, vomiting, and paralysis. Patients with chronic hyperkalemia are often asymptomatic.

Answer 784

Treatment for hyperkalemia includes calcium, albuterol, insulin, sodium bicarbonate, sodium polystyrene sulfonate, loop diuretics, and/or hemodialysis. Calcium chloride and calcium gluconate stabilize cardiac myocyte membranes. Though onset is immediate, it has no effect on serum potassium levels and thus is not used to lower potassium levels. Since they cause no change in potassium levels there is no measure of change over time, thus the change cannot be defined as being rapid or slow. Albuterol has an onset of action of 10-30 minutes. It can be given by inhalation or intravenously and functions by stimulating β2 receptors which drive potassium intracellularly. Standard inhaled dosing may lower serum potassium by 1-1.5 mEq/L. Regular insulin drives potassium intracellularly. Its onset of action is 15-20 minutes and peak effect may occur after an hour. It can be given with or without dextrose depending on whether hyperglycemia is also present. A dose of 10 units lowers serum potassium by approximately 1 mEq/L. Sodium bicarbonate is useful in the setting of metabolic acidosis. Its onset, when given intravenously, is 15 minutes and an infusion of 2-4 mEq/min lowers serum potassium by 0.5-0.75 mEq/L. Sodium polystyrene can be given orally or rectally with an onset of action of 1-2 hours. A dose of 25-50 mg lowers serum potassium by 0.5-1 mEq/L.

Answer 785

Treatment for hyperkalemia includes, but is not limited to, albuterol, insulin, sodium bicarbonate, sodium polystyrene sulfonate, loop diuretics, and/or hemodialysis. Albuterol and insulin are rapid acting and the most effective pharmacologic interventions for acutely lowering serum potassium. Calcium does not affect potassium levels

Answer 786

It is recommended that great caution be used when injecting additional local anesthetics within 12 to 18 hours of a tumescent anesthesia. Plasma concentrations may peak more than 8 to 12 hours after infusion of tumescent anesthesia.

Answer 787

Epinephrine is an endogenous catecholamine. It is sympathomimetic and activates both types of alpha and beta receptors. Because of the many synapses in the sympathetic nervous system (SNS) prior to innervating the target organ, epinephrine amplifies the SNS signaling with widespread effects. This is important to prepare the body for the “fight or flight" response by increasing cardiac output, making glucose available, slowing digestion, shunting blood flow preferentially to vital organs, and improving far vision. Epinephrine's target organ effects depend on the type of adrenergic receptor that is present. Alpha receptors are found on the eye causing mydriasis, on sweat glands causing diaphoresis, and throughout the gastrointestinal tract causing relaxation. Beta receptors are found on the heart increasing chronotropy and inotropy, on the lungs causing bronchodilation, and on the liver causing glycolysis and gluconeogenesis. Some organs such as blood vessels have both alpha and beta receptors. The effect of epinephrine depends on which receptor is activated. Alpha receptors cause vasoconstriction whereas beta receptors cause vasodilation. At lower doses, epinephrine's beta effects predominate leading to vasodilation. At higher doses, epinephrine's alpha effects cause vasoconstriction.

Answer 788

Epinephrine binds alpha receptors on the sweat glands causing increased secretion. Postganglionic neurons in the sympathetic nervous system use norepinephrine, with the exception of sweat glands which use acetylcholine.

Answer 789

Sodium bicarbonate can be administered perioperatively to correct a metabolic acidosis. The amount that will normalize blood pH can be approximated with the formula: Sodium bicarbonate (mEq) = 0.2 * patient weight (kg) * base deficit.

Answer 790

Amino acids that start with “L” are solely ketogenic: lysine and leucine.

Answer 791

Low molecular weight heparin (LMWH) more selectively inhibits activated factor X when compared to unfractionated heparin (UFH). LMWH, such as enoxaparin and dalteparin, work similarly to UFH by binding the serine protease inhibitor ATIII. Binding of ATIII by UFH or LMWH induces a conformational change that increases ATIII’s activity by 1000-fold to inhibit activated factor X and thrombin. LMWH BINDS UP LESS OF THROMBIN vs heparin

Answer 792

Direct thrombin inhibitors include argatroban, bivalirudin, lepirudin, and desirudin which are approved for use in HIT. Dabigatran is an oral direct thrombin inhibitor.

Answer 793

The solubility of gasses such as CO2 and O2 in liquids such as blood is affected by temperature. As temperature decreases, the solubility of these gasses is increased resulting in a decreased proportion of the gas in vapor form above the fluid and a decrease in partial pressure. As the blood gas analyzer increases the temperature of a sample of blood that is collected from a cooled patient, these gasses come out of solution and result in an increased measured PaCO2 and PaO2 compared to what is actually physiologically present in the patient. Because PaCO2 is increased in the warmed blood, measured pH values will be decreased in the warmed blood compared to the actual pH in the cooled patient. CO2 and O2 will be more soluble in cooled blood, resulting in a higher dissolved CO2 and O2 content in cooled blood and a lower content in warmed blood. pH teeters on CO2: Because CO2 is more soluble in cooled blood, less CO2 is available to participate in chemical reactions at cooler temperatures and thus the pH of cooled blood will be higher. Likewise, as blood warms, the more CO2 will be released from its dissolved state and result in a lower serum pH level.

Answer 794

In short, under alpha-stat management, the measurements that are generated by the analyzer following the warming of the patient sample to 37 °C are utilized to guide acid-base analysis, even though this will result in relatively alkalotic patient serum and low PaCO2 levels within the patient themselves. This management strategy has the benefit of maintaining cerebral autoregulation as the patient is experiencing a relative respiratory alkalosis given the relatively low PaCO2 levels. better in adults...pH-stat = Pediatric; alpha-stat = Adult

Answer 795

In pH-stat management strategies, the measurements are corrected for the patient's actual temperature before they are used for acid-base analysis. In these cases, PaCO2 (and therefore pH) will often be returned to normal normothermic values through the injection of CO2 to the bypass circuit oxygenator. This results in more cerebral vasodilation given the higher PaCO2 levels in the patient and has the theoretical benefit of allowing for more homogenous cerebral cooling in cases requiring deep hypothermic cardiac arrest. better in kids....pH-stat = Pediatric; alpha-stat = Adult

Answer 796

St. John's Wort has been used by patients for the treatment of depression and its mechanism of action is related to inhibition of serotonin reuptake, dopamine reuptake, and norepinephrine reuptake. Previous thoughts were that its action was similar to an MAO inhibitor, however the in vivo relevance of this has been invalidated. Primary surgical and anesthetic concerns include induction of CYP 3A4 resulting in enhanced metabolism of drugs such as lidocaine, alfentanil, and midazolam as well as CYP 2C9, which is involved in the breakdown of warfarin. Warfarin therapy is therefore unreliable in patients taking St. John's Wort and puts them at risk for DVT and thromboembolism. increased risk of organ rejection after trxplnt if on cyclosporine (p450)

Answer 797

Mivacurium is different from most NDNMBs because it is metabolized by pseudocholinesterase alone. ...still needs to be icnreased in burn patietns becuase of increased receptors

Answer 798

When a patient has a suspected infection, a rapid assessment for risk of sepsis can be made using the qSOFA score (at least 2 of the following: RR ≥ 22/min, altered mental status, or systolic blood pressure ≤ 100 mmHg).

Answer 799

Alfentanil has a more rapid onset of action due to its pKa of 6.5. The drug is able to rapidly cross the blood-brain barrier as it is highly lipid soluble and unionized (> 90%) at physiological pH of 7.4. Recall that small, lipophilic, unionized drugs are able to most rapidly cross phospholipid bilayers.

Answer 800

Hypovolemic (16%): hemorrhage. Cardiogenic (16%): acute myocardial infarction, end-stage cardiomyopathy, advanced valvular heart disease, cardiac arrhythmias, prolonged cardiopulmonary bypass, fulminant myocarditis, blunt myocardial trauma, medication induced (anthracycline toxicity). Obstructive (2%): pulmonary embolism, cardiac tamponade, tension pneumothorax, constrictive pericarditis, acute pulmonary hypertension, aortic dissection. Distributive (66%): severe sepsis, anaphylaxis, neurogenic (spinal shock), endocrinologic (adrenal crisis), toxic.

Answer 801

LBW Due to the concern of postoperative opioid-induced ventilatory depression in the obese patient, opioids are best based on lean body weight. Postoperative management in the obese population also warrants close respiratory monitoring of oxygenation and ventilation, as well as a multi-modal approach to analgesia.

Answer 802

A number of different strategies exist that can decrease a patient’s baseline risk for PONV. The six identified by the Society for Ambulatory Anesthesia include: 1) Avoid general anesthesia by utilizing regional anesthesia 2) Use propofol for induction and maintenance of anesthesia 3) Avoid nitrous oxide 4) Avoid volatile anesthetics 5) Minimize intra- and post-operative opioids 6) Adequately hydrate the patient

Answer 803

Simple febrile reactions to blood product administration are usually due to antibodies that the host has formed against HLAs present on donor leukocytes. The febrile period is usually mild, short-lived, and can be treated with acetaminophen.

Answer 804

Heart rate is the most important parameter regulating this relationship since decreasing heart rate will increase diastolic time allowing for decreased oxygen consumption and longer perfusion time for the coronary arteries

Answer 805

Changes that increase oxygen supply: - Increased hemoglobin concentration - Lower afterload and/or preload - Decreased contractility - Decreased heart rate Changes that decrease demand: - Decreased heart rate - Decreased afterload and/or preload - Decreased contractility

Answer 806

The following diagnoses should be considered in patients with a large R wave in lead V1: 1) Right ventricular hypertrophy 2) Posterior wall MI 3) Wolff-Parkinson-White syndrome 4) Muscular dystrophy 5) Right atrial enlargement 6) Right ventricular strain with ST-T wave abnormalities

Answer 807

Ways in which laminar flow will become turbulent include high gas flow rates, sharp angles within a tube, branch points within a tube, and an increase in the diameter of the tube. Increasing the density of gases flowing or decreasing viscosity also promotes turbulent flow Also, high density, large diameter and/or low viscosity

Answer 808

Reynolds number (R) = v * p * d / n = velocity * density * diameter / viscosity. The Reynolds number (R) is used to predict turbulent flow. When R < 2000, laminar flow is present. When R > 4000, turbulent flow is more likely. Resistance to flow increases when turbulent flow is present.

Answer 809

Anesthesia flowmeters use both density and viscosity to determine flow. Flowmeter tubes are tapered and calibrated for a specific gas. At the bottom of the tube, viscosity determines flow. Higher in the flowmeter, turbulent flow occurs because of increased velocity. When turbulent flow occurs, density is the major factor affecting flow. Additionally, increasing flow rates above a critical velocity will increase turbulent flow. Therefore, when anesthesia machine flow rates are increased turbulent flow is promoted.

Answer 810

The Haldane effect describes the relationship between the carbon dioxide dissociation curve in blood and oxyhemoglobin (HbO2). The CO2 dissociation curve, specifically, shifts to the right when the concentration of HbO2 increases in the blood The Haldane Effect describes the effect of oxygen on CO2 transport. The Haldane Effect (along with the Bohr Effect) facilitates the release of O2 at the tissues and the uptake of O2 at the lungs. This is represented by a right shift of the oxyhemoglobin dissociation curve and a left shift of the oxyhemoglobin dissociation curve respectively. The Haldane Effect results from the fact that deoxygenated hemoglobin has a higher affinity (~3.5 x) for CO2 than does oxyhemoglobin.

Answer 811

The Bohr effect describes the binding effect of H+ to Hb chains and the oxygen release and dissociation that occurs thereafter. Acidosis, for example, will shift the oxygen-hemoglobin dissociation curve toward the right, resulting in less attraction between Hb and O2. Ultimately, this will permit more CO2 to be transported from the tissue to the lungs during gas exchange. The curve will shift to the left for a low PCO2 and high pH.

Answer 812

Bernoulli’s equation is commonly used in echocardiography to assess the pressure gradient and area of mitral and aortic valves. It can be simplified by the equation pressure (P) = 4 * (velocity of blood)^2.

Answer 813

The diagnosis of FES using the Gurd criteria requires at least one major criterion (respiratory insufficiency, petechial rash, CNS involvement, and hypoxemia), at least four minor criteria (tachycardia, fever, unexplained drop in hematocrit or platelets, elevated erythrocyte sedimentation rate, retinal fat emboli, fat in urine, and fat in sputum) and the presence of fat macroglobulinemia.

Answer 814

Side effects of beta agonists include hypotension from blood vessel smooth muscle relaxation, tachycardia from β1 receptor activation, hyperglycemia, hypokalemia, and pulmonary edema. Terbutaline is a β2 receptor agonist used for bronchodilation. It is occasionally used, off-label from the FDA, to delay premature labor. Ritodrine is no longer FDA approved. Ritodrine and terbutaline are beta agonists selective for β2 > β1 receptors. β1 includes heart and adipose tissue. β2 effects include smooth muscle, adipose, liver, skeletal muscle, pancreas, and salivary glands. The smooth muscle relaxation produces the desired effect of uterine relaxation. The stimulation of adenylyl cyclase increases the conversion of ATP to cAMP. This decreases the available intracellular calcium and inhibits MLCK resulting in impaired contractility.

Answer 815

Available tocolytics include ethanol, magnesium sulfate, prostaglandin inhibitors, calcium channel blockers, and β-sympathomimetics.

Answer 816

SvO2 = SaO2 – VO2 / (1.34 * Hb * CO) therefore high CO= high mixed venous Mixed venous oxygen saturation (SvO2) is an indicator of global oxygen supply and demand balance. A low SvO2 indicates increased tissue oxygen extraction due to decreased oxygen supply relative to the demand. Septic shock and cyanide toxicity are conditions associated with normal or increased mixed venous oxygen saturation secondary to impaired tissue oxygen utilization.

Answer 817

Unstable narrow QRS complex supraventricular tachycardia should be treated as quickly as possible by synchronized cardioversion. If, however, the patient is hemodynamically stable, the situation may allow for attempts at terminating certain types of tachyarrhythmias pharmacologically with adenosine, which should be administered as a rapid IV push as close as possible to the heart. In contrast, wide complex ventricular tachyarrhythmias should be treated with unsynchronized defibrillation once the diagnosis is suspected or confirmed.

Answer 818

should be treated with unsynchronized defibrillation once the diagnosis is suspected or confirmed.

Answer 819

Unsynchronized defibrillation would be the appropriate response if the patient were found to be in pulseless ventricular tachycardia (VT) or ventricular fibrillation (VF), both of which are immediately life threatening non-perfusing rhythms. The ECG would show wide complex QRS which may be either monomorphic or polymorphic. Shock should be delivered within 3 minutes of arrest. Current guidelines suggest biphasic shock at 120-200 J. Each subsequent shock should increase the energy stepwise if the first one fails. In this particular answer choice, 200 J monophasic energy is below the recommended dose of 360 J for monophasic defibrillators. It is important to note that delivering an unsynchronized shock in this particular patient could lead to R-on-T phenomenon and actually result in pulseless VT or VF.

Answer 820

Kidney disease has several effects on the human body. Hyperkalemia and hypocalcemia are often seen, as well as anemia from decreased epoetin. Uremia can cause symptoms of anorexia, mental status changes, and platelet dysfunction.

Answer 821

Placental abruption typically presents with painful vaginal bleeding, uterine tenderness, and nonreassuring fetal heart rate patterns. Diagnosis is primarily clinical and ultrasonography is highly specific but not very sensitive. Risk factors include maternal hypertension, maternal cocaine and/or tobacco abuse (OR PATERNAL!!!), trauma, and advanced maternal age and parity.

Answer 822

Anterior mediastinal mass classically presents with orthopnea and widened mediastinum on chest radiography. It is imperative to avoid general anesthesia in these patients until further testing has been performed.

Answer 823

Prompt recognition, fluid resuscitation, respiratory support, and surgical stabilization of long bone fractures are required to reduce the morbidity and mortality associated with FES. Heparin, corticosteroids, and dextran have not been proven to be efficacious for treatment.

Answer 824

The Haldane effect explains the increased ability for hemoglobin to carry carbon dioxide (CO2) from the tissues to the lungs for exhalation (A). Deoxygenated hemoglobin has 3.5 times more capacity for CO2 than oxygenated hemoglobin. HalDANE--Delivery of Dioxode Stated another way: when hydrogen ions are in abundance the hemoglobin has less affinity for O2 (Bohr effect and occurs in tissue) and when oxygen is in abundance the CO2 has less affinity for hemoglobin (Haldane effect and occurs in lungs).

Answer 825

The increased delivery of O2 at the tissue level can be partly explained by the Bohr effect. The Bohr effect states that an increase in the CO2 and hydrogen ion concentrations will cause hemoglobin to have a decreased affinity for O2. This is seen as a rightward shift in the oxygen-hemoglobin dissociation curve. As a result, hemoglobin will release O2 to the tissues that are metabolically active and producing CO2. It is the complementary action to the Haldane effect. Whereas the Haldane effect explains increased binding of CO2 for delivery to the lungs, the Bohr effect explains decreased binding of O2 for delivery to the tissue. Stated another way: when hydrogen ions are in abundance the hemoglobin has less affinity for O2 (Bohr effect and occurs in tissue) and when oxygen is in abundance the CO2 has less affinity for hemoglobin (Haldane effect and occurs in lungs).

Answer 826

Heart rate generation in the cardiac transplant patient is dependent on the donor atrium. Resting intrinsic heart is elevated with reduced heart rate variability due to parasympathetic denervation. The Frank-Starling mechanism remains intact and the transplanted heart is heavily dependent on preload.

Answer 827

Hemodynamic effects of aortic cross clamping include: 1) Increased arterial blood pressure above the level of the clamp 2) Increased coronary artery blood flow 3) Increased left ventricular wall stress 4) Increased central venous pressure 5) Increased pulmonary artery wedge pressure 6) Decreased arterial blood pressure below the clamp 7) Decreased cardiac output 8) Decreased renal blood flow

Answer 828

Down syndrome consists of a myriad of congenital abnormalities that affect the anesthetic management of patients with the condition. Notably, the anesthetic provider should be prepared to manage atlantoaxial instability (AAI), macroglossia, OSA, subglottic stenosis, congenital heart defects, extremes of cardiac chronotropy, and intestinal malformations which may promote aspiration. Atlantoaxial instability (AAI) is another key feature of the disease. Care should be taken any time neck flexion or extension is required (as in tonsillectomy and adenoidectomy). There have been reports of subluxation after intubation and the child may require neck films if s/he is symptomatic.

Answer 829

Omphalocele lesions are more common than gastroschisis. Gastroschisis is typically an isolated lesion, involves exposed bowel without an enclosed covering through an abdominal wall defect, and has a higher incidence of heat loss, rapid dehydration, and infection. Omphalocele is an abdominal wall defect with a membranous covering and is often associated with other physical and chromosomal anomalies.

Answer 830

For non-intubated patients, enteric feeding (gastric or post-pyloric) should be stopped 8 hours prior to surgery to reduce the risk of aspiration. Post-pyloric feeding can decrease the risk of pneumonia, but it does not decrease the risk of aspiration. For intubated patients, enteric feeding can typically be continued through the perioperative period. Factors that increase the risk of aspiration in intubated patients receiving enteric feeding are the flat supine position, muscle relaxant use, and abdominal surgery.

Answer 831

Treatment of hypermagnesemia includes 1) stopping the source of magnesium, 2) antagonizing the effects of magnesium with calcium, and if moderate or severe 3) increasing elimination of magnesium with loop diuretics or possibly hemodialysis.

Answer 832

Magnesium potentiates nondepolarizing neuromuscular blocking drugs and local anesthetics and prolongs the duration of action of succinylcholine.

Answer 833

MELD: "I Crush Beer Daily" - INR, Creatinine, Bilirubin, Dialysis Child-Pugh: "Pour Another Beer At Eleven" - PT, Ascites, Bilirubin, Albumin, Encephalopathy

Answer 834

Risk factors for awareness under anesthesia include: substance abuse (opioids, benzodiazepines, cocaine), history of awareness, history of difficult intubation or anticipated difficult intubation, chronic pain patients using high doses of opioids, cesarean delivery, trauma and emergency surgery, use of neuromuscular blockade, total intravenous anesthesia, and limited hemodynamic reserve.

Answer 835

An R-on-T phenomenon occurs when a cardiac depolarization (R-wave) is initiated during a period of myocyte repolarization (T-wave) and can precipitate polymorphic ventricular tachycardia. Causes of R-on-T Phenomena include asynchronous cardiac pacing, long QT syndrome, or frequent PVC's.

Answer 836

middyastole

Answer 837

Opioid onset of action is related to unionized fraction (e.g. pKa) and lipid solubility. Opioid duration of action is related to lipid solubility, with low solubility leading to longer action. Alfentanil has rapid onset due to very high unionized fraction (low pKa) and moderate lipid solubility Remembering "4" will get you in the appropriate range for differences between alfentanil and fentanyl. Alfentanil has about 4 times faster onset. Alfentanil lasts about 1/4 the duration. Alfentanil is about 1/4 the potency (4x the dose of fentanyl)..

Answer 838

The right coronary artery (RCA) supplies the inferior and inferoseptal walls of the left ventricle The LCA provides blood supply to the apices of the LV and RV, the anterolateral LV, and the anterior two thirds of the interventricular septum. The RCA supplies the anterior and posterior RV, the RA, the upper atrial septum, the posterior third of the interventricular septum, and the inferior and posterior LV. Right-dominant hearts have an RCA which gives rise to the PDA and therefore supplies blood to the AV node but the PDA can arise from the LCx as well.

Answer 839

The endocrine catecholamines norepinephrine, epinephrine, and dopamine are synthesized by chromaffin cells within the adrenal medulla. The first step (also the rate-limiting step) in synthesis is the conversion of tyrosine to DOPA via the enzyme tyrosine hydroxylase. DOPA is also known as L-DOPA, levodopa, or L-3,4-dihydroxyphenylalanine. The next step is decarboxylation, which results in dopamine. Dopamine beta-hydroxylase then converts dopamine into norepinephrine. Epinephrine is produced when norepinephrine is methylated by phenylethanolamine N-methyltransferase (PNMT). The hormones produced in the adrenal medulla are released directly into the bloodstream, making the adrenal medulla an endocrine gland.

Answer 840

In general, volatile agents produce increases in CBF and ICP with reduction in CMRO2 when given at > 1.0 MAC.

Answer 841

MAC can be distinguished from moderate sedation in several ways. Likely most important is what was stated above, that providing sedatives for MAC may lead to changes in hemodynamic or respiratory parameters and the person administering MAC must be prepared and qualified to convert to general anesthesia. This is not true for moderate sedation since the primary goal of moderate sedation is to facilitate successful performance of the diagnostic or therapeutic procedure while providing patient comfort and cooperation. Additionally, since moderate sedation is not expected to induce depth of sedation that would impair airway (like MAC), a provider does not need to have rescue airway techniques. In the post-procedure period, MAC differs from moderate sedation in that it requires assuring a return to full consciousness, relief of pain, and the ability to manage physiologic responses or side effects from medications administered during the procedure.

Answer 842

Buprenorphine, a partial μ-receptor agonist, is a very effective agent at mitigating opioid withdrawal given its action at the μ-receptor itself. As a partial agonist, it has a ceiling effect for its analgesic and euphoric properties, as well for its respiratory depressive effects. It is often administered in combination with naloxone in an oral formulation to discourage its abuse.

Answer 843

Hypokalemia leads to characteristic ECG changes (QRS prolongation, ST-segment and T-wave depression, U-wave formation), muscle weakness, and decreased cardiac contractility. Perioperative management and decision to delay depends on the degree of hypokalemia, patient comorbidities, and the urgency of the procedure. In general, serum K+ < 2.5 mEq/L warrants delay of non-emergent surgery. Serum levels between 2.5 - 3.0 mEq/L warrants delay of elective (non-emergent or non-urgent) procedures until the cause of hypokalemia is identified and corrected.

Answer 844

The sacrococcygeal ligament covers the opening of the sacral hiatus. Landmarks for caudal blockade include the triangle with vertices at the posterior superior iliac spines and the sacral hiatus. The sacral hiatus lies directly superior to the coccyx bone. The sacral hiatus is created by the non-union of the S4 and S5 lamina. In infants, the dural sac extends to S3/S4 and makes dural puncture more likely. In adults, the sacrococcygeal ligament becomes heavily calcified making caudal anesthesia difficult.

Answer 845

Apnea of prematurity can be seen following surgery and is defined by episodes of apnea and bradycardia. The etiology may include a decreased ventilatory control, anemia, respiratory muscle fatigue, and hypothermia. Risk factors include prematurity, congenital anomalies, chronic lung disease and history of apnea and bradycardia. The treatment includes tactile stimulation and possibly prolonged ventilatory support. Those with a history of apnea and bradycardia may be prophylactically treated with caffeine or theophylline to increase the central respiratory drive prior to surgery.

Answer 846

Emergence delirium is a state of extreme excitement that occurs more frequently in children between the ages of 1 to 4. It can also occur in older children, adolescents, and adults. Emergence delirium generally lasts less than 30 minutes and treatment is supportive. Use of less soluble volatile anesthetics (e.g. desflurane, sevoflurane) is strongly associated with the development.

Answer 847

Specific donor management goals (DMGs) vary by study and by center. Most agree on general principles such as maintenance of MAP > 60 mm Hg, avoidance of hypernatremia > 155 mmol/L, limiting vasopressors, avoiding extremes of serum pH, avoiding hyperglycemia, and maintenance of urine output. The specifics of the goals can vary; for example, one study describes minimum urine output as 0.5 mL/kg/h while another notes 1.0 mL/kg/h. After brain death, the anterior and posterior pituitary fail causing a dramatic fall in T3 and T4 concentrations

Answer 848

There is an increased risk of severe hyperkalemia in hypovolemic patients with severe metabolic acidosis. The increased K+ in the metabolic acidosis is linked to the gastrointestinal tract rather than skeletal muscle. Management of in severe hyperkalemia associated with severe metabolic acidosis. * Hyperventilation * 1-2 mg IV CaCl * 1 mEq/kg NaHCO3 * 10 units regular insulin in 50 mL of 50% glucose

Answer 849

Conditions which down-regulate nAChRs include: Myasthenia gravis, anticholinesterase poisoning, and organophosphate poisoning. The opposite is true for these conditions, in that they are less sensitive to succinylcholine and more sensitive to nondepolarizing neuromuscular blockers.

Answer 850

These conditions include spinal cord injury, stroke, burns, prolonged immobility, prolonged exposure to neuromuscular blocking agents, multiple sclerosis, and Guillain-Barré syndrome. All of these conditions will have an exaggerated response to succinylcholine, a depolarizing neuromuscular blocker, leading to elevated potassium levels to the point of ventricular tachycardia, fibrillation, and cardiac arrest. These conditions which upregulate nAChRs are also more resistant to nondepolarizing neuromuscular blockers.

Answer 851

Thermogenesis in the infant occurs by catabolism of “brown” fat. This is a specialized type of adipose tissue located in the posterior neck, interscapular region, vertebral areas, and around the kidneys and adrenal glands.

Answer 852

Initially, heat loss after the induction of GA is primarily from redistribution of core heat to the peripheral tissues (limbs, skin, skeletal muscles, etc.). This decline begins almost immediately after induction (Phase I) and continues throughout the first few hours of GA. Then, a thermal balancing occurs (Phase II), and finally the temperature decline levels (Phase III) or begins to rise with active warming. After redistribution of heat has occurred, it is much more difficult for the child to keep that heat in the body. Children lose heat to the environment at a faster pace than adults due to their minimal subcutaneous fat, poor ability to efficiently generate heat, and their relatively LARGE body surface area to volume ratio.

Answer 853

Children lose heat to the environment at a faster pace than adults due to their minimal subcutaneous fat, poor ability to efficiently generate heat, and their relatively LARGE body surface area to volume ratio.

Answer 854

Radiation accounts for the greatest loss of heat. Hypothermia leads to norepinephrine secretion, pulmonary hypertension, lactic acidosis, and worsening hypoxia.

Answer 855

A deep cervical plexus block is a paravertebral block of spinal nerves C2-C4 as they emerge from their foramina, therefore depositing local anesthetic near various neural and vascular structures. Complications and side effects include intravascular injection, blockage of the phrenic and superior laryngeal nerve, and spread of the local anesthetic into epidural and subarachnoid spaces. Because of the risk of phrenic nerve blockage and diaphragmatic paresis, deep cervical plexus blocks are relatively contraindicated in patients with existing phrenic nerve palsy (especially if on the contralateral side) and significant pulmonary compromise.

Answer 856

Anatomic landmarks of the deep cervical plexus block include the mastoid process, Chassaignac tubercle (transverse process of C6), and posterior border of the sternocleidomastoid muscle (which overlies the plexus). A line is drawn from the mastoid process to the palpated Chassaignac tubercle, and the insertion sites for C2, C3, and C4 are marked along that line in 2 cm increments.

Answer 857

After smoking cessation, carbon monoxide levels normalize after 12-24 hours, - mucociliary function begin to normalize after 2-3 weeks, - and the risk of postoperative pulmonary complications drastically decreases after 8 weeks.

Answer 858

The primary method of increasing oxygen delivery to the body at high altitude is an increased minute ventilation as a result of hypoxic stimulation of peripheral chemoreceptors. Initially, this causes a respiratory alkalosis, however, after a few days the body compensates by increasing the bicarbonate loss in the kidneys. This helps normalize the body's pH, but the PaCO2 remains low. The increase in minute ventilation does not change with time. The minute ventilation remains elevated as long as the person remains at altitude. During this time the respiratory rate increases but the vital capacity and functional residual capacity remain the same. Another major effect of chronic hypoxia is an increase in pulmonary vascular resistance secondary to hypoxic pulmonary vasoconstriction. This results in increased right-sided heart pressures.

Answer 859

Resuscitation of the unresponsive drowning victim begins with rescue breaths.

Answer 860

Hyperthyroidism results from increased secretion of thyroid hormones. The most common cause is Graves disease with thyroid adenoma, toxic multinodular goiter, and thyroiditis being other causes. Laboratory studies will show an elevated T3 and T4 and low/normal TSH.

Answer 861

Excessive thyroid hormones cause a variety of symptoms depending on the body system: General: weight loss, heat intolerance and warm, moist skin Cardiovascular: tachycardia, atrial fibrillation and congestive heart failure Neurologic: nervousness, tremor, hyperactive reflexes Gastrointestinal: diarrhea Musculoskeletal: muscle weakness Hematologic: anemia, thrombocytopenia

Answer 862

Propofol does not decrease hepatic blood flow and, in fact, may increase hepatic blood flow due to splanchnic vasodilation. It has not been shown in clinical practice to precipitate episodes of hepatic encephalopathy.

Answer 863

Respiratory alkalosis can be a result of central causes that increase respiratory drive like: stroke, aspirin overdose, anxiety, pain, and progesterone. Additionally, there are several pulmonary causes of respiratory alkalosis which include pulmonary embolism, pneumonia, or asthma. Respiratory alkalosis also has significant metabolic effects which include hypocalcemia, hypokalemia, and hypophosphatemia.

Answer 864

There are very few medications that may need to be stopped in the perioperative period. It is important that the physician consider the implications, both anesthesia, and long-term, of stopping these medications. The most recognized medication class that should be routinely stopped is diuretics. Others that may be considered are ACE-Is and ARBs.

Answer 865

Tricyclic antidepressants (amitriptyline, nortriptyline, dosulepin) – act by preventing presynaptic reuptake of norepinephrine and serotonin. They also have anti-muscarinic, anti-histaminergic and anti-alpha-1-adrenergic effects. These medications may cause sedation and reduction of the seizure threshold. Anti-cholinergic side effects may be bothersome to some patients (QRS widening with QT prolongation, postural hypotension). The most significant anesthetic-related concern is the potentiation of the effects of indirectly acting sympathomimetics (ephedrine). Abrupt cessation may cause cholinergic symptoms and worsening of psychiatric disease.

Answer 866

Monoamine oxidase inhibitors – acts by inhibiting monoamine oxidases, enzymes involved in the breakdown of amine neurotransmitters (serotonin and norepinephrine). This results in an increase in transmitters. There are two classes – irreversible inhibitors (phenelzine, tranylcypromine, and isocarboxazid) and reversible inhibitors (moclobemide). In patients on MAO-Is, a profound pressor effect may occur after administration of both indirect and direct acting sympathomimetics. Thus when necessary, direct sympathomimetics are preferred, but there still needs to be cautious as severe hypertension can occur. Meperidine may precipitate serotonergic crises in patients taking MAO-Is and thus should be avoided. The Libby Zion Law was created in response to this specific negative interaction.

Answer 867

Nausea and vomiting occur after spinal anesthesia approximately 20% of the time (D). Risk factors include high block (above T5), hypotension, opioid administration, and a history of motion sickness. Unopposed parasympathetic (vagal) activity after sympathetic blockade causes increased peristalsis of the gastrointestinal tract, which can lead to nausea. For this reason, atropine is nearly universally effective in treating nausea associated with neuraxial blockade. Glycopyrrolate is also an effective option, particularly when atropine would be less desirable.

Answer 868

Decreased atmospheric pressure will result in increased vaporizer output. Of note, the partial pressure will remain the same according to the Dalton Law. Modern vaporizers are temperature-compensated variable-bypass agent-specific vaporizers. The splitting ratio is calibrated for each agent based on vapor pressure. These agents can compensate for significant changes in room temperature, without having significant changes in vaporizer output. Increasing fresh gas flow and decreasing barometric pressure will increase the output of the vaporizer.

Answer 869

Ischemic optic neuropathy presents as sudden onset, painless vision loss most typically following lengthy spine surgeries in the prone position. Other risk factors include male sex, large blood loss, anemia, large crystalloid fluid resuscitation, hypotension, and possibly increased IOP or orbital venous pressure.

Answer 870

A carbohydrate load can precipitate an attack in a patient with hypokalemic periodic paralysis. The carbohydrates are broken into sugars which stimulate the pancreas to secrete insulin. Insulin increases the activity of the sodium/potassium ATPase which pumps potassium from the serum into cells. This effectively lowers the serum potassium level. The decreased serum potassium level can precipitate an attack.

Answer 871

acetazolamide (carb-anhydrase inhibitor...MOA unclear) | potassium sparking duretics

Answer 872

Warfarin Reversal, Urgent Surgery: INR 1.5 - 1.9: consider PCC, FFP may not be useful INR 1.9 - 5: PCC or FFP + 1-3 mg of IV vitamin K INR 5 - 9: PCC or FFP + 2-5 mg IV vitamin K

Answer 873

Warfarin Reversal, Surgery 24-48 Hours Later: INR 1.5 - 1.9: 1 mg PO vitamin K INR 1.9 - 5: 1 - 2.5 mg PO vitamin K, if INR still elevated 24 hours after dose give 1 - 2 mg PO vitamin K INR 5 - 9: 2.5 - 5 mg PO vitamin K, if INR still elevated 24 hours after dose give 1 - 2 mg PO vitamin K

Answer 874

Nasogastric tubes and larger bore tubes are associated with increased risk of otitis media and sinusitis when used for a long time. Placing a gastric tube beyond the pyloric junction has not been shown to reduce the risk of pulmonary aspiration.

Answer 875

awake intubation for their procedures.

Answer 876

patient undergoes multiple cardiovascular and autonomic nervous system changes during and shortly after ECT. Initially following seizure activity there is an increase in parasympathetic stimulation, which can manifest as increased secretions, bradycardia, and transient asystole. To counteract these effects, atropine may be given as premedication or during induction for ECT. The increased parasympathetic activity is quickly followed by an increase in sympathetic stimulation (catecholamines), which tends to last for several minutes. The large sympathetic discharge can cause hypertension and tachycardia. Occasionally, T-wave inversion or ST depression can be seen briefly in response to this sympathetic discharge. These changes are usually transient and rarely need treatment.

Answer 877

Postpartum hemorrhage is blood loss greater than 500 mL with vaginal delivery or greater than 1000 mL with cesarean section. The most common cause of early postpartum hemorrhage (accounting for 80-90% of incidences) is uterine atony, or diminished myometrial contractility. Normally, postpartum uterine contraction allows for compression of intrauterine vessels that were delivering to the placenta. Risk factors for uterine atony include multiparity, multiple gestations, polyhydramnios, chorioamnionitis, prolonged labor, oxytocin-induced labor, and mechanical factors such as clot or retained products.

Answer 878

Video laryngoscopy has been shown to improve glottic visualization but not necessarily improve intubation success. It has also been associated with an increased rate of life-threatening complications including death, cardiac arrest, cardiovascular collapse (SBP < 90 mmHg), hypoxemia (SpO2 < 90%), severe hypoxemia (SpO2 < 80%), and arrhythmia (VT, VF, PVCs).

Answer 879

Administration of 2-chloroprocaine may decrease the efficacy of subsequently administered neuraxial drugs including bupivacaine, morphine, and fentanyl. Chloroaminobenzoic acid (the metabolite of 2-chloroprocaine) may be responsible for decreasing the efficacy of subsequent bupivacaine administration. Chloroaminobenzoic acid may also act as an antagonist of the µ-opioid receptor, leading to reduced efficacy of subsequent opioid neuraxial administration.

Answer 880

SvO2 = SaO2 - [VO2 ÷ (CO * Hb * 1.36)], therefore: SvO2 is increased in the setting of decreased VO2 (e.g. sepsis, cyanide toxicity, hypothermia), increased SaO2, increased CO (e.g. hyperdynamic circulation, arteriovenous fistulas), and increased Hb (e.g. polycythemia). SvO2 is decreased in the setting of reduced SaO2 (e.g. methemoglobinemia), decreased CO (e.g. cardiogenic shock), and decreased Hb (e.g. anemia) as well as increased VO2 (e.g. fever, shivering, stress response).

Answer 881

Methemoglobinemia will cause SpO2 to overestimate SaO2 values (due to the left shift of the oxyhemoglobin dissociation curve) and will characteristically have a pulse oximeter reading of 80-85% if the methemoglobinemia level if high enough. Methemoglobinemia causes a change in the iron in hemoglobin from the ferrous (2+) to the ferric (3+) form. This impairs the ability of hemoglobin to bind oxygen and causes it to hold onto its remaining oxygen more tightly causing a left shift in the oxyhemoglobin dissociation curve. Together, these changes lead to both decreased arterial oxygen saturation (SaO2) and functional anemia.

Answer 882

Sympathetic drugs have effects across multiple organ systems and can cause metabolic effects including hyperglycemia, increased free fatty acids, and hypokalemia through alpha- and beta-receptor activation.

Answer 883

The blood supply to the AV node is supplied by the right coronary artery (RCA) in approximately most of the population (80%). The blood supply to the AV node is supplied the left circumflex artery (LCX) in approximately 20% of the population.

Answer 884

The blood supply to the SA node, however, is not influenced by "coronary dominance". In approximately 55-65% of the population the SA node is supplied by the RCA, and by LCX in the remainder of the population. Similar to the AV node, it is possible to have a dual blood supply of the SA node in a small portion of the population.

Answer 885

Ischemia of the PDA as opposed to the LAD or LCX (in a right dominant circulation) is more likely to cause mitral regurgitation secondary to dysfunction of the posteromedial papillary muscle. This is because the anterolateral papillary muscle has a dual blood supply (LAD + LCX) and the posteromedial papillary muscle relies on the PDA for blood supply.

Answer 886

Right dominance (RCA gives off PDA): 80% of population. Left dominance (LCX gives off PDA): 20% of population. AV node blood supply (influenced by dominance): RCA 80%, LCX 20%. SA node blood supply: RCA 55%, LCX 45%.

Answer 887

Respiratory Changes During Pregnancy ERV -25% IRV +5% RV -15% TV +45% FRC -20% IC +15% TLC -5% ***VC unchanged AV +45% DS +45% MV +45% ****RR unchanged

Answer 888

VACTERL association stands for vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities. Infants often require multiple surgical procedures for correction of structural anomalies and if neural tube defects are present, caudal anesthesia is contraindicated for correction of imperforate anus. An infant with tracheoesophageal fistula and esophageal atresia may also have coarctation of the aorta.

Answer 889

Because mannitol can cause rapid expansion of a patient’s intravascular fluid volume, it should be used with care or avoided completely in patients with congestive heart failure.

Answer 890

Factor VIII can be used to help determine the underlying etiology of coagulation abnormalities in patients with liver disease. In coagulation disorders mostly attributable to DIC, factor VIII will be decreased. Coagulopathy due to end-stage liver disease without concomitant DIC will show a normal or elevated factor VIII level.

Answer 891

large bronchiles The large airways of the upper bronchi provide approximately 80% of the resistance to gas flow during negative pressure ventilation. This is due to their propensity towards turbulent flow (large diameter, irregular shape, branching nature), as well as the smaller cross-sectional area than the total area for airflow provided by the terminal bronchioles.

Answer 892

Large volumes and rapid administration of normal saline can produce a non-anion gap hyperchloremic metabolic acidosis. Associated laboratory values include decreased plasma HCO3-, increased plasma Cl-, decreased SID, and a normal anion gap.

Answer 893

Acetazolamide is a potent inhibitor of carbonic anhydrase, which results in wasting of sodium and bicarbonate in the proximal tubule, with subsequent diuresis and also alkalinization of the urine. This results in a hyperchloremic metabolic acidosis.

Answer 894

Leftward shift of oxyhemoglobin dissociation curve is a feature of alpha-stat ABG. Alpha-stat allows for pH to rise naturally with cooling. At 20 ºC the pH is 7.70 and at 37 ºC it is 7.4. In alpha-stat, PaCO2 is maintained at 40 mmHg at 37 ºC and is not corrected for patient body temperature.

Answer 895

Myasthenic syndrome is associated with small cell carcinoma of the lung. Patients commonly have proximal limb weakness, improvement in strength with exercise, and sensitivity to succinylcholine. Myasthenia gravis patients display fatigue with exercise, are resistant to succinylcholine, and have extraocular, bulbar, and facial muscle weakness. Refer to the above table for additional key differences. TrueLearn Insight : "Lambs are sensitive animals", Lambert-Eaton is sensitive to both types of relaxants.

Answer 896

Succinylcholine apnea in a patient with abnormal pseudocholinesterase can potentially be reversed with low dose neostigmine (< 0.03 mg/kg) after a phase II block occurs. However, the safest course of action is generally continuation of mechanical ventilation until adequate muscle tone returns. Further, giving neostigmine in this scenario could potentially prolong the blockade.

Answer 897

Patients with panhypopituitarism due to a pituitary tumor are generally prescribed thyroxine, glucocorticoids, and vasopressin pre-operatively. A patient with a pituitary prolactinoma is likely to be taking cabergoline or bromocriptine, both of which are dopamine agonists.

Answer 898

Patients with acromegaly may present for transsphenoidal resection of the pituitary gland due to a GH-secreting tumor. These patients should be treated as difficult airways as a result of a reduction in size of the glottic opening, hypertrophy of aryepiglottic folds, calcinosis of the larynx, recurrent laryngeal nerve injury, and hypertrophy of the tongue.

Answer 899

Intercostal blocks are associated with the highest plasma levels of local anesthetic following completion due to the high vascularity of the area. Plasma local anesthetic concentrations following regional techniques, from highest to lowest, are: intravenous > intercostal blocks > caudal > epidural > brachial plexus > intravenous regional > lower extremity blockade. TrueLearn Insight : Mnemonic - IICEBALLS: intravenous > intercostal > caudal > epidural > brachial plexus > axillary > lower limb > subcutaneous

Answer 900

Propofol infusion syndrome is associated with rhabdomyolysis, lactic acidosis, renal failure, and cardiac failure. The maximum recommended dose is 4 mg/kg/hr, however, propofol is not recommended for use in children for prolonged sedation.

Answer 901

The correct precurarization dosage for any nondepolarizing agent prior to succinylcholine administration is 10% of the ED95 dose. For rocuronium, this would be 0.03 mg/kg.

Answer 902

The ED95 for nondepolarizing neuromuscular blocking drugs is the dose that causes 95% twitch suppression in 50% of the population.

Answer 903

In a patient with known sepsis, septic shock can be clinically diagnosed by the combination of a vasopressor requirement necessary to maintain a mean arterial pressure > 65 mmHg and a lactate > 2 mmol/L despite adequate volume resuscitation. Sepsis is defined as “life-threatening organ dysfunction caused by a dysregulated host response to infection," where organ dysfunction is judged by the patient's SOFA score. SIRS criteria are no longer used to diagnose sepsis or septic shoc

Answer 904

Positive pressure ventilation can cause oliguria due to downstream effects of increased intrathoracic pressure. These include: impaired renal perfusion and renal venous drainage, decreased preload and increased right ventricular afterload, stimulation of the sympathetic nervous system, and release of inflammatory cytokines.

Answer 905

Absolute contraindications to ECT include pheochromocytoma, recent stroke, recent intracranial surgery, intracranial mass lesion, recent MI, and unstable cervical spine.

Answer 906

The response to bronchodilators as seen on PFTs follows a bell-shaped curve; patients with moderate COPD will benefit most while patients with mild or severe COPD benefit least. If PFTs reveal pneumonectomy may not be tolerated, split-function lung testing using xenon radiospirometry and technetium imaging is the recommended next step in preoperative workup.

Answer 907

Central diabetes insipidus occurs due to failure of the pituitary to secrete antidiuretic hormone resulting in a high output of poorly concentrated urine, hypernatremia and polydipsia. It can become so severe that it is life-threatening thus treatment should be instituted quickly with free water replacement and possibly DDAVP. Central diabetes insipidus can be differentiated from nephrogenic diabetes insipidus based on responsiveness to DDAVP.

Answer 908

Myofascial pain syndrome is best treated with trigger point injection, physical therapy, and transcutaneous electrical nerve stimulation.

Answer 909

Methemoglobinemia occurs when hemoglobin becomes oxidized from Fe2+ to Fe3+. Methemoglobin is unable to bind oxygen and causes a functional anemia, in addition to left shifting the oxygen dissociation curve. Methemoglobin has an absorbance of 630 nm, which correlates to an oxygen saturation of 84-86% on pulse oximetry. Co-oximetry should be used to aid in the diagnosis and treatment of methemoglobinemia. If unavailable, blood can be sent for a methemoglobin level. Ascorbic acid also known as vitamin C, functions as an electron receptor and aids in the reduction of Fe3+ to Fe2+. Ascorbic acid functions to reduce hemoglobin slower than methylene blue does. However, ascorbic acid does not have the hemolytic effect that methylene blue does in a G6PD deficient patient.

Answer 910

Amyl nitrite is used to treat cyanide toxicity. Amyl nitrate oxidizes Fe2+ to Fe3+. Cyanide binds to methemoglobin more actively than it binds to normal hemoglobin. Thus, by inducing a low-level of methemoglobinemia the methemoglobin in turn can sequester cyanide as cyanmethemoglobin.

Answer 911

Methylene blue is often the drug of choice when treating methemoglobinemia. Methylene blue provides an electron receptor for the reduction of methemoglobin using NADPH produced from the hexose phosphate pathway. In a patient with G6PD deficiency the hexose phosphate pathway is dysfunctional and free radicals develop, which causes red blood cell lysis. Therefore, methylene blue should be avoided in patients with G6PD deficiency. Additionally, methylene blue is a potent reversible monoamine oxidase inhibitor (MAOI) and may interact with serotonergic psychiatric medications leading to life-threatening serotonin syndrome.

Answer 912

The use of high-frequency oscillatory ventilation is associated with reduced risk of barotrauma and is one of many ventilator modes, along with permissive hypercapnia strategies and intratracheal pulmonary ventilation (ITPV), that has been successfully used. The ventilation goals in these cases include low tidal volumes and the minimizing peak pressures.

Answer 913

A patient with hypertension and organ dysfunction can be classified as having preeclampsia. Hypertension is defined as a blood pressure of greater than 140/90 mmHg on two separate occasions at least 4 hours apart. End organ dysfunction is defined as any of the following: - Proteinuria (1+ dipstick, 0.3mg/dL urine protein/creatinine ratio, or 300 mg in 24 hour urine collection) - New-onset thrombocytopenia (< 100,000/mL) - New-onset renal dysfunction of elevated creatinine (1.1 mg/dL or two times baseline) - New-onset visual disturbance or cerebral symptoms - Pulmonary edema - Liver dysfunction (AST and ALT two times the upper limit of normal)

Answer 914

Pre-eclampsia is a syndrome of pregnancy that occurs after 20 weeks gestation. Pre-eclampsia is likely due to an abnormal placenta with vascular hyperreactivity. This hyperreactivity is likely a result of an imbalance of thromboxane A2 and prostacyclin PGI2. As a result, uterine and renal blood flow decreases. Systemic vascular resistance (SVR) increases while intravascular volume decreases.

Answer 915

The ratio of the fractional concentration of alveolar anesthetic to inspired anesthetic (FA/FI) is a measure of anesthetic uptake and speed of induction. There are a variety of factors that speed uptake of inhaled anesthetics, including low blood:gas solubility (KB:G), low CO, high MV, high delivered concentration, and low time constant (low circuit volume / high fresh gas flow).

Answer 916

Iso> sevo> des

Answer 917

Hemolytic transfusion reactions can be defined as acute or delayed. Both are the result of recipient antibody and complement attack on donor cells. Acute hemolytic transfusion reactions are almost always due to ABO incompatibility and DHTRs are typically secondary to antibodies associated with the Rh, Kidd, or Kell systems.

Answer 918

Midazolam bioavailability among routes of administration (greatest to least): intravenous > intramuscular > intranasal > rectal > oral. Oral bioavailability is highly dependent on dose; bioavailability is lower with higher doses. This means that rectal bioavailability could potentially be lower than oral, but again it is dose dependent.

Answer 919

Four main factors promote faster inhalational induction in infants and children compared to adults by allowing a more rapid rise in FA:FI: 1. Increased minute ventilation relative to FRC (most important) 2. Increased blood flow to vessel-rich organs 3. Decreased blood:gas partition coefficients 4. Decreased tissue:blood partition coefficients

Answer 920

Lithium prolongs action of succinylcholine and non-depolarizing relaxants such as rocuronium and vecuronium Lithium may decrease anesthetic requirements (lower MAC) because it blocks brainstem release of norepinephrine, epinephrine, and dopamine.

Answer 921

nitroglycerin causes systemic venodilation by conversion to nitric oxide in the vascular smooth muscle, decreasing preload. It relaxes smooth muscle in a dose-dependent manner, dilation of both arterial and venous systems. Its onset of action is rapid, 1 to 3 minutes, and the duration of action is 3 to 5 minutes.

Answer 922

Key signs of aspirin or salicylate toxicity include tinnitus, altered mental status, and tachypnea. Arterial blood gas generally shows a mixed respiratory alkalosis and metabolic acidosis. Initial treatment includes supportive measures, gastric lavage, and activated charcoal. Additional measures include bicarbonate administration to reduce systemic acidosis and to alkalinize urine for increased aspirin clearance. Hemodialysis should be considered in severe toxicity cases.

Answer 923

Ketamine may induce seizures, especially in patients with lower seizure threshold. Cerebral metabolic rate and cerebral blood flow increase with ketamine administration. Treatment for status epilepticus includes: First Line: benzodiazepines. Second Line: fosphenytoin, phenytoin, valproic acid, or levetiracetam. Third Line: propofol or phenobarbital.

Answer 924

All antithrombotic agents are associated with independent non-bleeding side effects. Heparin is potentially associated with thrombocytopenia, osteoporosis, and hypoaldosteronism. Warfarin is associated with skin necrosis and all of the novel oral anticoagulants are commonly associated with gastrointestinal upset.

Answer 925

Absolute contraindications to neuraxial anesthesia include patient refusal, the inability to remain still during placement, and raised intracranial pressure. Relative contraindications include coagulopathy, hypovolemia, skin infection in the area of injection, and a lack of an experienced anesthesiologist.

Answer 926

Patients with pyloric stenosis often develop a hyponatremic hypokalemic hypochloremic metabolic alkalosis. Normalization of chloride is probably the best indicator that metabolic alkalosis has resolved in these patients.

Answer 927

epidurals are OK Patients with MS are susceptible to an exacerbation of their symptoms in the perioperative period caused by surgery and the use of general or spinal anesthesia. Succinylcholine should be used cautiously or avoided. Extended postoperative care may be required with emphasis on managing respiratory insufficiency. TrueLearn Insight : Hyperthermia may result in MS symptom exacerbations. Special care should be taken perioperatively to ensure normothermia.

Answer 928

When renal blood flow (RBF) decreases from a variety of factors, the concurrent decrease in glomerular filtration rate (GFR) leads to a decrease in the amount of chloride that is sensed at the juxtaglomerular (JG) apparatus. When there is decreased chloride concentration at the JG apparatus, the afferent arterioles dilate and increase glomerular flow and GFR. In addition, the decreased chloride concentration leads to the release of renin from the JG apparatus, ultimately causing vasoconstriction of the efferent arterioles by angiotensin II.

Answer 929

Adenosine will terminate SVTs caused by a reentrant circuit involving the AV node (i.e., AVNRT, AVRT). Frequently, atrial tachycardia will also terminate. Adenosine will slow the ventricular rate in atrial fibrillation and atrial flutter, but it is very unlikely the tachyarrhythmia will terminate.

Answer 930

Increased minute ventilation in pregnancy leads to a respiratory alkalosis with a compensatory metabolic acidosis (pH may remain normal or be slightly elevated). Increased alveolar ventilation also leads to an increase in PaO2.

Answer 931

Factors that cause a leftward shift of the carbon dioxide-ventilatory response curve include, but are not limited to: pregnancy, arterial hypoxemia, acidosis, increased intracranial pressure, and pain or surgical stimulus. Note that these are not the same as factors that shift the hemoglobin-oxygen dissociation curve (e.g. acidosis in particular).

Answer 932

A right-to-left intracardiac shunt slows the rate of inhalational induction of anesthesia since the shunted blood is not involved in gas exchange within the alveoli. Conversely, a right-to-left shunt speeds the rate of IV induction because a portion of the drug bypasses the lungs, directly enters the left side of the heart and is quickly delivered to brain tissue.

Answer 933

Desflurane Nitrous Oxide Sevoflurane Isoflurane Halothane 0.42 0.46 0.69 1.46 2.54

Answer 934

Reduced cardiac output promotes a faster rate of inhalation induction. This phenomenon is especially true with volatile agents readily soluble in blood. (ISO)

Answer 935

Factors leading to increased compound A include (1) low fresh gas flows or closed circuit, (2) Baralyme > soda lime >> calcium hydroxide lime, (3) higher concentration of sevoflurane, (4) high absorbent temperature, (5) fresh absorbent. Interestingly, dehydration of Baralyme increased the concentration of compound A but dehydration of soda lime decreased the concentration of compound A. Ethyl violet is the pH indicator within carbon dioxide absorbents.

Answer 936

The Bowditch effect refers to when there is an increase in contractility due to an increase in heart rate. In hypertrophic obstructive cardiomyopathy (HOCM), the goal is to keep contractility low. Avoiding increases in heart rate will keep contractility from increasing (Bowditch effect).

Answer 937

Periodic recruitment maneuvers (or "sighs") during mechanical ventilation have been shown to transiently improve oxygenation, though this effect is short-lived. No long-term mortality benefit has been shown from the routine use of periodic recruitment maneuvers. Conclusions from the ARDSnet ALVEOLI trial recommend against the routine use of a periodic sigh during mechanical ventilation of patients with acute respiratory distress syndrome.

Answer 938

Masseter muscle spasm, tachycardia, tachypnea, and increased ETCO2 are early warning signs of an impending MH episode in susceptible individuals.

Answer 939

Malignant Hyperthermia (MH) is a life-threatening condition caused by an induced hypermetabolic state of skeletal muscle. Susceptibility to MH is typically genetic and follows an autosomal dominant inheritance pattern with variable penetrance. Mutations lead to abnormally configured ryanodine calcium channels in the skeletal muscle sarcoplasmic reticulum. When activated by certain triggers (volatile anesthetics, succinylcholine), the mutated calcium channels change into a configuration that remains stuck open, resulting in excess myoplasmic calcium. This calcium ion load leads to excess oxygen consumption and ATP utilization which in turn leads to increased CO2 production, ATP depletion, and lactate production. If left uncontrolled, MH can lead to rhabdomyolysis and myonecrosis, renal failure, hyperkalemia, arrhythmias, DIC, and ultimately death.

Answer 940

The initial compensatory mechanism for anemia is a rightward shift in the oxygen-hemoglobin dissociation curve, resulting in more off-loading of oxygen to tissues. This is followed by redistribution of blood to vital organs.

Answer 941

Angiotensin converting enzyme catalyzes the degradation of bradykinin. Under normal conditions, bradykinin promotes vasodilation by increasing production of arachidonic acid metabolites and nitric oxide. ACE inhibition will increase levels of bradykinin, promoting its effect in reducing blood pressure. Angiotensin converting enzyme (ACE) inhibitors are a class of drugs developed for the treatment of hypertension. They work by inhibiting the vasoconstrictive and sodium-retentive properties of angiotensin II (ATII) and promoting the vasodilatory and natriuretic properties of bradykinin. Specifically, ACE inhibitors decrease the formation of ATII and decrease the degradation of bradykinin.

Answer 942

In cardiac tamponade, keep it “fast, full, and tight.” Cardiac output is heart rate dependent (“fast”), stroke volume is fixed and dependent on adequate preload (“full”), and the vascular tone should be (“tight”). Transesophageal echocardiography is the best diagnostic tool for detecting a pericardial fluid collection.

Answer 943

Cyanide toxicity can occur with the use of sodium nitroprusside. Sodium nitroprusside is used as a vasodilator, however its metabolism results in the release of cyanide ions. Usually the cyanide ions are metabolized and no side effects occur. When higher doses of nitroprusside are used for prolonged periods of time, cyanide can build up and toxicity occurs. Cyanide toxicity is characterized by metabolic acidosis and cardiac arrhythmias. Treatment is with hydroxocobalamin.

Answer 944

Propofol acts on GABAA receptors. Propofol increases the time that the GABAA receptors remain open after activation. GABAA receptors, when active, allow Cl- to enter neurons and hyperpolarize the cell. Propofol is a useful induction agent because it produces a quick reliable onset of general anesthesia. Several other medications target the GABAA receptor including etomidate and benzodiazepines. Benzodiazepines directly activate the GABAA receptor.

Answer 945

can lead to hypotonia in the infant Maternal administration of magnesium can have profound effects on the neonate, such as hypotonia, depressed respiratory drive, and poor feeding (secondary to poor sucking capabilities related to generalized weakness). Care is largely supportive. TrueLearn Insight : Maternal diazepam use is associated with fetal hypotonia, hypothermia, and respiratory depression.

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