True Learn Questions

Question 1

A full tank of N2O contains how many liters?

Answer 1

A full tank of N2O contains 1590 L.

Question 2

A full tank of N2O contains 1590 L at what pressure?

Answer 2

A full tank of N2O contains 1590 L at a pressure of ~745 psig

Question 3

When will the pressure on a N2O cylinder begin to drop?

Answer 3

N2O is stored as a liquid and gas in a pressurized E cylinder, and the pressure within a tank of N2O will remain at ~745 psig until all liquefied gas is used up.

This occurs when the tank has ~250 L (16%) N2O remaining.

Note again that, as explained above, some textbooks state ~400 L (25%) N2O remaining before a pressure drop, but this is not backed by evidence.

There could be two answers here, know both exist.

Question 4

What is the metabolism of Lorazepam?

Answer 4

hepatic glucuronidation is significantly impaired by hepatic dysfunction.

Less susceptible to drug/drug interactions than diazepam/midazolam

Question 5

What is the metabolism of diazepam and midazolam?

Answer 5

oxidative metabolism via hepatic cytochrome oxidases

More susceptible to drug/drug interactions than diazepam/midazolam

Question 6

What is the half life of Lorazepam?

Answer 6

8-25 hours

Unpredictable, 8-25 hours is also why it’s not used for preoperataive anxiolysis

Question 7

When would you consider Lorazepam over Midazolam for anxiolysis?

Answer 7

ESRD / CKD

Because this metabolite is inactive, renal dysfunction does not impair the elimination of lorazepam or extend its duration of action.

Question 8

How does ventilation affect calcium levels?

Hyperventilation?

Hypoventilation?

Answer 8

Hyperventilation –> Alkalemia –> Less H+ –> More calcium binds albumin –> Less free serum (Hypocalcemia)

Hypoventilation –> Acidemia –> More H+ –> Less calcium binds albumin –> Less free serum (Hypocalcemia)

Question 9

How does ventilation (hyper/hypo) affect potassium levels?

Answer 9

Respiratory alkalosis (hyperventilataion) –> Hypokalemia

Respiratory acidosis (hypoventilation) –> Hyperkalemia

Why?

H⁺-K⁺ transporters pump H⁺ out of cells in the setting of alkalosis (Too few protons in the serum) to restore physiologic pH

Question 10

What is the ASRA recommendation for neuraxial management for low dose subcutaneous heparin (5000 U BID or TID) administration?

Answer 10

The new recommendations are to hold low-dose subcutaneous heparin at least 4-6 hours prior to the performance of neuraxial anesthesia,

as well as to

hold heparin 4-6 hours before the manipulation or removal of a neuraxial catheter.

Question 11

If a patient is a normal PTT but hasn’t been 4-6 hours since heparin, can you proceed with an epidural?

Answer 11

Yes

Question 12

What is the ASRA recommendation for neuraxial management for high dose subcutaneous heparin (7500 - 10000 U BID or TID) administration?

Answer 12

12 hours AND normal coagulation studies

Question 13

What is the ASRA recommendation for neuraxial management for therapeutic dose subcutaneous heparin (>20,000 units per day) administration?

Answer 13

24 hours and normal coagulataion studies

Question 14

What is the ASRA recommendation for neuraxial management for prophylactic LMWH administration?

Answer 14

12 hours

Question 15

What is the ASRA recommendation for neuraxial management for prophylactic LMWH (BID dosing) administration?

Answer 15

12 hours

Question 16

List 8 conditions approved for hyperbaric oxygen therapy.

Answer 16

Gas-bubble disease (air embolism and decompression sickness)

Carbon monoxide poisoning

Infections (clostridial myonecrosis, other soft tissue necrotizing infections, refractory chronic osteomyelitis, intracranial abscess)

Acute tissue ischemia (crush injury, compromised skin flaps, central retinal artery or vein occlusion)

Chronic ischemia (radiation necrosis, ischemic ulcers)

Acute hypoxia (exceptional blood loss anemia when transfusion is unable to be given i.e. Jehovah’s witness)

Acute thermal burn injury

Idiopathic sudden sensorineural hearing loss

Question 17

What is the only true contraindication to hyperbaric oxygen therapy?

Answer 17

Acute Untreated Pneumothorax

Patient’s can develop tension pneumothorax which can not be decompressed under hyperbaric conditions

Question 18

What is the most common underlying comorbidity in patients with HFpEF?

Answer 18

The most common underlying comorbidity in patients with HFpEF is long-standing hypertension, which leads to concentric remodeling of the left ventricle.

Question 19

What Reynolds number represents laminar flow?

What Reynolds number represents turbulent flow?

Answer 19

Laminar <2300

Variable flow zone (2300 - 4000)

Turbulent >4000

Question 20

What does Heliox (inspired helium-oxygen mixture) do to the Reynolds number?

Answer 20

Heliox, an inspired helium-oxygen mixture, may be a useful intervention for patients with postoperative stridor because of the lower density of helium compared to oxygen or ambient air. The lower density decreases the Reynolds number, which favors laminar flow rather than turbulent flow.

Question 21

This concept relates oxygen consumption to cardiac output and the oxygen content difference between arterial and venous blood

Answer 21

Fick Principle

Question 22

What 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 22

Bohr Effect

An integral part of the oxygen and hemoglobin interaction at the level of capillaries in tissues is 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.

At the level of the capillaries, PCO2 is higher than in arterial blood and the pH consequently is lower. The increase in the concentration of CO2 is due to the metabolic processes of the tissues. The higher CO2 or lower pH leads to a right shift in the oxygen dissociation curve, which leads to hemoglobin offloading the oxygen to the tissues. This increases the delivery of oxygen to acidotic and hypoxic tissues.

Question 23

What effect described hemoglobin’s ability to carry increased amounts of CO2 in the deoxygenated state as opposed to the oxygenated state

Answer 23

Haldane Effect

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.

Question 24

What valvular disease is associated with rheumatoid arthritis?

Answer 24

Mitral Regurgitation = Most common (usaully mild)

AI = Can happen too

Question 25

What are 3 reasons why rheumatoid arthritis patients can be difficult to intubate/extubate safely?

Answer 25

1. **Atlantoaxial subluxation** may make intubation more difficult and cause spinal cord trauma with neck manipulation. 2. **Temporomandibular joint synovitis** can limit mandibular motion. 3. **Cricoarytenoid arthritis** can cause hoarseness, pain on swallowing, and possible post-extubation laryngeal obstruction.

Question 26

What is the gold standard test to confirrm brain death?

Answer 26

**Cerebral angiography** gold standard for confirmatory tests, but it is invasive. The test will show absent blood flow at or beyond the carotid bifurcation or circle of Willis.

Question 27

What tests need to be seen before performing apnea test?

Answer 27

*_● Assess for absence of the following:_* **○ Pupil reaction** to light in both eyes **○ Corneal reflexes** ○ Ocular movement with head turning (**oculocephalic** reflex) when no apparent cervical spine injury exists and ocular movements after caloric testing with ice water (**oculovestibular** reflex) **○ Bulbar function** (jaw reflex) **○ Oropharyngeal reflex** (gag and cough reflex) **○ Pain reflex**

Question 28

How does *_inspiratory reserve volume_* change in pregnancy?

Answer 28

**Increase** (0-5%)

Question 29

How does *_tidal volume_* change in pregnancy?

Answer 29

Increase 40-45%

Question 30

How does *_expiratory reserve volume_* change in pregnancy?

Answer 30

**Decrease** 20-25%

Question 31

How does *_residual volume_* change in pregnancy?

Answer 31

**Decreased** 15-20%

Question 32

The functional residual capacity is made up of what two lung volumes?

Answer 32

**Residual Volume** **Expiratory Reserve Volume**

Question 33

The inspiratory capacity is made up of what lung volumes?

Answer 33

**Tidal Volume** **Inspiratory Reserve Volume**

Question 34

What is the vital capacity made up of?

Answer 34

Vital capacity Sum of **ERV** + **TV** + **IRV**

Question 35

How does vital capacity change in pregnancy?

Answer 35

Vital capacity (VC, the sum of ERV + TV + IRV) is **unchanged** in pregnancy because the *_increases in IRV and TV are largely balanced by the decrease in ERV._*

Question 36

How does the total lung capacity change in pregnancy?

Answer 36

Finally, the total lung capacity (TLC, the sum of RV + ERV + TV + IRV) is slightly **decreased** by up to 5% during normal pregnancy.

Question 37

What is the closing capacity defined as?

Answer 37

The CC is defined as the lung volume (or, more precisely, the sum of residual volume and closing volume) at which **small, non-cartilaginous airways begin to collapse, particularly the respiratory and terminal bronchioles in the dependent areas of the lung.**

Question 38

Does closing capacity change in pregnancy?

Answer 38

No

Question 39

What are the stages of labor?

Answer 39

Labor is divided into 3 stages. The **first stage** begins with the *_maternal perception of regular, painful uterine contractions and ends with complete dilation of the cervix._* The **second stage** begins with *_complete dilation of the cervix and ends with the birth of the baby._* The **third stage** begins with the *_birth of the baby and ends with the delivery of the placenta_*

Question 40

*_What spinal segments_* spinal segment coverage is required to relieve the pain of contractions and cervical dilation?

Answer 40

***_T10 to L1_*** spinal segment coverage is required to relieve the pain of contractions and cervical dilation

Question 41

*_What spinal segments_* spinal segment coverage is required to relieve the pain of vaginal and perineal distention?

Answer 41

***_S2-S4_*** spinal segment coverage is required to relieve the pain of vaginal and perineal distention.

Question 42

What isolated nerve block is helpful for the second stage of labor?

Answer 42

**Pudendal nerve block** helps relieve pain during the second stage of labor. The pudendal nerve includes somatic nerve fibers from **S2-S4.**

Question 43

Why is Sodium Bicarbonatae added to local anesthetics for blocks?

Answer 43

**Sodium bicarbonate** is chiefly added to increase the rate of onset of anesthesia by increasing local pH, thus facilitating entry of uncharged local anesthetic into neurons.

Question 44

Why is Epinephrine added to local anesthetics for blocks/epidurals/spinals?

Answer 44

1. May reduce systemic absorption (and toxicity) of the local anesthetic by **decreasing local blood flow** through vasoconstriction. 2. Epinephrine-induced vasospasm also **prolongs the duration of action** of the local anesthetic by maintaining its effects at the injection site. The addition of epinephrine allows for intravascular injection to be detected early through an increase in heart rate or blood pressure in response to incremental dosing. 3. Finally, the **quality and density of the block may be augmented by local vasoconstriction** as well as the intrinsic analgesic effects of epinephrine, which hinge on its alpha2-adrenergic agonist activity

Question 45

Does epinephrine affect the onset of the regional/neuraxial block?

Answer 45

No

Question 46

What is the mcg/mL concentrations of Epinephrine for: 1: 1,000 1: 10,000 1: 100,000 1: 200,000

Answer 46

1: 1,000 = 1000 mcg/mL (1 mg / mL) 1: 10,000 = 100 mcg/mL 1: 100,000 = 10 mcg/mL 1: 200,000 = 5 mcg/mL

Question 47

The transtracheal block, anesthetizes whta nerve?

Answer 47

The translaryngeal block can be used to safely anesthetize the tracheal mucosa, which draws sensory innervation from the **recurrent laryngeal nerve**

Question 48

*_What nerve block_* is used to anesthetize the hypopharynx and larynx above the vocal cords?

Answer 48

***_Superior laryngeal nerve block_*** is used to anesthetize the hypopharynx and larynx above the vocal cords

Question 49

**What nerve block** can be used to anesthetize much of the oropharynx and tongue base?

Answer 49

**Glossopharyngeal nerve block** can be used to anesthetize much of the oropharynx and tongue base

Question 50

The external iliac arteries become the *_what arteries_* after the groin crease?

Answer 50

The external iliac arteries become the **common femoral artery** after the groin crease.

Question 51

The common femoral artery branches off into *_what two arteries?_*

Answer 51

The common femoral artery branches off into: ## Footnote **1. The deep femoral artery (profunda femoris)** **2. The superficial femoral artery**

Question 52

The superficial femoral artery continues down the leg and becomes *_what artery_* at the knee crease?

Answer 52

**Popliteal Artery**

Question 53

The popliteal artery branches off into what two arteries?

Answer 53

The popliteal artery branches off into the **anterior tibial artery** and the **tibiofibular (tibioperoneal) trunk**

Question 54

The tibioperoneal (TP) trunk bifurcates into what two arteries?

Answer 54

The tibioperoneal (TP) trunk bifurcates into the **posterior tibial artery** and the **fibular (peroneal) artery.**

Question 55

Phosgene creates what **end organ damage**? **Antidote** & **Treatment**?

Answer 55

Phosgene is a chemical warfare agent that can lead to **significant pulmonary damage.** There is **no specific antidote** Treatment is generally centered around providing supportive care and minimizing the effects of the inflammatory mediator cascade.

Question 56

What is the Liver's blood supply?

Answer 56

The liver has a unique **dual blood supply** Receiving blood from both the **hepatic artery**, which arises from the celiac trunk, as well as the **portal vein**, which is a confluence of the venous drainage from the splanchnic circulation

Question 57

**Compare hepatic artery vs. portal vein** 1. % of blood Flow 2. % of Oxygen Supply

Answer 57

The hepatic artery provides **25% of the blood flow** Portal Vein provides **75% of blood flow (Think Portal = Plump and lots of blood)** *_Oxygen supply 50% and 50% for each_*

Question 58

The primary means of physiologic hepatic blood flow?

Answer 58

The primary means of intrinsic autoregulation of hepatic blood flow is the hepatic arterial buffer response that causes **adenosine-mediated vasodilation** of the hepatic artery in response to **decreased blood flow in the portal vein.** *_Think about this as a compensatory way to increase Liver blood flow_*

Question 59

**When does the HABR effect reach maximum capacity?** HABR = Hepatic Arterial Buffer Response

Answer 59

The HABR reaches its maximal effect when the **hepatic arterial flow is doubled** and will not increase blood flow in the hepatic artery past this point. Even in this case, the oxygen supply to the liver is preserved because the hepatic arterial blood carries more oxygen compared with the partially deoxygenated blood in the portal vein. Certain endotoxins can obliterate this response and leave the liver vulnerable to ischemic or hypoxic injury.

Question 60

**How does Volatile Anesthetics affect HABR?** HABR = Hepatic Artery Buffer Response

Answer 60

Most volatile anesthetics will tend to **attenuate this response***_, resulting in a muted vasodilation of the hepatic artery_* in direct response to decreased portal venous pressures

Question 61

What can happen to uterine blood flow when a mother **hypoventilates**?

Answer 61

Note that **maternal hypocapnea** can cause *_fetal hypoxia and acidosis secondary to vasoconstriction, decreased venous return_* (hypocapnea is usually the result of hyperventilation and increased thoracic pressure), and left shift of the maternal oxygen dissociation curve (CO2 leads to unloading of O2, hypocapnea leads to retention of O2)

Question 62

What are the only procedures that warrant infective endocarditits antibiotic prophylaxis?

Answer 62

**Dental or oral surgery** procedures that "involve the manipulation of gingival tissue...periapical region of teeth, or perforation of the oral mucosa"

Question 63

What are the 5 high risk cardiac conditions that warrant infective endocarditis prophylaxis?

Answer 63

1. **Prosthetic cardiac valves**, including transcatheter-implanted prosthetic valves 2. Patients with **implanted prosthetic material,** such as annuloplasty rings and artificial chordae tendineae 3. Patients with a **history of infectious endocarditis** 4. Patients with a history of **unrepaired cyanotic congenital heart disease**, including patients with a **repair, but with a residual shunt or valvular regurgitation** near an implanted patch or device Patients with a **history of cardiac transplantation who have a regurgitant valvular lesion** due to a structurally abnormal valve

Question 64

What is the conversion rate of mmHg --\> cm H20?

Answer 64

Conversion rate is 1 mmHg = 1.36 cmH2O.

Question 65

Are the rings of the trachea anterior or posterior?

Answer 65

Rings = Anterior Trachealis muscle = Posterior (Longitudinal fibers)

Question 66

What is the Bronchus Intermedius?

Answer 66

The **bronchus intermedius** is the *_distal portion of the right main bronchus_* after the takeoff of the right upper lobe and before the takeoffs of the right lower and middle lobes.

Question 67

How does ***_pH & PaCO2 tension_*** affect Hemoglobin dissociation shift curves?

Answer 67

Acidosis and Increase in PaCO2 shift Right

Question 68

How does ***_temperature_*** affect Hemoglobin dissociation shift curves?

Answer 68

Increase temperature = Right shift Decrease in temperature = Left shift

Question 69

How does **stored PRBC** affect Hemoglobin dissociation shift curves?

Answer 69

Left Shift

Question 70

How does hypophosphatemia affect Hemoglobin dissociation shift curves?

Answer 70

Left Shift (Decreased DPG)

Question 71

What are 6 causes of increase in 2,3 DPG that would cause a Right Shift on Hgb dissociation curve?

Answer 71

1. Hyper-phosphatemia 2. Thyroxine (Hyperthyroidism) 3. Anemia 4. Liver Cirrhosis 5. Sleep Apnea (OSA) 6. Herat Failure 7. High Altitude Hypxia

Question 72

The treatment of choice for type 1 vWD is desmopressin when factor VIII levels are *_what percent_*?

Answer 72

\<50%

Question 73

What is the most common congenital bleeding disorder?

Answer 73

**von Willebrand disease** is the most common congenital bleeding disorder, with a prevalence of up to 1%,

Question 74

What are the Subtypes of Von Willebrand Disease?

Answer 74

1 = Partial Quantitative Deficiency 2 = Qualitative deficiency (Types A, B, M, N) 3 = Complete Deficiency

Question 75

For Type I vWD disease, what is the cutoff for treating with desmopressin?

Answer 75

Typically for type 1, women do not require treatment during pregnancy when factor VIII levels are \>50%. ***_If levels are \<50%_***, then treatment should be initiated

Question 76

If you have a pregnant woman with vWD Type I and you give desmopressin, what can happen? (List 2 things)

Answer 76

1. Tachyphylaxis 2. Initiation of Uterine Contractions

Question 77

If you have a patient with vWD (Type II and Type III) what should be administered?

Answer 77

Humate-P (Factor 8) Alphanate (vWF)

Question 78

Can you use FFP to treat for vWD?

Answer 78

Fresh frozen plasma does contain functional vWF and factor VIII; however, *_it is not the preferred method of providing these because of exposure to allogeneic blood products_* and the other components of plasma that are not required. If replacement is indicated, factor VII and vWF concentrates are preferred.