GA Flashcards

Question

An Anesthetist performed airway assessment for a 22-year-old man. After examination, he concluded that the patient is in class I of upper lip bite test (ULBT). What does the class I ULBT mean? A. Intubation is extremely difficult B. Lower incisors can bite above the vermillion border of upper lip C. Lower incisors cannot reach vermilion border D. Lower incisors cannot bite upper lip

Answer 1

The extent of an individuals' ability to prognath the mandible is an important correlation of visualization of glottic structures during direct laryngoscopy. The Upper Lip Bite Test(ULBT) is used to assess the ability of patient to prognath the mandible. The Upper Lip Bite Test classification system is as follows. Class I: Lower incisors can bite above the vermilion border of the upper lip Class II: Lower incisors cannot reach vermilion border of upper lip Class III: Lower incisors cannot bite upper lip Class III is associated with a difficult intubation. Class I is associated with relatively normal intubation. However other conditions like Ludwig's angina, tumor or masses, scarring due to radiation, previous neck surgery etc can also decrease submandibular compliance and can result in difficult intubation.

Answer 2

The anesthetic implications of MG and preeclampsia are both high yield board topics. MG is an autoimmune disorder characterized by muscle weakness and fatigue resulting from destruction of acetylcholine receptors at the neuromuscular junction by autoantibodies. A history of respiratory crisis suggests high severity of the disease, which is often worsened in pregnancy. Because magnesium produces muscle weakness by inhibiting acetylcholine release, it is contraindicated in patients with MG and has been reported to cause death in cases of severe MG. Expectant management is inappropriate given the risk to the patient of progression to eclampsia, especially in the setting of avoiding magnesium prophylaxis. A neuraxial technique poses less risk to the patient than induction of general endotracheal anesthesia as it avoids the need to intubate a potentially difficult airway and the risk of stroke as a result of laryngoscopy induced hypertension. A slow titration of local anesthetic to achieve a surgical level is preferred to minimize the risk and extent of engendering further respiratory muscle weakness. The practitioner must nevertheless be prepared to escalate to general endotracheal anesthesia to support ventilation in the event of respiratory insufficiency/failure secondary to muscle weakness.

Answer 3

Endogenous catecholamines are cleared from the synaptic cleft primarily by re-uptake into neuronal and non-neuronal tissue. Remaining neurotransmitters are metabolized by degradative enzymes such as monoamine oxidase or catechol O-methyltransferase. Exogenous drugs with molecular structures similar to catecholamines, such as cocaine and tricyclic antidepressants, act as competitive inhibitors of both mechanisms of reuptake and degradation and can significantly alter the typical physiologic response to sympathomimetics. Cocaine inhibits catecholamine re-uptake. In this setting, administration of a direct-acting sympathomimetic, such as phenylephrine, produces an increased response due to the combined effect of more endogenous catecholamines remaining in the synaptic cleft in addition to the exogenous drug. Conversely, indirect sympathomimetics that depend upon the release of stored endogenous catecholamines will release vesicles with depleted stores of neurotransmitters due to impaired re-uptake and thus have a decreased response.

Answer 4

Terminology regarding memory, consciousness, and responsiveness during "general anesthesia" is often confused in the literature, by anesthesiologists, and by patients. Because various experiences and responses may have very different implications, both for postoperative patient treatment and for development of means to monitor for and prevent adverse patient experiences, it is important to be as precise as possible. General anesthesia is largely the "science of unconsciousness". Awareness itself is the subjective experience of an individual. Persons who are "unaware" do not have a subjective experience of themselves or their surroundings. . Awareness is uncoupled from recall - a person can be aware, but not remember their experience later. Responsiveness is a measure of whether a person can and does act in response to an experience. Responsiveness is dependent not only on a person's ability to perceive and experience, but their ability to act-the presence of a muscle relaxant may prevent an awake patient from responding to a verbal or surgical stimulus, even though they are aware of it and have recall of it later. Recall is the ability to remember events after they have happened and is uncoupled from awareness: a person can be aware of an event at the time of its occurrence, but unable to recall it later. Memory is a complex set of functions-there are multiple memory systems, each of which can be present without the others, and depend upon different functional areas of the brain. Episodic memory is the recollection of events with a clear spatiotemporal context (who, what, when, where). Semantic memory is the recall of facts without spatiotemporal context (i.e. the ability to remember the names of the 7 highest mountain peaks on the globe, even if the person cannot remember where or when they acquired the knowledge). Other memory various memory functions include familiarity (e.g. recognizing a face without being able to contextualize the person), short term memory, and emotional memory. In this case, the patient had a subjective experience that he can recall and describe (he remembers conversation in the operating room) and he was, therefore, aware and not unconscious for at least part of the procedure. In addition, by isolating the forearm with a tourniquet and protecting it from the effects of neuromuscular blockade, the patient was responsive. The patient may additionally have retrograde amnesia for some events: but this is difficult to judge, since we don't know the total extent of his consciousness and awareness. This patient certainly demonstrates awareness, episodic recall, and responsiveness.

Answer 5

Brown fat and skeletal muscle, which generate heat through the uncoupling of oxidative phosphorylation, is a major source of non-shivering thermogenesis at all ages, although the relative increase in heat production is higher in infants than adults. Shivering, by contrast, is not an effective method of thermogenesis until after early childhood. In adulthood, however, shivering can increase metabolic heat production by 50% to 100%. Compared to adults, children depend more on sweating for heat regulation, and are therefore more susceptible to hyperthermia after poisoning with muscarinic antagonists. It is a false perception that, surface areas being equal, heat loss from the head is greater than any other part of the body; heat loss is, in fact, simply proportional to body surface area.

Answer 6

The correct option is bilateral recurrent laryngeal nerve injury. The recurrent laryngeal nerve innervates all the muscles of the larynx except for the cricothyroid. Unilateral damage to this nerve will result in hoarseness, but bilateral damage will result in respiratory distress. Visualization of the vocal cords will show a paramedian position of the cords. Bilateral superior laryngeal nerve injury (external branch) is incorrect as that will only result in hoarseness, whereas unilateral damage will have minimal effect on the voice. Bilateral superior laryngeal nerve injury (internal branch) is incorrect as that will not result in stridor and dyspnea as it must be noted that the internal branch is sensory. Hematoma is incorrect as that results within the first few hours after surgery (generally within 6-24 hours). Also, this patient is not presenting with any signs of a hematoma.

Answer 7

Bronchospasm is a protection mechanism of the upper airway to protect the lungs from aspiration. Some triggers include intubation, history of asthma, light anesthesia or extubation. Option A is the correct answer. The tracheobronchial tree is innervated by the vagus nerve (cranial nerve X) and the vagus mediates bronchoconstriction and increases bronchial secretions. The vagus nerve is responsible for sensation to the airway below the level of the epiglottis. The branches of the vagus nerve are the superior laryngeal nerve (SLN) and the recurrent laryngeal nerve (RLN). The SLN divides into an external (motor) nerve and internal (sensory) nerve innervating the larynx between the epiglottis and the vocal cords. The RLN innervates the area between the vocal cords and the trachea. Option B is incorrect as the glossopharyngeal nerve (Cranial nerve IX) innervates the roof of the pharynx, tonsils and undersurface of the soft palate and does not participate in bronchospasm activity. Option C is incorrect because sympathetic activity T1-4 provides bronchodilation and decreases secretions. (Think fight or flight ? want bronchodilation in order to breathe better in order to fight or escape). Options D and E are incorrect because although there are alpha 1 and Beta 2 adrenergic receptors in the pulmonary vasculature, they have minimal effect on tone. Alpha 1 causes vasoconstriction and Beta 2 mediates vasodilation.

Answer 8

In the anesthetized patient, 5 seconds of sustained tetanus to 100-Hz stimulation is the most reliable indicator of adequate reversal of drug-induced neuromuscular blockade. However, in an awake patient, the application of painful train-of-four or tetanic stimulation is not greeted with a positive patient interaction. Therefore, clinical assessment of reversal of neuromuscular blockade is preferred. This includes grip strength, tongue protrusion, the ability to lift the legs off the bed, and the ability to lift the head off the bed for a full 5 seconds. Of the clinical assessment maneuvers, the 5-second sustained head lift has been considered by some to be the standard, reflecting not only generalized motor strength but, more importantly, the patient's ability to maintain and protect the airway. However, the ability to strongly oppose the incisor teeth against a tongue depressor is a more reliable indicator of pharyngeal muscle tone. This maneuver correlates with an average train-of-four ratio of 0.85 as opposed to 0.60 for the sustained head lift.

Answer 9

Perioperative mortality involves multiple factors, including but not limited to patient co-morbidities, surgical complications, and anesthesia complications. Anesthesia mortality can be measured in different ways: 1) perioperative mortality, or the number of deaths following anesthesia within a certain period of time (usually 30 days), 2) anesthesia-related mortality, in which the anesthetic is the sole or partial cause of mortality, and 3) anesthesia sole-cause mortality, in which the anesthetic itself is the cause of death. Studies of anesthesia-associated deaths can be designed to examine any of these or a combination of them, and specific statistics, therefore, can sometimes appear to be conflicting. Several things are known, however. Many studies have demonstrated that over time, anesthesia associated mortality has fallen. Between 1960 and 1984, for example, one study demonstrated that the rate of anesthesia-attributable deaths fell from 1 in 5500 to 1 in 26,000; and the rate of anesthesia-attributable death is believed to be significantly lower today than in 1984. Prospective studies of complications associated with anesthesia in France demonstrated that pulmonary complications, and postoperative respiratory depression in particular, were responsible for the largest number of post-anesthesia deaths, followed by cardiovascular events. A British study of 1 million anesthetics found that the anesthetic was the sole cause of death in 1 out of 185,000 surgeries. Both increasing age and ASA status are associated with increased mortality; one study shows that the rate of anesthesia-related deaths for ASA 3 patients is 1 to 2 per 10,000 surgical cases. One approach to this that usually sets patients' minds at ease is to say "the most dangerous part of the operation is the drive to the hospital". SOURCE: Holland R. Anaesthetic mortality in New South Wales. Br J Anaesth 1987; 59:834-41. Tiret L, Desmonts JM Hatton F, Vourc'h G. Complications associated with anaesthesia-a prospective survey in France. Can Anaesth Soc J. 1986; 33(3 Pt 1):336-44.

Answer 10

In interpreting monitoring standards, it is important first of all to appreciate the difference between "continual" (happening at frequent intervals) versus "continuous" (happening without interruption). The ASA committees are careful to use these terms explicitly in guidelines and standards statements. An arterial line, for example, provides continuous monitoring of blood pressure, whereas a blood pressure cuff provides continual monitoring. In the case of ventilator monitoring, the ASA Standard requires continual and not continuous monitoring of the adequacy of ventilation throughout a general anesthetic. If the patient is under general anesthesia via mask, the ASA Standard requires continual clinical assessment via chest excursion, observation of the reservoir breathing bag and/or auscultation of breath sounds. However, during cases utilizing a laryngeal mask airway (LMA) or tracheal intubation, the standard is raised to require in addition continual end-tidal carbon dioxide analysis form the time of LMA placement or endotracheal intubation, until extubation or removal of the LMA. It is never sufficient to have respiratory and/or ventilator and breathing circuit audible alarms turned off, and the ASA Standard explicitly requires that the be at all-time audible to the anesthesia care team.

Answer 11

Answer A is correct because IR absorption is the most commonly utilized form of CO2 monitoring. It is straightforward, reliable and relatively inexpensive compared to other choices. Mass spec is older technology used for inhaled gases. C and D are used for oxygen. E can be used for CO2 but it does not quantify it.

Answer 12

If situated correctly, the LMA distal tip rests over the upper esophageal sphincter, the wide cuff base rests against the base of the tongue and the lateral cuff walls rest over the pyriform fossae.

Answer 13

C. Moderate sedation Explanation: The ASA practice guidelines describe 4 levels of sedation: minimal sedation, moderate sedation, deep sedation, and general anesthesia. These levels of sedation are on a continuum, whereby patients can easily progress to a deeper level of anesthesia than intended. It is thus important to have continuous patient monitoring when administering sedation and be prepared if the patient enters into a deeper level of anesthesia than anticipated. The statements listed above represent a patient under moderate sedation. As defined by the ASA, minimal sedation is a patient who has normal response to verbal stimulation with unaffected airway, ventilation, and cardiovascular function. Deep sedation is defined as purposeful response following repeated or painful stimulation with possible airway intervention required, possible inadequate ventilation, but typically maintained cardiovascular function. General anesthesia is defined as a patient who is unarousable with airway intervention often required, frequently inadequate spontaneous ventilation, and possible impairment of cardiovascular function.

Answer 14

The correct option 25-30 mmHg. Instances where patients are intubated with cuffed endotracheal tubes, tracheal capillary arteriolar pressure has to be kept in mind. If the endotracheal cuff exerts a pressure greater than the capillary arteriolar pressure, tissue ischemia may result. Tracheal ring destruction and tracheomalacia will result due to persistent ischemia. Endotracheal tubes with low-pressure cuffs are indicated in patients who are to be intubated for greater than 48 hours as this reduces the chances of development of tissue ischemia.

Answer 15

``` The current ASA risk classification system is an attempt to classify the risk associated with anesthesia and surgery. It is intended to give a subjective risk based on the patient's preoperative medical history. The type of procedure is not considered in the classification scheme. ASA III patients have significant or severe systemic disease limiting normal activity, such as renal failure on dialysis or class 2 congestive heart failure. This systemic disease poses a significant impact on daily activity. ASA I is a healthy patient without biochemical or psychiatric disease. ASA II is a patient with mild systemic disease, such as mild asthma or well-controlled DM. This disease state does not pose an impact on daily activity. ASA IV describes a severe disease that is a constant threat to life or requires intensive therapy such as an intervention for an acute myocardial infarction. Such a disease state has a major impact on anesthesia and surgery. ASA V is a patient who is equally likely to die in the next 24 hours with or without surgery. ```

Answer 16

The LMA classic has an oval-shaped silicon mask with cuff that sit in laryngopharynx and help to make a seal around periglottic tissue. It contents airway tube which has a standard 15 mm diameter which is attached to anesthesia circuit or to bag valve device. The seal around the laryngeal inlet allows for delivery of oxygen and inhaled agent which permits PPV up to 20 cmH20. In this case patient is adult with age above 100 kg so size 6 SGA should be used. Once a patient starts going above 100 kg, prudence would dictate you intubate this patient since they are an aspiration risk.

Answer 17

The tracheobronchial tree is innervated by the vagus nerve (cranial nerve X) and the vagus mediates bronchoconstriction and increases bronchial secretions. The vagus nerve is responsible for sensation to the airway below the level of the epiglottis. The branches of the vagus nerve are the superior laryngeal nerve (SLN) and the recurrent laryngeal nerve (RLN). The SLN divides into an external (motor) nerve and internal (sensory) nerve innervating the larynx between the epiglottis and the vocal cords. The RLN innervates the area between the vocal cords and the trachea. although there are alpha 1 and Beta 2 adrenergic receptors in the pulmonary vasculature, they have minimal effect on tone. Alpha 1 causes vasoconstriction and Beta 2 mediates vasodilation.

Answer 18

Several physiological and pathological factors can bring about a variation in MAC of an inhalational anesthetic drug. Hyperthermia (option B) is the correct answer as an increase in the body temperature increases the requirement of an anesthetic drug. Other options are incorrect as they all act to lower MAC. Factors that increase MAC include fever, hyperthermia, stimulants acting on central nervous system (CNS), chronic alcoholism, cocaine use, and hypernatremia. Some studies also show that color of hair can influence MAC and having red hair increases MAC. Infants are also known to have higher anesthetic requirements (highest at the age of 6 months). Factors that decrease MAC include hypothermia, hyponatremia, CNS depressants, sedatives, PaCO2 > 90 mmHg, PaO2 <40 mmHg, pregnancy, acute alcohol abuse and advancing age. Studies show that there is a 6% decrease in MAC with every additional decade of life. Factors having little or no effect on MAC include duration of anesthesia, gender, height, and weight of the patient.

Answer 19

Heparin resistance, an inability to achieve therapeutic anticoagulation, has been described in as many as 22% of patients undergoing open-heart surgeries. Paradoxically, patients who receive intermittent or continuous therapy with heparin manifest a progressive reduction of antithrombin activity to values that are approximately one-third of normal. Thus, a heparin-induced decrease in the activity of antithrombin may paradoxically increase the thrombotic tendency in humans. Thrombocytopenia due to heparin administration can be divided into 2 syndromes. The most common syndrome is mild, occurring in 30% to 40% of heparin-treated patients manifesting as platelet counts of less than 100,000 cells/mm3. This mild thrombocytopenia is attributed to drug-induced platelet aggregation. It typically manifests between 3 to 15 days after initiation of therapy (median 10 days) but has been reported to begin within hours in patients previously exposed to heparin. The platelet count usually returns to baseline within 4 days after heparin is discontinued. A second, more severe and even life-threatening syndrome develops in 0.5% to 6% of patients, manifesting as severe thrombocytopenia (50,000 cells/mm3), often with associated resistance to the effects of heparin and the occurrence of thrombotic events. This severe response typically develops after 6 to 10 days of heparin therapy and is probably due to the formation of heparin-dependent antiplatelet antibodies that trigger platelet aggregation, resulting in thrombocytopenia. Heparin is obtained from animal tissues; thus, caution should be used in its administration to a patient with a preexisting history of allergies. Indeed, fever, urticaria, and even cardiopulmonary changes occasionally occur after administration of heparin. Rapid IV infusion of large doses of heparin (300 U/kg) as administered before cardiopulmonary bypass may cause modest decreases in mean arterial pressure and pulmonary artery pressure. These changes principally reflect decreases in systemic vascular resistance, perhaps due to a direct heparin-induced relaxant effect on vascular smooth muscles.

Answer 20

The correct answer is trigeminal and vagus nerves. The reflex involved in the described patient is the oculocardiac reflex. It consists of vagally-mediated bradycardia and hypotension with pressure on eye globe. The afferent limb of oculocardiac reflex is the ophthalmic branch of trigeminal nerve which transmits the impulses through the gasserian ganglion to the main trigeminal sensory nucleus. The efferent limb is the vagus nerve that inhibits the sinoatrial node at the left atrium leading to bradycardia. The oculocardiac reflex is triggered by any stimulus that causes direct pressure on the eye globe, traction to the extraocular muscles, ocular manipulation, and ocular pain. It is also activated in cases of orbital bone fracture or orbital tumors. The reflex is more pronounced in children and young healthy adults, and it tends to wane with age. Therefore, it is commonly encountered with pediatric anesthesiologists during strabismus surgery as the case mentioned in this question.

GA Flashcards

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