General Anesthesia Practice Questions

Q: A patient with myasthenia gravis requires surgery. Which muscle relaxant requires the most caution and dose adjustment?

Atracurium. ***Atracurium*** - While **atracurium** can be used in patients with myasthenia gravis, its prolonged duration of action and **non-depolarizing** mechanism necessitate careful **dose reduction** and close monitoring. - Patients with myasthenia gravis have fewer **acetylcholine receptors** at the neuromuscular junction, making them highly sensitive to non-depolarizing muscle relaxants. *Rocuronium* - **Rocuronium** is a **non-depolarizing** muscle relaxant with a relatively short onset but a longer duration of action, typically requiring significant dose reduction in myasthenia gravis patients. - Its use necessitates careful titration due to increased sensitivity and potential for **prolonged paralysis**. *Vecuronium* - **Vecuronium** is an intermediate-acting **non-depolarizing** muscle relaxant that requires substantial dose reduction in patients with myasthenia gravis. - Its effects can be prolonged, leading to an increased risk of **residual neuromuscular blockade**. *Succinylcholine (a depolarizing muscle relaxant)* - Patients with myasthenia gravis are often **resistant** to succinylcholine due to the reduced number of **acetylcholine receptors** at the neuromuscular junction. - While a higher dose might be needed, it still carries risks due to unpredictable responses and potential for **prolonged phase II block** in susceptible individuals.

Q: Which anesthetic agent is known to lead to bradycardia?

Propofol. ***Propofol*** - Propofol can cause **bradycardia** and **hypotension** due to its effects on the autonomic nervous system, leading to a decrease in sympathetic tone and an increase in vagal activity. - This effect is often more pronounced with **rapid bolus administration** or in patients with preexisting cardiovascular conditions. *Sevoflurane* - Sevoflurane is an inhaled anesthetic that typically causes **little change in heart rate** or can lead to a slight increase, rather than bradycardia. - It is known for its **hemodynamic stability** and is often preferred for induction, especially in pediatric patients. *Isoflurane* - Isoflurane, another inhaled anesthetic, tends to cause **tachycardia** due to its ability to increase heart rate, especially at higher concentrations. - This effect is mediated by sympathetic activation and a decrease in systemic vascular resistance. *Desflurane* - Desflurane is an inhaled anesthetic that can cause significant and rapid increases in **heart rate** and blood pressure, particularly with rapid increases in concentration. - This **sympathetic stimulation** often necessitates careful titration to avoid adverse cardiovascular effects.

Q: In the human body, trichloroethylene (trilene) is primarily metabolized by which process?

Enzymatic Oxidation. ***Enzymatic Oxidation*** - Trichloroethylene (TCE) is primarily metabolized in the human body through **enzymatic oxidation** by hepatic **cytochrome P450 enzymes**, particularly **CYP2E1** - The oxidative pathway converts TCE to reactive intermediates including **chloral hydrate**, which is further metabolized to **trichloroethanol** and **trichloroacetic acid** - A minor pathway involves **glutathione conjugation**, forming reactive metabolites that contribute to nephrotoxicity - This enzymatic oxidation is the principal metabolic pathway in humans and is responsible for both detoxification and generation of toxic metabolites *Thermal Degradation* - Thermal degradation refers to breakdown of compounds at **high temperatures**, which is an industrial or environmental process - This is not a physiological metabolic pathway in the human body, where temperatures remain constant at 37°C - This process is relevant for TCE disposal or industrial accidents, not human metabolism *Photodegradation* - Photodegradation involves breakdown by **light energy (UV radiation)** and occurs in environmental settings like the atmosphere - The human body does not use photodegradation as a metabolic pathway - Internal organs where TCE metabolism occurs (liver, kidneys) are not exposed to UV light *Chemical Hydrolysis* - Chemical hydrolysis is a non-enzymatic reaction with water that can occur with some compounds - While TCE can undergo limited hydrolysis to form **dichloroacetic acid**, this is a **minor pathway** compared to enzymatic oxidation - The predominant metabolic route for TCE in humans is enzymatic, not simple chemical hydrolysis

Q: What is the anesthetic agent of choice for patients with asthma?

Ketamine. ***Ketamine*** - **Ketamine** is preferred due to its **bronchodilatory** properties, making it beneficial for patients with reactive airway disease like asthma. - It also maintains **cardiovascular stability** and preserves respiratory drive, reducing the risk of bronchospasm. *Thiopentone* - **Thiopentone** can cause **histamine release**, which may lead to **bronchoconstriction** and exacerbate asthma. - It is known for its **cardiovascular depressant** effects, which can be detrimental in patients with compromised respiratory function. *Methexitone* - **Methohexital**, a barbiturate similar to thiopentone, can also induce **histamine release** and carries a risk of **bronchospasm**. - Its use is generally avoided in asthmatic patients due to potential airway reactivity. *Propofol* - While generally safe and has some **bronchodilatory** effects, **Propofol** can cause significant **respiratory depression** and **hypotension**, which might not be ideal for all asthmatic patients, especially during induction. - However, in specific situations, it can be used cautiously, but **ketamine** remains the agent of choice for its more pronounced bronchodilatory effects without significant cardiorespiratory depression.

Q: Propofol vial, once opened, should be used within?

6 hours. ***6 hours*** - Propofol is formulated as a **lipid emulsion**, which makes it susceptible to **microbial growth** once the vial is opened or its sterility is compromised. - The 6-hour limit is established to minimize the risk of bacterial contamination and subsequent **sepsis** in patients due to its characteristic as a lipid emulsion. *2 hours* - While a shorter duration would further reduce contamination risk, the **pharmacological stability** and risk profile of propofol generally allow for a longer period of safe use. - This time frame is typically considered too restrictive given common clinical administration protocols and the inherent properties of the drug. *4 hours* - This duration is a common misconception or a guideline used in some specific protocols, but the generally accepted and most conservative guideline for propofol use after opening is 6 hours. - Adhering to a 4-hour rule may lead to unnecessary drug wastage without a significant increase in patient safety over the 6-hour standard. *8 hours* - An 8-hour period significantly **increases the risk of bacterial contamination** and subsequent infection, especially with a lipid emulsion like propofol which acts as a rich culture medium. - Exceeding the 6-hour guideline is not recommended as it poses a substantial patient safety risk and is against established best practices for medication handling.

Q: Etomidate is not used for long term infusion because?

Results in adrenal suppression. ***Results in adrenal suppression*** - **Etomidate inhibits 11-beta-hydroxylase**, a key enzyme in the adrenal gland responsible for cortisol and aldosterone synthesis. - Prolonged infusion can lead to significant and sustained **adrenal insufficiency**, which can be detrimental, especially in critically ill patients. *May cause vasospasm* - **Vasospasm** is not a known or primary side effect of etomidate, which is generally considered hemodynamically stable. - Other agents, such as some vasopressors or illicit drugs, are more commonly associated with vasospasm. *Results in cardiac arrhythmias* - Etomidate is noted for its **cardiovascular stability** and is often preferred in patients with compromised cardiac function. - It does not typically cause cardiac arrhythmias; rather, it often maintains stable heart rate and blood pressure. *May cause increase in ICP* - On the contrary, etomidate is known to **decrease cerebral blood flow (CBF)** and **intracranial pressure (ICP)** by causing cerebral vasoconstriction. - This property makes it a favorable choice for induction in patients with neurological concerns and elevated ICP.

Q: Which of the following anesthetic agents is the most lipid soluble?

Methoxyflurane. **Methoxyflurane** - Methoxyflurane has a very **high lipid solubility**, reflected in its **blood:gas partition coefficient of 12.1**, which is the highest among common inhaled anesthetics. - This high lipid solubility means it readily dissolves in lipids, allowing for an increased amount of the drug to be taken up by tissues, leading to **slow induction and emergence**. *Nitrous oxide* - Nitrous oxide has very **low lipid solubility**, with a **blood:gas partition coefficient of 0.47**. - This makes it a **fast-acting** agent with rapid induction and emergence due to its minimal dissolution in blood and tissues. *Isoflurane* - Isoflurane has an intermediate lipid solubility among volatile anesthetics, with a **blood:gas partition coefficient of 1.4**. - It is commonly used due to its good balance between **potency** and a reasonably **fast onset/offset**. *Halothane* - Halothane has a relatively high lipid solubility with a **blood:gas partition coefficient of 2.3**. - While higher than isoflurane and nitrous oxide, it is still significantly lower than that of **methoxyflurane**, indicating faster kinetics.

Q: A patient with normal succinylcholine metabolism will have Dibucaine number between?

70-80. ***70-80*** - A Dibucaine number of **70-80** indicates normal function of **pseudocholinesterase (butyrylcholinesterase)**, the enzyme responsible for metabolizing succinylcholine. - This range signifies that dibucaine inhibits approximately 70-80% of the enzyme's activity, consistent with a **typical enzyme variant**. *20-30* - A Dibucaine number of **20-30** suggests a **homozygous atypical pseudocholinesterase**, leading to severely impaired succinylcholine metabolism. - Patients with this range would experience prolonged paralysis and respiratory depression after succinylcholine administration. *40-45* - A Dibucaine number of **40-45** indicates a **heterozygous atypical pseudocholinesterase**, causing moderately prolonged succinylcholine metabolism. - These individuals would have a somewhat extended duration of succinylcholine action compared to those with normal enzyme function. *50-60* - A Dibucaine number of **50-60** typically suggests a less common **heterozygous atypical variant** with slightly better function than the "atypical" variant, but still not within the normal range. - While better than 20-30 or 40-45, it still implies a potential for prolonged succinylcholine effect.

Q: Which of the following inhalational agents sensitizes myocardium to catecholamines

Halothane. ***Halothane*** - **Halothane** is known to significantly **sensitize the myocardium to circulating catecholamines**, increasing the risk of arrhythmias, particularly ventricular extrasystoles. - This effect is due to its interaction with calcium channels and other cellular mechanisms that alter cardiac excitability. *Desflurane* - While Desflurane can cause a **transient increase in heart rate and blood pressure** upon rapid increase in concentration, it does not sensitize the myocardium to catecholamines to the same extent as halothane. - Its cardiovascular effects are usually mediated by sympathetic nervous system activation rather than enhanced myocardial sensitivity. *Nitrous Oxide* - **Nitrous oxide** has minimal direct effects on the myocardium and does not sensitize it to catecholamines. - It tends to have a mild sympathomimetic effect, but its impact on cardiac excitability is generally considered benign. *Enflurane* - **Enflurane** has a moderate effect on the cardiovascular system, causing dose-dependent myocardial depression. - However, it does not significantly sensitize the myocardium to catecholamines in the same problematic way that halothane does.

Question 1

A 50-year-old male with severe obesity is scheduled for bariatric surgery. Which anesthetic consideration is crucial for this patient?

Accepted Answer

Caution with nitrous oxide use

Answer

Use of short-acting agents

Answer

Preoperative fasting of 12 hours

Answer

Standard doses of muscle relaxants based on actual body weight

Question 2

A patient with myasthenia gravis requires surgery. Which muscle relaxant requires the most caution and dose adjustment?

Accepted Answer

Atracurium

Answer

Rocuronium

Answer

Vecuronium

Answer

Succinylcholine (a depolarizing muscle relaxant)

Question 3

Which anesthetic agent is known to lead to bradycardia?

Accepted Answer

Propofol

Answer

Desflurane

Answer

Sevoflurane

Answer

Isoflurane

Question 4

In the human body, trichloroethylene (trilene) is primarily metabolized by which process?

Accepted Answer

Enzymatic Oxidation

Answer

Thermal Degradation

Answer

Photodegradation

Answer

Chemical Hydrolysis

Question 5

What is the anesthetic agent of choice for patients with asthma?

Accepted Answer

Ketamine

Answer

Thiopentone

Answer

Methexitone

Answer

Propofol

Question 6

Propofol vial, once opened, should be used within?

Accepted Answer

6 hours

Answer

2 hours

Answer

4 hours

Answer

8 hours

Question 7

Etomidate is not used for long term infusion because?

Accepted Answer

Results in adrenal suppression

Answer

May cause vasospasm

Answer

Results in cardiac arrhythmias

Answer

May cause increase in ICP

Question 8

Which of the following anesthetic agents is the most lipid soluble?

Accepted Answer

Methoxyflurane

Answer

Nitrous oxide

Answer

Isoflurane

Answer

Halothane

Question 9

A patient with normal succinylcholine metabolism will have Dibucaine number between?

Accepted Answer

70-80

Answer

20-30

Answer

40-45

Answer

50-60

Question 10

Which of the following inhalational agents sensitizes myocardium to catecholamines

Accepted Answer

Halothane

Answer

Desflurane

Answer

Nitrous Oxide

Answer

Enflurane

General Anesthesia — MCQs

General Anesthesia — MCQs

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