General Anesthesia Practice Questions

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.

Q: Which is a safe muscle relaxant in renal failure?

Cisatracurium. ***Cisatracurium*** - It is eliminated by **Hofmann elimination**, a non-enzymatic chemical degradation process that does not rely on renal or hepatic function. - Its metabolism generates **laudanosine**, which is minimally active and primarily excreted by the kidneys, but its impact is negligible in typical dosing. *Rocuronium* - Primarily eliminated by the **liver**, with a small percentage excreted renally. - In renal failure, its **duration of action can be prolonged** due to decreased excretion and potential accumulation of metabolites. *Vecuronium* - Undergoes **hepatic metabolism** to active metabolites, which are then excreted renally. - In patients with renal dysfunction, the **active metabolites can accumulate**, significantly prolonging its neuromuscular blockade. *Succinylcholine* - Metabolized by **plasma pseudocholinesterase**, an enzyme not significantly affected by renal failure. - However, in renal failure patients with **hyperkalemia**, succinylcholine use is contraindicated due to its potential to further increase serum potassium, leading to dangerous arrhythmias.

Q: Which muscle relaxant has the longest duration of action?

Doxacurium. ***Doxacurium*** - **Doxacurium** is a long-acting, non-depolarizing neuromuscular blocker, meaning it typically has the longest duration of action among the options provided. - Its prolonged effect is due to its **slow metabolism** and **renal excretion**, leading to an estimated duration of action of 90-120 minutes. *Rocuronium* - **Rocuronium** is an intermediate-acting non-depolarizing neuromuscular blocker, with a typical duration of action of 30-40 minutes after an intubating dose. - It has a rapid onset, making it suitable for **rapid sequence intubation**, but its duration is significantly shorter than doxacurium. *Vecuronium* - **Vecuronium** is an intermediate-acting non-depolarizing neuromuscular blocker, similar to rocuronium, with a duration of action around 25-40 minutes. - It is often favored in patients with **renal insufficiency** as it undergoes significant hepatic metabolism and biliary excretion, but its duration is not as long as doxacurium. *Atracurium* - **Atracurium** is an intermediate-acting non-depolarizing neuromuscular blocker, known for its unique metabolism via **Hofmann elimination** and ester hydrolysis, independent of renal or hepatic function. - Its duration of action is typically 20-35 minutes, making it shorter-acting than doxacurium.

Q: Which anesthetic gas is known for causing maximum respiratory irritation?

Desflurane. ***Desflurane*** - **Desflurane** is known for its **pungent odor** and tendency to cause significant **respiratory irritation** (e.g., coughing, breath-holding, laryngospasm) upon induction, especially at higher concentrations. - This irritation is exacerbated by its **low blood-gas solubility**, leading to rapid increases in alveolar concentration and rapid achievement of brain partial pressure. *Halothane* - **Halothane** is a potent anesthetic but is generally associated with less respiratory irritation compared to desflurane due to its **less pungent odor**. - Its main concerns include **hepatotoxicity** (halothane hepatitis) and cardiac arrhythmias, not primary respiratory irritation. *Enflurane* - **Enflurane** can cause some respiratory irritation, but it is generally less irritating than desflurane. - It is also associated with a risk of **seizures** at higher concentrations, making it less commonly used. *Sevoflurane* - **Sevoflurane** is known for its **non-pungent odor** and minimal respiratory-irritant properties, making it an excellent choice for **inhalational induction**, especially in pediatric patients. - While it can generate compound A (a nephrotoxic substance) with CO2 absorbents, it is very well tolerated by the respiratory system.

Q: IV administration of which anesthetic drug is most painful among the following?

Propofol. ***Propofol*** - **Propofol** is notoriously known for causing **significant pain on injection** due to its formulation with **soybean oil emulsion** and its direct irritation of venous free nerve endings. - This pain is often described as a **burning sensation** and can be severe enough to require pre-treatment with lidocaine or administering it in a larger vein. *Methohexital* - While **methohexital** can cause localized pain and sometimes **thrombophlebitis** during intravenous administration, it is generally considered less painful than propofol. - It is a **barbiturate** and its discomfort is typically related to its alkaline pH and potential for venous irritation. *Ketamine* - **Ketamine** typically causes **minimal pain on injection** when administered intravenously. - Its mechanism of action as an **NMDA receptor antagonist** does not generally involve direct irritation of venous endothelium in the same way as propofol. *Etomidate* - **Etomidate**, like methohexital, can cause some **pain and irritation on injection**, and poses a risk of **thrombophlebitis**. - However, the severity of pain is generally **less pronounced** compared to the distinct and often intense burning sensation associated with propofol.

Q: All of the following statements about neuromuscular blockage produced by succinylcholine are true, except for:

Fade on tetanic stimulation. ***Fade on tetanic stimulation*** - Succinylcholine is a **depolarizing neuromuscular blocker** that initially causes fasciculations and then sustained depolarization. - In a typical depolarizing block (Phase I), there is **no fade** with tetanic or train-of-four (TOF) stimulation due to continuous activation of nicotinic receptors. *Sustained contraction during tetany* - **Sustained contraction during tetany** is characteristic of a depolarizing block (Phase I) where the muscle remains depolarized and unresponsive. - The muscle fibers are continuously stimulated, leading to a prolonged contractile state or paralysis without fade. *Train of four ratio < 0.4* - A **Train-of-Four (TOF) ratio < 0.4** indicates a **fade** in muscle response, which is a hallmark of a **non-depolarizing block (Phase II block)**. - In a typical depolarizing block (Phase I), the TOF ratio is close to 1 because there is no fade. *No fade on Train of four stimulation* - **No fade on Train-of-Four (TOF) stimulation** is a characteristic of a **depolarizing neuromuscular block (Phase I block)**. - This occurs because succinylcholine continuously activates the acetylcholine receptors, maintaining a persistent depolarization throughout the TOF stimuli.

Q: Which one of the following agents sensitizes the myocardium to catecholamines?

Halothane. ***Halothane*** - **Halothane** sensitizes the myocardium to the arrhythmogenic effects of **catecholamines**, leading to an increased risk of ventricular arrhythmias, especially in the presence of exogenous adrenaline. - This sensitization occurs due to its effect on myocardial **calcium ion** regulation and increased automaticity in cardiac pacemaker cells. *Isoflurane* - **Isoflurane** causes minimal sensitization of the myocardium to catecholamines compared to halothane. - It maintains **cardiac output** with a dose-dependent decrease in systemic vascular resistance. *Ether* - **Diethylether** historically caused sympathetic stimulation, which could mask some depressant effects but did not primarily sensitize the myocardium to arrhythmias from exogenous catecholamines. - Its use has largely been replaced due to its flammability and slower induction/recovery. *Propofol* - **Propofol** generally causes myocardial depression and vasodilation, but it does **not sensitize** the myocardium to catecholamines in a clinically significant way that increases arrhythmogenic risk. - It often leads to a decrease in **blood pressure** and heart rate.

Q: At the end of anaesthesia after discontinuation of nitrous oxide and removal of endotracheal tube, 100% oxygen is administered to the patient to prevent:

Diffusion Hypoxia. ***Diffusion Hypoxia*** - Post-anaesthesia administration of 100% oxygen prevents **diffusion hypoxia**, a phenomenon where **nitrous oxide** rapidly diffuses out of the blood into the alveoli, diluting alveolar oxygen and carbon dioxide. - This rapid outflow of nitrous oxide can lead to a significant drop in **partial pressure of oxygen** in the alveoli, causing hypoxemia if not counteracted with high inspired oxygen. *Second gas effect* - The **second gas effect** refers to the phenomenon where the rapid uptake of a highly soluble anesthetic (like nitrous oxide) accelerates the uptake of a co-administered less soluble anesthetic. - This is an effect related to the **induction phase** of anesthesia, not emergence, and is distinct from the issues arising from nitrous oxide washout. *Bronchospasm* - **Bronchospasm** is an acute constriction of the bronchioles, often triggered by irritants, allergens, or certain medications. - While it can occur during emergence from anesthesia, it is not directly prevented by administering 100% oxygen and is typically managed with bronchodilators. *Hyperoxia* - **Hyperoxia** is a condition of excess oxygen in the body, which can be detrimental, but it is not the primary concern immediately following the discontinuation of nitrous oxide. - Administering 100% oxygen in this context is a **controlled, short-term measure** to prevent a more immediate and severe issue (hypoxia) rather than causing chronic hyperoxia.

Q: What is the ionized calcium (IC) content of Ringer's lactate in mmol/L, and why is it clinically significant?

4 mmol/L. ***4 mmol/L*** - Ringer's lactate contains **calcium chloride**, contributing to its ionized calcium content of **4 mmol/L**. - This calcium is a critical component for **blood clotting** and **cardiac function**, making it clinically significant, particularly in large volume resuscitation. *130 mmol/L* - This value is close to the **sodium content** of Ringer's lactate, not its ionized calcium. - Sodium is the primary determinant of **fluid balance** and **osmolarity**, distinct from calcium's roles. *109 mmol/L* - This value approximates the **chloride content** of Ringer's lactate, which is important for acid-base balance but not its ionized calcium. - Chloride's primary role is in maintaining **electrical neutrality** and fluid distribution. *0 mmol/L* - Ringer's lactate is a **balanced electrolyte solution** and definitely contains calcium. - A value of 0 would indicate the absence of calcium, which would contradict its formulation and clinical utility, especially in scenarios requiring **electrolyte repletion**.

Q: Which inhalational agent has the least MAC?

Halothane. ***Halothane*** - **Halothane** has a **MAC** of approximately **0.75%**, which is among the lowest for commonly used volatile anesthetics. - A lower **MAC** indicates a higher potency, meaning a lower concentration is needed to achieve anesthetic effect. *Xenon* - **Xenon** has a **MAC** of approximately **71%**, making it one of the least potent inhalational agents. - It is an inert gas with unique anesthetic properties, but its high **MAC** is a key characteristic. *Sevoflurane* - **Sevoflurane** has a **MAC** of approximately **2.0%**, which is higher than halothane. - It is known for its rapid onset and offset due to its low blood solubility. *Isoflurane* - **Isoflurane** has a **MAC** of approximately **1.15%**, which is higher than halothane. - It is often favored for its cardiovascular stability and relatively low metabolism.

Question 1

Which of the following inhalational agents sensitizes myocardium to catecholamines

Accepted Answer

Halothane

Answer

Desflurane

Answer

Nitrous Oxide

Answer

Enflurane

Question 2

Which is a safe muscle relaxant in renal failure?

Accepted Answer

Cisatracurium

Answer

Vecuronium

Answer

Succinylcholine

Answer

Rocuronium

Question 3

Which muscle relaxant has the longest duration of action?

Accepted Answer

Doxacurium

Answer

Rocuronium

Answer

Vecuronium

Answer

Atracurium

Question 4

Which anesthetic gas is known for causing maximum respiratory irritation?

Accepted Answer

Desflurane

Answer

Halothane

Answer

Enflurane

Answer

Sevoflurane

Question 5

IV administration of which anesthetic drug is most painful among the following?

Accepted Answer

Propofol

Answer

Ketamine

Answer

Etomidate

Answer

Methohexital

Question 6

All of the following statements about neuromuscular blockage produced by succinylcholine are true, except for:

Accepted Answer

Fade on tetanic stimulation

Answer

Sustained contraction during tetany

Answer

Train of four ratio < 0.4

Answer

No fade on Train of four stimulation

Question 7

Which one of the following agents sensitizes the myocardium to catecholamines?

Accepted Answer

Halothane

Answer

Isoflurane

Answer

Ether

Answer

Propofol

Question 8

At the end of anaesthesia after discontinuation of nitrous oxide and removal of endotracheal tube, 100% oxygen is administered to the patient to prevent:

Accepted Answer

Diffusion Hypoxia

Answer

Second gas effect

Answer

Bronchospasm

Answer

Hyperoxia

Question 9

What is the ionized calcium (IC) content of Ringer's lactate in mmol/L, and why is it clinically significant?

Accepted Answer

4 mmol/L

Answer

0 mmol/L

Answer

130 mmol/L

Answer

109 mmol/L

Question 10

Which inhalational agent has the least MAC?

Accepted Answer

Halothane

Answer

Xenon

Answer

Sevoflurane

Answer

Isoflurane

General Anesthesia — MCQs

General Anesthesia — MCQs

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