General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 491: Muscle relaxant ideal for rapid intubation and short procedures is:

A. Rocuronium (Correct Answer)
B. Atracurium
C. Suxamethonium
D. Vecuronium

Explanation: ***Rocuronium*** - **Rocuronium** has a rapid onset of action (60-90 seconds) and an intermediate duration of action (30-60 minutes), making it suitable for rapid sequence intubation. - Its effects can be rapidly reversed by **sugammadex**, allowing for controlled and quick recovery when needed for short procedures. *Atracurium* - **Atracurium** has an intermediate onset (2-3 minutes) and duration of action (20-35 minutes), which is slower than ideal for rapid intubation. - It undergoes **Hofmann elimination** and ester hydrolysis, making it suitable for patients with renal or hepatic dysfunction, but not primarily for rapid onset. *Suxamethonium* - **Suxamethonium** (succinylcholine) has the most rapid onset of action (30-60 seconds) among muscle relaxants, historically making it the drug of choice for rapid sequence intubation. - However, its side effects, such as **malignant hyperthermia**, hyperkalemia, and prolonged paralysis in patients with atypical pseudocholinesterase, limit its use where alternative agents like rocuronium are available and suitable. *Vecuronium* - **Vecuronium** has an intermediate onset (2-3 minutes) and duration of action (25-40 minutes), making it too slow for rapid sequence intubation. - It is often chosen for its minimal cardiovascular effects and moderate duration, making it suitable for procedures where a longer duration of paralysis is acceptable, but not for rapid intubation.

Question 492: A patient with mild to moderate renal failure requires reversal of muscle relaxation induced by vecuronium. Which of the following drugs is appropriate for this purpose?

A. Physostigmine
B. Rivastigmine
C. Sugammadex (Correct Answer)
D. Succinylcholine

Explanation: ***Sugammadex*** - **Sugammadex** is a modified gamma-cyclodextrin that forms a tight, water-soluble complex with **steroidal non-depolarizing neuromuscular blocking agents** like vecuronium, effectively encapsulating and inactivating them. - Its elimination is primarily renal, but even in **mild to moderate renal failure**, its rapid binding to vecuronium and lack of active metabolites make it a safe and effective choice for reversal. *Physostigmine* - **Physostigmine** is an anticholinesterase that indirectly increases acetylcholine at the neuromuscular junction, but it is not commonly used for reversing **neuromuscular blockade** due to its widespread muscarinic and nicotinic effects. - It can cause significant side effects like **bradycardia**, **bronchospasm**, and increased secretions, and its efficacy for non-depolarizing blockers is limited. *Rivastigmine* - **Rivastigmine** is an **acetylcholinesterase inhibitor** primarily used in the treatment of **Alzheimer's disease** and Parkinson's disease dementia. - It does not have a role in reversing neuromuscular blockade induced by vecuronium. *Succinylcholine* - **Succinylcholine** is a **depolarizing neuromuscular blocker** itself, causing muscle relaxation rather than reversing it. - It would prolong paralysis rather than reverse the effects of vecuronium.

Question 493: Arrange the following anesthetic agents based on their potency Nitrous oxide Halothane Isoflurane Methoxyflurane

A. Methoxyflurane > Halothane > Isoflurane > Nitrous oxide (Correct Answer)
B. Methoxyflurane > Nitrous oxide > Halothane > Isoflurane
C. Methoxyflurane > Isoflurane > Halothane > Nitrous oxide
D. Halothane > Isoflurane > Nitrous oxide > Methoxyflurane

Explanation: ***Methoxyflurane > Halothane > Isoflurane > Nitrous oxide*** - Anesthetic potency is inversely related to its **MAC (Minimum Alveolar Concentration)** value. A lower MAC value indicates higher potency. - The MAC values for these agents are: Methoxyflurane (0.16%), Halothane (0.75%), Isoflurane (1.15%), and Nitrous oxide (104%), which directly corresponds to this order of potency. *Methoxyflurane > Nitrous oxide > Halothane > Isoflurane* - This order incorrectly places nitrous oxide as more potent than halothane and isoflurane. **Nitrous oxide** has a very high MAC (104%), indicating low potency. - **Halothane** and **isoflurane** have significantly lower MAC values (0.75% and 1.15%, respectively), making them much more potent than nitrous oxide. *Methoxyflurane > Isoflurane > Halothane > Nitrous oxide* - This order incorrectly places **isoflurane** as more potent than halothane. **Halothane** has a MAC of 0.75%, while **isoflurane** has a MAC of 1.15%. - Therefore, halothane is more potent than isoflurane, making this sequence incorrect. *Halothane > Isoflurane > Nitrous oxide > Methoxyflurane* - This order incorrectly places **halothane** as the most potent and **methoxyflurane** as the least potent among the listed agents. - **Methoxyflurane** has the lowest MAC (0.16%), making it the most potent, while **nitrous oxide** has the highest MAC (104%), making it the least potent.

Question 494: Which of the following drugs is used for hypotensive anesthesia:

A. Both Isoflurane and Nitroglycerin (Correct Answer)
B. Isoflurane
C. Nitroglycerin
D. Dantrolene

Explanation: ***Both Isoflurane and Nitroglycerin*** - **Isoflurane** is a volatile anesthetic that can induce **hypotension** by decreasing systemic vascular resistance and myocardial contractility. - **Nitroglycerin** is a potent vasodilator that primarily acts on veins, but also on arteries, to reduce preload and afterload, thereby lowering blood pressure. *Isoflurane* - While **Isoflurane** can be used as part of a hypotensive anesthesia strategy, it is not the sole drug capable of achieving this effect. - Its hypotensive action is dose-dependent and results from **vasodilation** and direct **myocardial depression**. *Nitroglycerin* - **Nitroglycerin** is effective in inducing controlled **hypotension** due to its rapid onset and short duration of action as a vasodilator. - It is frequently used in anesthesia for its ability to reduce blood pressure, particularly in situations requiring a **dry surgical field**. *Dantrolene* - **Dantrolene** is a skeletal muscle relaxant primarily used to treat and prevent **malignant hyperthermia**. - It does not directly induce **hypotension** and is not indicated for hypotensive anesthesia.

Question 495: Which of the following is the most suitable anesthetic agent for use in dogs?

A. Propofol (Correct Answer)
B. Medetomidine hydrochloride
C. Ketamine
D. Midazolam

Explanation: ***Propofol*** - **Propofol** is a widely used and highly effective intravenous anesthetic in dogs due to its **rapid induction** and **rapid recovery**. - It produces minimal cumulative effects when administered as a constant rate infusion, making it suitable for both short procedures and maintenance of anesthesia. *Medetomidine hydrochloride* - **Medetomidine** is an **alpha-2 agonist** primarily used as a sedative and analgesic in dogs, not typically as the sole anesthetic agent for general anesthesia. - While it provides profound sedation, it is usually combined with other drugs (e.g., ketamine) to achieve surgical planes of anesthesia, and its effects on reducing heart rate and blood pressure can be significant. *Ketamine* - **Ketamine** is a **dissociative anesthetic** that provides good analgesia and somatic anesthesia but often causes muscle rigidity and can increase sympathetic tone. - It is typically used in combination with other sedatives or tranquilizers (e.g., diazepam, midazolam) to ensure smooth induction and recovery and prevent adverse effects like seizures. *Midazolam* - **Midazolam** is a **benzodiazepine** primarily used as a sedative, anxiolytic, and muscle relaxant, often as a premedicant or co-induction agent, not as a primary anesthetic for general anesthesia in dogs. - It offers minimal cardiovascular and respiratory depression when used alone, but it does not produce sufficient anesthetic depth for surgical procedures.

Question 496: Most preferred safe inducing agent in malignant hyperthermia-susceptible patients is

A. Halothane
B. Propofol (Correct Answer)
C. Thiopentone
D. Etomidate

Explanation: **Propofol** - Propofol is a **non-triggering agent** for malignant hyperthermia (MH) and is considered safe for use in susceptible patients. - It is a commonly used intravenous anesthetic that does not interfere with the **ryanodine receptor** (RyR1) or calcium homeostasis in skeletal muscle, which are central to MH pathophysiology. *Halothane* - Halothane is a **volatile anesthetic** that is a potent trigger for malignant hyperthermia. - It directly causes excessive calcium release from the **sarcoplasmic reticulum** in susceptible individuals, leading to uncontrolled muscle contraction and hypermetabolism. *Thiopentone* - Thiopentone, while an intravenous anesthetic, is still considered to have a **theoretical, albeit rare, risk** of triggering MH due to historical reports and its structural similarity to some triggers, though it's generally considered less risky than volatile agents. - However, newer, safer alternatives like propofol are preferred to completely avoid any potential risk in MH-susceptible patients. *Etomidate* - Etomidate is an intravenous anesthetic that is generally considered **safe** in malignant hyperthermia-susceptible patients as it also does not trigger the condition. - While safe, **propofol is often preferred** due to its more favorable pharmacokinetic profile for continuous infusion and broader applicability in induction and maintenance of anesthesia.

Question 497: Dose of ketamine by IM route is (in mg/kg) –

A. 10
B. 6
C. 4 (Correct Answer)
D. 8

Explanation: ***4*** - The standard recommended dose for **intramuscular (IM) administration of ketamine** for sedation or anesthesia induction is typically **4 mg/kg**. - This dose usually provides effective sedation and analgesia with a relatively rapid onset of action. *10* - A dose of **10 mg/kg IM ketamine** is generally considered too high for routine clinical use, increasing the risk of adverse effects such as **prolonged recovery, significant emergence reactions, and respiratory depression**. - This dose may be used in specific, carefully controlled situations, but it is not the standard initial dose. *6* - While **6 mg/kg IM ketamine** might be effective, it is on the higher side compared to the most commonly cited standard of 4 mg/kg. - Using a slightly lower standard dose like 4 mg/kg helps to minimize potential side effects, especially in patients who may be more sensitive to the drug. *8* - A dose of **8 mg/kg IM ketamine** is considerably higher than the typical recommended dose and would significantly increase the likelihood of **adverse effects** such as profound hallucinations, agitation, and cardiovascular stimulation. - Such high doses are not routinely used for IM administration in general practice.

Question 498: Effective adjuvant in attenuating hypertension and tachycardia associated with laryngoscopy and intubation?

A. Suxamethonium
B. Fentanyl (Correct Answer)
C. Ketamine
D. Atracurium

Explanation: ***Fentanyl*** - **Fentanyl**, a potent **opioid**, effectively blunts the **sympathetic response** associated with **laryngoscopy** and **intubation**, thereby reducing **hypertension** and **tachycardia**. - Its rapid onset and short duration of action make it a suitable **adjuvant** for this purpose. *Suxamethonium* - **Suxamethonium** is a **depolarizing neuromuscular blocker** used to facilitate intubation, not to attenuate the hemodynamic response. - It does not directly impact **blood pressure** or **heart rate** in a way that would mitigate the stress response. *Ketamine* - **Ketamine** can cause **sympathomimetic effects**, including **increased heart rate** and **blood pressure**, which would worsen rather than attenuate the hemodynamic response to intubation. - It is often used for its **dissociative anesthetic** properties, not for blunting the stress response. *Atracurium* - **Atracurium** is a **nondepolarizing neuromuscular blocker** used for muscle relaxation during intubation and surgery. - It does not directly affect **blood pressure** or **heart rate** in a manner that would attenuate the hypertensive and tachycardic response to laryngoscopy.

Question 499: Which muscle is most resistant to neuromuscular blockage?

A. Adductor pollicis
B. Ocular
C. Intercostal muscles
D. Diaphragm (Correct Answer)

Explanation: ***Diaphragm*** - The **diaphragm** is functionally resistant to neuromuscular blocking agents due to its high density of acetylcholine receptors and different isoform of nicotinic receptors. - Due to its vital role in respiration, it is the last muscle to be paralyzed and the first to recover from neuromuscular blockade. *Adductor pollicis* - The **adductor pollicis** is a commonly used muscle for monitoring neuromuscular blockade as it is highly sensitive to the effects of these agents. - Its response correlates well with the blockade of muscles in the **larynx and pharynx**, making it a good indicator for intubation conditions. *Ocular* - **Ocular muscles** are among the first muscles to be affected by neuromuscular blockers. - They tend to show partial recovery while other muscles are still significantly blocked, reflecting their high metabolic rate and sparse acetylcholine receptor distribution. *Intercostal muscles* - **Intercostal muscles** are accessory muscles of respiration that are more sensitive to neuromuscular blockade than the diaphragm. - They are paralyzed relatively early in the process and recover later than the diaphragm, leading to reduced tidal volume even when the diaphragm is functional.

Question 500: Which of the following anesthetic drugs is contraindicated in chronic renal failure?

A. Atracurium
B. Fentanyl
C. Pethidine (Correct Answer)
D. Morphine

Explanation: ***Pethidine*** - **Pethidine** is contraindicated in chronic renal failure due to its active metabolite, **normeperidine**, which is eliminated renally. - Accumulation of **normeperidine** can lead to **central nervous system (CNS) toxicity**, including seizures, tremors, and hyperreflexia. *Atracurium* - **Atracurium** undergoes **Hofmann elimination** and **ester hydrolysis**, which are independent of renal or hepatic function. - This makes it a relatively safe choice for patients with **renal impairment**. *Fentanyl* - **Fentanyl** is primarily metabolized by the liver, with its metabolites being inactive. - While some dose adjustment may be considered in severe renal failure, it is generally **safe** for use in patients with chronic renal impairment as its metabolites are inactive. *Morphine* - **Morphine** is metabolized in the liver to **morphine-3-glucuronide (M3G)** and **morphine-6-glucuronide (M6G)**, both of which are renally excreted. - **M6G** is an active metabolite with potent analgesic effects, and its accumulation in renal failure can cause **prolonged sedation** and **respiratory depression**. While significant caution and dose reduction are needed, it's not strictly contraindicated in the same way pethidine is due to the more neurotoxic nature of normeperidine.

Practice by Chapter

History of Anesthesia

Practice Questions

Preoperative Evaluation

Practice Questions

Pharmacology of Inhalational Anesthetics

Practice Questions

Pharmacology of Intravenous Anesthetics

Practice Questions

Neuromuscular Blocking Agents

Practice Questions

Airway Management

Practice Questions

Endotracheal Intubation

Practice Questions

Difficult Airway Algorithms

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Intraoperative Monitoring

Practice Questions

Depth of Anesthesia Monitoring

Practice Questions

Emergence from Anesthesia

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Postoperative Care

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