General Anesthesia Practice Questions

Q: Which of the following is a short-acting, non-depolarizing muscle relaxant?

Mivacurium. **Explanation:** Muscle relaxants (Neuromuscular Blocking Agents) are primarily classified based on their duration of action. **Mivacurium** is the correct answer because it is the only **short-acting** non-depolarizing neuromuscular blocker (NDNMB) currently used in clinical practice. **1. Why Mivacurium is correct:** Mivacurium belongs to the benzylisoquinolone class. Its short duration of action (approximately 15–20 minutes) is due to its rapid metabolism by **plasma cholinesterase** (pseudocholinesterase), similar to succinylcholine. This makes it unique among non-depolarizing agents, which typically rely on organ-based elimination. **2. Analysis of Incorrect Options:** * **Doxacuronium & Pipecurium:** These are **long-acting** NDNMBs. They have a slow onset and a prolonged duration of action (usually >60 minutes), making them less ideal for short procedures. * **Vecuronium:** This is an **intermediate-acting** aminosteroid NDNMB. Its duration of action typically ranges from 30 to 45 minutes. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Since Mivacurium is metabolized by plasma cholinesterase, its action is significantly prolonged in patients with **atypical plasma cholinesterase deficiency**. * **Side Effect:** Mivacurium is notorious for causing **histamine release**, which can lead to cutaneous flushing, hypotension, and bronchospasm if injected rapidly. * **Classification Summary:** * *Short-acting:* Mivacurium. * *Intermediate-acting:* Vecuronium, Rocuranium, Atracurium, Cisatracurium. * *Long-acting:* Pancuronium, Doxacuronium, Pipecurium. * **Rocuronium** is the NDNMB with the fastest onset of action, often used as an alternative to succinylcholine for rapid sequence induction.

Q: Which of the following statements is true about Halothane?

Vasodilator. **Explanation:** **Halothane** is a potent volatile anesthetic agent. The correct answer is **Vasodilator** because Halothane causes a dose-dependent reduction in arterial blood pressure. This occurs through two primary mechanisms: direct myocardial depression (reducing cardiac output) and **peripheral vasodilation** (reducing systemic vascular resistance). **Analysis of Options:** * **A. Non-irritant:** While Halothane is relatively non-pungent compared to Isoflurane or Desflurane (making it suitable for mask induction in pediatrics), it is technically considered a mild irritant to the respiratory mucosa compared to Sevoflurane, which is the gold standard for non-irritant induction. * **B. Antiarrhythmic:** This is incorrect. Halothane is famously **arrhythmogenic**. It sensitizes the myocardium to the effects of circulating catecholamines (epinephrine), which can lead to ventricular arrhythmias. * **C. It antagonizes bronchospasm:** While Halothane is a potent bronchodilator, the phrasing "antagonizes bronchospasm" is less accurate than its direct physiological effect of smooth muscle relaxation. More importantly, in the context of this specific question, its systemic **vasodilatory** effect is a more definitive pharmacological property. **High-Yield Clinical Pearls for NEET-PG:** * **Halothane Hepatitis:** A rare but serious immune-mediated hepatotoxicity (Type II) occurring after repeat exposure. * **Malignant Hyperthermia:** Like all volatile agents, Halothane is a known trigger. * **"Halothane Shakes":** Post-operative shivering is common. * **Uterine Relaxation:** It causes significant uterine atony, which can increase postpartum hemorrhage (PPH) risk if used in obstetrics. * **Blood-Gas Partition Coefficient:** 2.4 (Slow induction and recovery).

Q: Which of the following is untrue about mivacurium?

Onset of action is early. **Explanation:** Mivacurium is a short-acting, non-depolarizing neuromuscular blocking agent (NMBA) belonging to the benzylisoquinolone class. **Why Option C is the correct answer (Untrue statement):** Despite being a short-acting drug, Mivacurium has a **slow onset of action** (approximately 2–4 minutes). In contrast, Succinylcholine (a depolarizing agent) has a very rapid onset (30–60 seconds). For NEET-PG, it is vital to remember that "short duration" does not equate to "rapid onset." Mivacurium is not suitable for Rapid Sequence Induction (RSI). **Analysis of other options (True statements):** * **A. Metabolized by pseudocholinesterase:** Like succinylcholine, mivacurium is hydrolyzed by plasma cholinesterase (pseudocholinesterase). Its action is significantly prolonged in patients with atypical plasma cholinesterase deficiency. * **B. Releases histamine:** As a benzylisoquinolone, mivacurium can cause mast cell degranulation leading to histamine release, which may manifest as cutaneous flushing, hypotension, or bronchospasm, especially if injected rapidly. * **D. Short duration of action:** It has the shortest duration among all non-depolarizing NMBAs (approx. 12–20 minutes), making it ideal for short surgical procedures. **High-Yield Clinical Pearls for NEET-PG:** 1. **Metabolism:** It is the only non-depolarizing muscle relaxant metabolized by pseudocholinesterase. 2. **Reversal:** Spontaneous recovery is rapid; however, it can be reversed with neostigmine, though this is rarely required. 3. **Edrophonium:** Interestingly, edrophonium is preferred over neostigmine for reversal as it does not inhibit pseudocholinesterase as strongly as neostigmine does. 4. **Rapacuronium:** This was a non-depolarizing agent with a rapid onset, but it was withdrawn due to severe bronchospasm. Currently, **Rocuronium** is the non-depolarizing agent with the fastest onset.

Q: Which of the following drugs helps in the rapid reversal of the effect of rocuronium?

Sugammadex. **Explanation:** **Sugammadex** is the correct answer as it is a selective relaxant binding agent (SRBA) specifically designed for the rapid reversal of steroidal non-depolarizing neuromuscular blocking agents (NMBAs), primarily **Rocuronium** and Vecuronium. **Mechanism of Action:** Sugammadex is a modified $\gamma$-cyclodextrin. Its structure resembles a hollow "doughnut" that encapsulates the rocuronium molecule in the plasma, forming a stable 1:1 complex. This creates a concentration gradient that pulls rocuronium away from the nicotinic receptors at the neuromuscular junction back into the plasma, leading to a rapid and complete reversal of blockade, even if the block is deep. **Why other options are incorrect:** * **Neostigmine:** An acetylcholinesterase inhibitor. It increases the concentration of acetylcholine at the synapse to outcompete the NMBA. It is slower than Sugammadex and has a "ceiling effect," meaning it cannot reverse a deep block effectively. * **Edrophonium:** A short-acting acetylcholinesterase inhibitor primarily used for the diagnosis of Myasthenia Gravis (Tensilon test), not for the routine rapid reversal of rocuronium. * **Atropine:** An anticholinergic drug. It does not reverse muscle relaxants; it is co-administered with neostigmine to prevent bradycardia and excessive secretions caused by muscarinic stimulation. **High-Yield Clinical Pearls for NEET-PG:** * **Dosing:** 2 mg/kg for routine reversal (TOF 2); 4 mg/kg for deep block (PTC 1-2); 16 mg/kg for immediate reversal after a 1.2 mg/kg dose of rocuronium. * **Side Effects:** Anaphylaxis (rare but significant) and interference with hormonal contraceptives (patients should be advised to use backup contraception for 7 days). * **Excretion:** It is excreted unchanged by the kidneys; use with caution in severe renal impairment.

Q: Which inhalational anesthetic agent possesses analgesic properties?

Xenon. **Explanation** The correct answer is **Xenon**. **1. Why Xenon is Correct:** Most volatile inhalational anesthetics (like the "fluranes") provide unconsciousness and muscle relaxation but lack significant intrinsic analgesic properties. Xenon is unique because its primary mechanism of action involves the **non-competitive inhibition of NMDA (N-methyl-D-aspartate) receptors**. Since NMDA receptors are heavily involved in pain transmission and central sensitization, their inhibition provides potent **analgesia** along with anesthesia. Nitrous Oxide ($N_2O$) is the only other commonly discussed inhalational agent with significant analgesic properties, also via NMDA antagonism. **2. Why the Other Options are Incorrect:** * **Desflurane, Isoflurane, and Sevoflurane:** These are halogenated ethers. Their primary mechanism involves modulating **GABA-A receptors** and glycine receptors. While they produce a dose-dependent depression of the CNS (hypnosis), they do not provide effective analgesia. In fact, at sub-anesthetic concentrations, some volatile agents can be "hyperalgesic" (increasing sensitivity to pain). **3. High-Yield Clinical Pearls for NEET-PG:** * **Ideal Anesthetic:** Xenon is often called the "ideal anesthetic" because it is non-explosive, non-toxic, chemically inert, and provides rapid induction/recovery due to an extremely low **blood-gas partition coefficient (0.115)**. * **MAC Value:** The MAC of Xenon is approximately **63–71%**, making it less potent than halogenated agents but more potent than $N_2O$. * **Cardiovascular Stability:** Unlike the "fluranes," Xenon is remarkably cardio-stable and does not depress myocardial contractility. * **Environmental Impact:** It is an expensive noble gas but is environmentally friendly (no greenhouse effect), unlike $N_2O$ or Desflurane.

Q: Intra-arterial injection of thiopentone causes which of the following?

Vasospasm. **Explanation:** Accidental intra-arterial injection of **Thiopentone sodium** is a known anesthetic emergency. Thiopentone is highly alkaline (pH 10.5). When injected into an artery, it reacts with the blood to form **crystals**, which trigger an intense inflammatory response and the release of **norepinephrine** from perivascular nerve endings. 1. **Why Vasospasm is Correct:** The primary and immediate pathological response to intra-arterial thiopentone is **intense vasospasm**. This is mediated by the local release of catecholamines and the mechanical irritation caused by crystal precipitation. This spasm leads to severe pain (often described as a "burning" sensation) and distal ischemia. 2. **Why other options are incorrect:** * **Vasodilation:** Thiopentone causes the opposite effect (vasoconstriction/spasm) in arteries. * **Necrosis of the vessel wall:** While prolonged ischemia can lead to gangrene of the distal limb, the immediate effect is vasospasm. Necrosis is a late complication, not the primary mechanism. * **Hypotension:** While thiopentone causes systemic hypotension when given intravenously (due to myocardial depression and peripheral venodilation), an intra-arterial injection causes localized hypertensive/ischemic effects in the affected limb. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Severe pain, blanching of the limb, and loss of distal pulses. * **Management Protocol:** 1. **Leave the needle in situ:** To administer drugs through the same port. 2. **Dilute the drug:** Inject Normal Saline. 3. **Relieve Vasospasm:** Inject **Papaverine** (drug of choice), Lidocaine, or Priscoline. 4. **Sympathetic Block:** Stellate ganglion block or Brachial plexus block to promote vasodilation. 5. **Anticoagulation:** Heparin to prevent secondary thrombosis.

Q: Which muscles are the first to recover after administration of muscle relaxants?

Diaphragm. **Explanation:** The sensitivity of muscles to neuromuscular blocking agents (NMBAs) follows a predictable pattern based on muscle fiber type, blood flow, and the density of acetylcholine receptors. **1. Why the Diaphragm is Correct:** The **diaphragm** is the most resistant muscle to NMBAs and is the **first to recover** from a neuromuscular block. This is due to its high density of acetylcholine receptors and its central location, which ensures high regional blood flow, allowing for rapid delivery and subsequent washout of the relaxant. Conversely, because it is resistant, the diaphragm is also the **last to be paralyzed** during induction. **2. Analysis of Incorrect Options:** * **Laryngeal muscles (A):** These recover after the diaphragm but before the peripheral muscles. They are relatively resistant but not as much as the diaphragm. * **Abdominal muscles (B):** These are intermediate in sensitivity. They are paralyzed after the diaphragm but before the small muscles of the hand. * **Thenar muscles (D):** These are peripheral muscles (like the adductor pollicis). Peripheral muscles are the **first to be paralyzed** and the **last to recover**. This is why monitoring the adductor pollicis with a nerve stimulator is a "safe" indicator; if the thumb has recovered, the diaphragm has certainly recovered. **3. High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Paralysis:** Small muscles (eyes/fingers) → Limbs → Trunk (Abdomen) → Intercostals → Diaphragm. * **Sequence of Recovery:** Exactly the reverse (Diaphragm recovers first; Eye muscles recover last). * **Monitoring Tip:** To monitor **onset** (intubation readiness), the orbicularis oculi is preferred (reflects the diaphragm). To monitor **recovery** (extubation readiness), the adductor pollicis is preferred (reflects the return of airway protection).

Q: Which of the following is the muscle relaxant of choice in renal failure?

Atracurium. **Explanation:** The muscle relaxant of choice in renal failure is **Atracurium** (or its isomer, Cisatracurium). **1. Why Atracurium is the Correct Choice:** Most neuromuscular blocking agents (NMBAs) rely on renal or hepatic excretion for clearance. In renal failure, these drugs accumulate, leading to prolonged paralysis. Atracurium is unique because it undergoes **Hofmann Elimination**—a spontaneous, non-enzymatic degradation at physiological pH and temperature—and ester hydrolysis. Since its metabolism is independent of organ function, its duration of action remains unchanged in patients with end-stage renal disease (ESRD). **2. Why the Other Options are Incorrect:** * **Pancuronium:** This is a long-acting NMBA primarily excreted by the kidneys (approx. 80%). It is strictly contraindicated in renal failure due to the high risk of profound, prolonged neuromuscular blockade. * **Rocuronium:** It is primarily eliminated by the liver, but a significant portion (up to 30%) is excreted unchanged in the urine. Its duration of action is unpredictable and often prolonged in renal failure. * **Rapacurium:** This was a rapid-onset agent withdrawn from the market worldwide due to a high incidence of severe bronchospasm. **Clinical Pearls for NEET-PG:** * **Cisatracurium** is more potent than atracurium and is often preferred because it produces less **laudanosine** (a metabolite that can cause seizures) and does not cause histamine release. * **Vecuronium** is mostly biliary-excreted but has an active metabolite (3-desacetyl vecuronium) that accumulates in renal failure. * **Sugammadex** (a reversal agent) is generally avoided in severe renal impairment because the sugammadex-rocuronium complex is cleared renally.

Question 1

Which of the following is a short-acting, non-depolarizing muscle relaxant?

Accepted Answer

Mivacurium

Answer

Doxacuronium

Answer

Pipecurium

Answer

Vecuronium

Question 2

Which of the following statements is true about Halothane?

Accepted Answer

Vasodilator

Answer

Non-irritant

Answer

Antiarrhythmic

Answer

It antagonizes bronchospasm

Question 3

Which of the following is untrue about mivacurium?

Accepted Answer

Onset of action is early

Answer

Metabolized by pseudocholinesterase

Answer

Releases histamine

Answer

Short duration of action

Question 4

Which of the following drugs helps in the rapid reversal of the effect of rocuronium?

Accepted Answer

Sugammadex

Answer

Neostigmine

Answer

Edrophonium

Answer

Atropine

Question 5

Which inhalational anesthetic agent possesses analgesic properties?

Accepted Answer

Xenon

Answer

Desflurane

Answer

Isoflurane

Answer

Sevoflurane

Question 6

Intra-arterial injection of thiopentone causes which of the following?

Accepted Answer

Vasospasm

Answer

Vasodilation

Answer

Necrosis of the vessel wall

Answer

Hypotension

Question 7

Nitrous oxide is contraindicated in patients with pneumothorax, pneumopericardium, or intestinal obstruction because it:

Accepted Answer

Causes the expansion of air-filled body cavities

Answer

Depresses an already compromised myocardium

Answer

Permits the use of a limited FIO2 only

Answer

Is less soluble than nitrogen

Question 8

Which of the following is NOT a characteristic of nondepolarizing neuromuscular blockers?

Accepted Answer

Shows fasciculations

Answer

Fade on train-of-four stimulation

Answer

Tetanic stimulation is followed by post-tetanic facilitation

Answer

Reversed by neostigmine

Question 9

Which muscles are the first to recover after administration of muscle relaxants?

Accepted Answer

Diaphragm

Answer

Laryngeal muscles

Answer

Abdominal muscles

Answer

Thenar muscles

Question 10

Which of the following is the muscle relaxant of choice in renal failure?

Accepted Answer

Atracurium

Answer

Rapacurium

Answer

Pancuronium

Answer

Rocuronium

General Anesthesia — MCQs

General Anesthesia — MCQs

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