General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 221: Which of the following drugs undergoes Hoffman's elimination?

A. Atracurium (Correct Answer)
B. Pancuronium
C. Mivacurium
D. Vecuronium

Explanation: **Explanation:** **Atracurium** is the correct answer because it is a benzylisoquinolinium neuromuscular blocking agent specifically designed to undergo **Hofmann elimination**. This is a unique, non-enzymatic chemical degradation process that occurs at physiological pH and temperature. * **Mechanism:** In Hofmann elimination, the drug molecule breaks down spontaneously into inactive metabolites (laudanosine and monoquaternary acrylate). Because it does not rely on renal or hepatic function, Atracurium is the **drug of choice for patients with liver or kidney failure.** * **Cisatracurium**, an isomer of atracurium, also undergoes Hofmann elimination and is more potent with fewer side effects (less histamine release). **Why other options are incorrect:** * **Pancuronium:** A long-acting steroid-based muscle relaxant primarily excreted unchanged by the **kidneys** (80%). * **Mivacurium:** A short-acting benzylisoquinolinium that is metabolized by **plasma cholinesterase** (pseudocholinesterase), similar to succinylcholine. * **Vecuronium:** An intermediate-acting steroid-based relaxant primarily metabolized and excreted by the **liver** (biliary excretion). **High-Yield Clinical Pearls for NEET-PG:** 1. **Laudanosine Toxicity:** The major metabolite of atracurium, laudanosine, can cross the blood-brain barrier. In high concentrations (e.g., prolonged infusions in ICU), it may act as a **CNS stimulant and trigger seizures.** 2. **Temperature & pH Dependency:** Hofmann elimination is accelerated by **alkalosis and hyperthermia**, while it is delayed by acidosis and hypothermia. 3. **Histamine Release:** Atracurium can cause significant histamine release, leading to flushing, hypotension, and bronchospasm. Cisatracurium is preferred if cardiovascular stability is critical.

Question 222: Lacrimation during anesthesia indicates which stage?

A. Stage I
B. Stage II
C. Stage III (Correct Answer)
D. Stage IV

Explanation: **Explanation:** The correct answer is **Stage III (Surgical Anesthesia)**. This question refers to **Guedel’s Classification**, which describes the clinical signs of anesthesia progression using volatile agents like ether. **Why Stage III is correct:** Stage III is divided into four planes. **Lacrimation (tearing)** is a hallmark sign of **Plane 1 of Stage III**. During this stage, the patient transitions from the excitement of Stage II into a state of surgical anesthesia. While the blink reflex is lost, the presence of tears indicates a relatively light plane of anesthesia. As the patient moves deeper into Plane 2 and 3, lacrimation typically ceases. **Analysis of Incorrect Options:** * **Stage I (Analgesia):** Extends from induction to loss of consciousness. Reflexes remain intact, but lacrimation is not a defining clinical sign here. * **Stage II (Excitement/Delirium):** Characterized by struggling, breath-holding, and irregular respiration. While autonomic activity is high, lacrimation is specifically used to titrate depth within Stage III. * **Stage IV (Medullary Paralysis):** This is the stage of overdose. It is characterized by respiratory failure and vasomotor collapse. Lacrimation is absent as all reflex activities are abolished. **High-Yield Clinical Pearls for NEET-PG:** * **Guedel’s Stages** were originally described for **Diethyl Ether**; they are less distinct with modern intravenous agents (like Propofol) due to their rapid onset. * **Stage II Danger:** This is the most hazardous stage due to the risk of laryngospasm, vomiting, and cardiac arrhythmias. * **Pupillary Signs:** Pupils are dilated in Stage II (sympathetic overactivity), constricted in Stage III Plane 1-2, and widely dilated in Stage IV (paralysis). * **Respiration:** Becomes regular and automatic at the onset of Stage III.

Question 223: Which agent is known to cause muscle rigidity?

A. Fentanyl (Correct Answer)
B. Halothane
C. Ketamine
D. Droperidol

Explanation: **Explanation:** **Correct Option: A. Fentanyl** Fentanyl, a potent synthetic opioid, is well-known for causing **"Wooden Chest Syndrome"** (thoracic and abdominal wall muscle rigidity). This occurs primarily when high doses are administered via rapid intravenous bolus. The mechanism is attributed to the activation of opioid receptors in the central nervous system (specifically the striatum and nucleus accumbens), which increases efferent motor nerve activity. This rigidity can make manual ventilation extremely difficult and may require the administration of a neuromuscular blocking agent (like Succinylcholine) or an opioid antagonist (Naloxone) to reverse. **Incorrect Options:** * **B. Halothane:** This is an inhalational anesthetic that typically causes **muscle relaxation**. However, it is a potent trigger for Malignant Hyperthermia (MH) in genetically susceptible individuals, which presents with rigidity, but it is not the primary pharmacological effect of the drug itself. * **C. Ketamine:** While Ketamine increases muscle tone (hypertonicity) and may cause purposeless movements, it does not typically produce the severe, generalized truncal rigidity characteristic of high-dose opioids. * **D. Droperidol:** A butyrophenone derivative that can cause extrapyramidal side effects (like dystonia) due to dopamine blockade, but it is not the classic agent associated with acute intraoperative muscle rigidity. **High-Yield Clinical Pearls for NEET-PG:** * **Wooden Chest Syndrome:** Most common with Fentanyl, Sufentanil, and Alfentanil. * **Management:** The definitive treatment for fentanyl-induced rigidity is a rapid-acting muscle relaxant (Succinylcholine). * **Context:** Often tested in the context of "Induction of Anesthesia" or "Opioid Side Effects." * **Other Opioid Side Effects:** Pinpoint pupil (miosis), respiratory depression, and truncal rigidity.

Question 224: Which anesthetic agent is known for providing a smooth induction?

A. Diethyl ether
B. Thiopental (Correct Answer)
C. Nitrous oxide
D. Halothane

Explanation: **Explanation:** **Thiopental (Option B)** is the correct answer because it is a classic intravenous induction agent known for its rapid onset and smooth transition to unconsciousness. As an ultra-short-acting barbiturate, it crosses the blood-brain barrier almost instantly (within one arm-brain circulation time, approx. 10–20 seconds). It provides a "smooth" induction because it lacks the airway irritation, excitatory movements, or prolonged excitement phase (Stage II of anesthesia) often seen with older inhalational agents. **Analysis of Incorrect Options:** * **Diethyl ether (Option A):** Known for a very slow and unpleasant induction. It is highly pungent, irritates the respiratory mucosa, and causes a prolonged "Stage of Delirium" (Stage II), leading to struggling and secretions. * **Nitrous oxide (Option C):** While non-irritant, it has a low potency (MAC of 104%) and cannot produce surgical anesthesia or a complete induction when used alone. It is primarily used as an adjuvant. * **Halothane (Option D):** Although it was the gold standard for smooth *inhalational* induction in pediatrics due to its pleasant smell, it is slower than intravenous agents like Thiopental. In the context of general "smooth induction" without specifying the route, IV agents are superior. **High-Yield Clinical Pearls for NEET-PG:** * **Thiopental:** The drug of choice for rapid sequence induction (RSI) in patients without cardiovascular compromise. It is contraindicated in **Porphyria** (induces ALA synthetase). * **Redistribution:** The short duration of action of Thiopental is due to redistribution from the brain to muscle and fat, not metabolism. * **Gold Standard Shift:** While Thiopental was the traditional answer, **Propofol** has largely replaced it in modern practice due to a better safety profile and rapid clearance.

Question 225: Which of the following inducing agents is preferred for Electroconvulsive Therapy?

A. Thiopentone
B. Etomidate
C. Methohexital (Correct Answer)
D. Ketamine

Explanation: **Explanation:** The primary goal of anesthesia for **Electroconvulsive Therapy (ECT)** is to provide rapid induction and recovery while ensuring a **seizure duration** sufficient for therapeutic efficacy (typically >25 seconds). **Why Methohexital is the Correct Answer:** **Methohexital** (an ultra-short-acting barbiturate) is the **gold standard** and drug of choice for ECT. Unlike most other induction agents, it has a minimal inhibitory effect on seizure activity. It provides a rapid onset, quick recovery, and, most importantly, **prolongs seizure duration** more effectively than thiopentone, ensuring the procedure remains therapeutically beneficial. **Analysis of Incorrect Options:** * **Thiopentone (A):** While frequently used in the past, it has significant anticonvulsant properties which can shorten seizure duration, potentially reducing the clinical effectiveness of ECT. * **Etomidate (B):** It is known to prolong seizure duration even more than methohexital and is hemodynamically stable. However, it is associated with a higher incidence of post-ictal confusion, nausea, and myoclonus, making it a second-line choice. * **Ketamine (D):** It has pro-convulsant properties and can increase seizure duration. However, it is generally avoided as a first-line agent due to sympathetic stimulation (tachycardia/hypertension) and the risk of emergence delirium. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol** is generally avoided in ECT because it significantly **shortens seizure duration** (potent anticonvulsant). * **Succinylcholine** is the preferred muscle relaxant for ECT to prevent musculoskeletal injuries during the seizure. * **Physiological changes during ECT:** Initial **parasympathetic** surge (bradycardia/salivation) followed by a **sympathetic** surge (tachycardia/hypertension). * **Absolute Contraindication for ECT:** Increased intracranial pressure (ICP).

Question 226: Which neuromuscular blocker does not require reversal by neostigmine at the end of an operation?

A. d–Tubocurarine
B. Doxacurium
C. Pipecuronium
D. Mivacurium (Correct Answer)

Explanation: **Explanation:** The correct answer is **Mivacurium**. The requirement for reversal with an anticholinesterase like neostigmine depends on the duration of action and the metabolism of the neuromuscular blocking agent (NMBA). **1. Why Mivacurium is correct:** Mivacurium is a **short-acting** non-depolarizing NMBA. Its unique pharmacokinetic profile is characterized by rapid metabolism by **plasma cholinesterase (pseudocholinesterase)**, the same enzyme that degrades succinylcholine. Because of its very short half-life (approximately 2–3 minutes) and spontaneous, rapid recovery (within 15–20 minutes), pharmacological reversal with neostigmine is often unnecessary unless an immediate termination of block is required. **2. Why the other options are incorrect:** * **d–Tubocurarine:** A long-acting NMBA that is primarily excreted by the kidneys. It requires active reversal to ensure adequate respiratory effort post-surgery. * **Doxacurium:** A potent, long-acting benzylisoquinolinium compound. It has a slow onset and a very long duration of action, necessitating reversal. * **Pipecuronium:** A long-acting aminosteroid NMBA. Like other long-acting agents, it carries a high risk of residual neuromuscular blockade if not reversed. **3. Clinical Pearls for NEET-PG:** * **Metabolism:** Mivacurium is the only non-depolarizing NMBA metabolized by plasma cholinesterase. * **Hoffman Elimination:** Remember that **Atracurium** and **Cisatracurium** undergo organ-independent elimination (Hoffman elimination), making them ideal for patients with renal or hepatic failure. * **Side Effects:** Mivacurium can cause significant **histamine release**, leading to hypotension and flushing if injected rapidly. * **Prolonged Block:** Patients with **atypical plasma cholinesterase** (dibucaine number <30) will experience a significantly prolonged block with Mivacurium, similar to succinylcholine apnea.

Question 227: Volatile inhalational anesthetics contribute to which of the following components of general anesthesia, except?

A. Loss of consciousness
B. Loss of reflex
C. Analgesia (Correct Answer)
D. Muscle relaxation

Explanation: **Explanation:** General anesthesia is defined as a reversible state of drug-induced unconsciousness consisting of four primary components: **Amnesia/Hypnosis (Unconsciousness), Analgesia, Muscle Relaxation, and Reflex Suppression.** While volatile inhalational anesthetics (e.g., Sevoflurane, Isoflurane, Desflurane) are potent hypnotics, they are **poor analgesics**. At clinical concentrations, they do not provide sufficient pain relief to suppress the surgical stress response. Therefore, they must be supplemented with opioids (like Fentanyl) or regional blocks to achieve the "Analgesia" component of the anesthetic triad. **Analysis of Options:** * **Loss of Consciousness (A):** This is the primary effect of volatile agents. They act on GABA-A receptors and various ion channels in the brain to induce a state of hypnosis and amnesia. * **Loss of Reflex (B):** Volatile agents effectively suppress autonomic and motor responses to noxious stimuli, contributing to the stability of the patient during surgery. * **Muscle Relaxation (D):** Inhalational agents produce dose-dependent skeletal muscle relaxation by acting on the spinal cord and potentiating the effects of neuromuscular blocking agents. * **Analgesia (C):** As noted, volatile agents lack significant analgesic properties. Nitrous Oxide ($N_2O$) is the only common inhalational agent that provides significant analgesia, but it is a gas, not a volatile liquid. **High-Yield NEET-PG Pearls:** * **MAC (Minimum Alveolar Concentration):** A measure of potency; it specifically measures the concentration required to prevent movement (reflex) in 50% of patients, not analgesia. * **Nitrous Oxide Exception:** Unlike volatile agents, $N_2O$ has strong analgesic properties but is a weak hypnotic (MAC > 100%). * **Ketamine:** The only induction agent that provides all three: Unconsciousness, Analgesia, and Sympathetic stimulation.

Question 228: Who was the dentist who first used nitrous oxide for the abolition of pain during dental extraction?

A. David Harper
B. William Harvey
C. Horace Wells (Correct Answer)
D. John Hunter

Explanation: **Explanation:** **Horace Wells (Option C)** is the correct answer. In **1844**, Wells, an American dentist, observed the analgesic effects of **Nitrous Oxide** (Laughing Gas) during a public demonstration by Gardner Colton. He subsequently used it on himself for a painless tooth extraction performed by John Riggs. Although his public demonstration at Massachusetts General Hospital in 1845 was deemed a "humbug" because the patient cried out, Wells is historically recognized as the pioneer who first applied nitrous oxide for surgical anesthesia. **Analysis of Incorrect Options:** * **David Harper (Option A):** Not a significant figure in the history of anesthesia. * **William Harvey (Option B):** A famous English physician known for describing the **systemic circulation** of blood (1628), predating modern anesthesia by centuries. * **John Hunter (Option D):** A renowned 18th-century Scottish surgeon and anatomist known as the "Father of Modern Surgery," but he was not involved in the discovery of anesthetic gases. **High-Yield Clinical Pearls for NEET-PG:** * **William T.G. Morton:** A student of Wells who successfully demonstrated **Diethyl Ether** (Letheon) at the "Ether Dome" in 1846. * **James Young Simpson:** First used **Chloroform** for obstetric analgesia (1847). * **Joseph Priestley:** The chemist who discovered Nitrous Oxide in 1772. * **Nitrous Oxide Properties:** It has a low blood-gas partition coefficient (0.47), leading to rapid induction and recovery. It is known for the **"Second Gas Effect"** and **"Diffusion Hypoxia"** (Fink effect).

Question 229: Which muscle relaxant is associated with increased intracranial pressure?

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

Explanation: **Explanation:** **Suxamethonium (Succinylcholine)** is the correct answer because it is a depolarizing neuromuscular blocker that causes a transient increase in intracranial pressure (ICP). The underlying mechanism is attributed to two factors: 1. **Fasciculations:** The initial muscle contractions lead to an increase in central venous pressure and a surge in afferent muscle spindle activity, which increases cerebral blood flow. 2. **Cerebral Vasodilation:** It causes a mild increase in cerebral metabolic rate and blood flow, further elevating ICP. While this increase is usually transient and clinically insignificant in healthy patients, it can be critical in patients with pre-existing intracranial hypertension (e.g., brain tumors or head injury). **Analysis of Incorrect Options:** * **Atracurium & Mivacurium:** These are benzylisoquinolinium non-depolarizing relaxants. While they can cause histamine release (which may lead to systemic hypotension and a compensatory increase in cerebral blood flow), they do not directly increase ICP. In fact, they are often preferred in neurosurgery if hemodynamics are stable. * **Vecuronium:** This is an aminosteroid non-depolarizing relaxant known for its cardiovascular stability. It has no effect on ICP, making it a safe choice for neurosurgical procedures. **High-Yield Clinical Pearls for NEET-PG:** * **Pre-curarization:** The rise in ICP caused by Suxamethonium can be blunted by administering a small "defasciculating" dose of a non-depolarizing muscle relaxant (e.g., Vecuronium) 3 minutes prior. * **Other Pressures:** Suxamethonium also increases **Intraocular Pressure (IOP)** and **Intragastric Pressure (IGP)**. * **Contraindication:** Avoid Suxamethonium in patients with burns, crush injuries, or upper motor neuron lesions due to the risk of **hyperkalemia**.

Question 230: Relative contraindications for the administration of ketamine hydrochloride include all of the following EXCEPT?

A. Age < 5 years
B. History of epilepsy
C. Raised intracranial tension
D. Recent anterior myocardial infarction (Correct Answer)

Explanation: **Explanation:** The question asks to identify which option is **NOT** a relative contraindication for Ketamine. In clinical practice, a **Recent Myocardial Infarction (MI)** is considered an **Absolute Contraindication**, not a relative one. **1. Why "Recent Anterior Myocardial Infarction" is the correct answer:** Ketamine is a sympathomimetic agent. It causes a significant increase in heart rate, cardiac output, and arterial blood pressure by inhibiting the neuronal reuptake of catecholamines. In a patient with a recent MI, these effects drastically increase **myocardial oxygen demand**, which can lead to ischemia, extension of the infarct, or fatal arrhythmias. Therefore, it is strictly avoided (Absolute Contraindication). **2. Analysis of Incorrect Options (Relative Contraindications):** * **Age < 5 years:** While not strictly forbidden, Ketamine is used with caution in very young children due to the risk of laryngospasm and increased secretions. * **History of Epilepsy:** Ketamine has complex effects on the CNS. While it has some anticonvulsant properties, it can also lower the seizure threshold and induce epileptiform activity on EEG in susceptible individuals. * **Raised Intracranial Tension (ICT):** Traditionally, Ketamine was contraindicated in head injuries because it increases cerebral blood flow (CBF) and cerebral metabolic rate ($CMRO_2$), potentially worsening ICT. However, recent evidence suggests it may be used if the patient is well-ventilated, making it a relative rather than absolute contraindication. **Clinical Pearls for NEET-PG:** * **Drug of Choice:** Ketamine is the induction agent of choice for **Hypovolemic/Hemorrhagic Shock** and **Bronchial Asthma** (due to its bronchodilatory properties). * **Dissociative Anesthesia:** It acts primarily on **NMDA receptors**, causing a state where the patient appears awake but is unconscious (eyes open, slow nystagmic gaze). * **Side Effect:** **Emergence Delirium** (hallucinations) is a common side effect, which can be mitigated by pre-treating with Benzodiazepines (e.g., Midazolam).

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

Practice Questions

Intraoperative Monitoring

Practice Questions

Depth of Anesthesia Monitoring

Practice Questions

Emergence from Anesthesia

Practice Questions

Postoperative Care

Practice Questions

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