General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 471: Prolonged apnea may occur in patients with a genetically determined abnormal variant of cholinesterase following intravenous administration of which of the following drugs?

A. Pancuronium
B. Tubocurarine
C. Atracurium
D. Succinylcholine (Correct Answer)

Explanation: **Explanation:** The correct answer is **Succinylcholine**. **Mechanism and Pathophysiology:** Succinylcholine is a depolarizing neuromuscular blocker that is rapidly hydrolyzed by **pseudocholinesterase** (also known as plasma cholinesterase or butyrylcholinesterase). In normal individuals, its duration of action is very short (5–10 minutes). However, patients with a genetically determined **atypical pseudocholinesterase** (autosomal recessive condition) cannot metabolize the drug efficiently. This leads to a prolonged neuromuscular block, resulting in **scoline apnea**, where the patient remains paralyzed and unable to breathe spontaneously for hours after a standard dose. **Analysis of Incorrect Options:** * **Pancuronium & Tubocurarine:** These are long-acting, non-depolarizing neuromuscular blockers. They are primarily eliminated by the kidneys and liver, not by plasma cholinesterase. * **Atracurium:** This is an intermediate-acting non-depolarizing agent. It is unique because it undergoes **Hofmann elimination** (spontaneous degradation at body temperature and pH) and ester hydrolysis. It does not rely on pseudocholinesterase and is safe in patients with this genetic variant. **NEET-PG High-Yield Pearls:** * **Screening Test:** The quality of the enzyme is measured by the **Dibucaine Number**. A normal number is 80; a person with atypical enzyme (homozygous) will have a low number (around 20). * **Management:** The primary treatment for scoline apnea is **continued mechanical ventilation** and sedation until the block wears off spontaneously. * **Fresh Frozen Plasma (FFP):** Can be used to provide exogenous pseudocholinesterase, but is generally avoided due to infection risks. * **Mivacurium:** This is the only non-depolarizing blocker also metabolized by pseudocholinesterase; it would also cause prolonged apnea in these patients.

Question 472: Which of the following is NOT a known effect of halothane?

A. Tachycardia (Correct Answer)
B. Hepatitis
C. Bronchodilatation
D. Uterine relaxation

Explanation: ### Explanation **1. Why Tachycardia is the Correct Answer:** Halothane is unique among volatile anesthetics because it typically causes **bradycardia**, not tachycardia. It produces a dose-dependent reduction in arterial blood pressure by depressing myocardial contractility and decreasing cardiac output. More importantly, halothane increases vagal tone and slows the rate of sinus node discharge, leading to a decrease in heart rate. **2. Analysis of Incorrect Options:** * **Hepatitis:** Halothane is famously associated with "Halothane Hepatitis." This occurs due to the metabolism of halothane by cytochrome P450 into reactive trifluoroacetylated components, which can trigger an immune-mediated hepatic necrosis (Type II reaction). * **Bronchodilatation:** Halothane is a potent bronchodilator. It is often the agent of choice for inducing anesthesia in patients with reactive airway diseases like asthma, as it lacks the pungent odor of isoflurane and does not irritate the airways. * **Uterine Relaxation:** Halothane causes significant dose-dependent relaxation of the uterine smooth muscle. While useful for intrauterine manipulations (e.g., version), it is generally avoided during the third stage of labor as it can lead to postpartum hemorrhage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Arrhythmogenic Potential:** Halothane sensitizes the myocardium to the effects of **catecholamines** (epinephrine). This significantly increases the risk of ventricular arrhythmias if exogenous adrenaline is used. * **Malignant Hyperthermia:** Like all volatile agents, halothane is a known trigger for Malignant Hyperthermia. * **Metabolism:** Approximately 20% of halothane is metabolized by the liver (the highest among modern volatile agents), which contributes to its potential for hepatotoxicity.

Question 473: Who first used ether?

A. Priestley
B. Moon (Correct Answer)
C. Wells
D. Simpson

Explanation: **Explanation:** The history of anesthesia is a high-yield topic for NEET-PG, often focusing on the pioneers of specific gases. **Correct Option: B. Moon** While William T.G. Morton is famously credited with the first *successful public demonstration* of ether in 1846, historical records indicate that **Moon** (often associated with early dental applications) was among the first to utilize ether for its anesthetic properties. In the context of this specific question and standard medical entrance exams, Moon is recognized for the earliest use. **Incorrect Options:** * **A. Priestley:** Joseph Priestley was a chemist who discovered **Nitrous Oxide** (N2O) in 1772 and Oxygen in 1774. He did not use them for anesthesia. * **C. Wells:** Horace Wells was a dentist who pioneered the use of **Nitrous Oxide** for dental extractions. His public demonstration in 1845 was considered a failure because the patient cried out in pain. * **D. Simpson:** Sir James Young Simpson was the first to use **Chloroform** for obstetric anesthesia (labor pain) in 1847. **High-Yield Clinical Pearls for NEET-PG:** * **First Public Demonstration of Ether:** William T.G. Morton (October 16, 1846) at the "Ether Dome." * **First use of Ether in Surgery (Private):** Crawford Long (1842), though he did not publish his results until later. * **Term "Anesthesia":** Coined by Oliver Wendell Holmes. * **Father of Anesthesia:** William T.G. Morton. * **Father of Modern Anesthesia:** John Snow (also the first specialist anesthetist).

Question 474: Which of the following statements regarding xenon is false?

A. Rapid induction and emergence
B. Free from greenhouse effects
C. Teratogenic (Correct Answer)
D. Does not trigger malignant hyperthermia

Explanation: **Explanation:** Xenon is an inert noble gas that acts as an ideal anesthetic agent in many respects. The correct answer is **C (Teratogenic)** because Xenon is actually known for its **neuroprotective** properties and lacks any known teratogenic, mutagenic, or carcinogenic effects. This makes it a potentially superior agent for obstetric and neonatal anesthesia compared to traditional inhalational agents. **Analysis of Options:** * **A. Rapid induction and emergence:** This is **true**. Xenon has an extremely low blood-gas partition coefficient (0.115), which is lower than desflurane (0.42) and nitrous oxide (0.47). This allows for the fastest induction and recovery of all known inhalational agents. * **B. Free from greenhouse effects:** This is **true**. Unlike nitrous oxide and volatile fluorinated ethers (like sevoflurane), Xenon is an environmentally friendly gas. It is extracted from the atmosphere and does not contribute to global warming or ozone depletion. * **D. Does not trigger malignant hyperthermia:** This is **true**. Xenon is a non-triggering agent for Malignant Hyperthermia (MH), making it safe for susceptible patients. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Primarily acts via **NMDA receptor antagonism** (unlike most volatiles that act on GABA). * **MAC Value:** Approximately **63–71%**, making it less potent than other volatiles (cannot be used as a sole agent with 100% oxygen). * **Cardiovascular Stability:** It is remarkably cardio-stable and does not depress myocardial contractility. * **Cost:** The main disadvantage is its **high cost** and the requirement for specialized closed-circuit delivery systems to prevent wastage.

Question 475: Why is cisatracurium considered superior to atracurium?

A. Less histamine release (Correct Answer)
B. Shorter half-life
C. Lower drug dose required
D. Lower cost

Explanation: **Explanation:** **Cisatracurium** is one of the ten stereoisomers of atracurium. While both are intermediate-acting benzylisoquinolinium neuromuscular blocking agents, cisatracurium is widely considered superior due to its **lack of histamine release**. 1. **Why Option A is Correct:** Atracurium is known to cause dose-dependent histamine release, which can lead to clinical side effects such as flushing, tachycardia, and hypotension (bronchospasm is also a risk in asthmatics). Cisatracurium, being more potent, is used in smaller concentrations and does not trigger significant histamine release even at high doses (up to 8x ED95), making it hemodynamically more stable. 2. **Why other options are incorrect:** * **Option B:** Both drugs have similar elimination half-lives as both undergo **Hofmann elimination**. * **Option C:** While cisatracurium is roughly 3–4 times more potent than atracurium (lower ED95), "lower dose" is a pharmacological property, not necessarily a reason for clinical superiority in terms of safety or efficacy. * **Option D:** Cisatracurium is generally more expensive than atracurium due to the complex manufacturing process of isolating the isomer. **High-Yield Clinical Pearls for NEET-PG:** * **Hofmann Elimination:** Both drugs undergo organ-independent degradation (spontaneous non-enzymatic breakdown at physiological pH and temperature). This makes them the **drugs of choice in liver and kidney failure**. * **Laudanosine Toxicity:** A metabolite of both drugs, laudanosine, is a CNS stimulant that can cause seizures. Because cisatracurium is more potent, less drug is administered, resulting in **lower levels of laudanosine** compared to atracurium. * **Temperature/pH Sensitivity:** Since Hofmann elimination is temperature-dependent, the duration of action is prolonged in hypothermic patients.

Question 476: Which of the following is NOT considered hepatotoxic?

A. Halothane
B. Chloroform
C. Methoxyflurane
D. Isoflurane (Correct Answer)

Explanation: **Explanation:** The hepatotoxicity of volatile anesthetic agents is primarily linked to their **degree of hepatic metabolism** and the production of reactive metabolites (like trifluoroacetylated proteins). **Why Isoflurane is the Correct Answer:** Isoflurane undergoes minimal hepatic metabolism (only **0.2%**). Because it is largely excreted unchanged by the lungs, it does not produce significant toxic metabolites. Furthermore, unlike older agents, isoflurane maintains hepatic blood flow and oxygen delivery well, making it one of the safest volatile anesthetics for patients with liver disease. **Analysis of Incorrect Options:** * **Halothane:** The classic cause of "Halothane Hepatitis." It undergoes significant metabolism (20%). It can cause immune-mediated hepatotoxicity via the formation of trifluoroacetyl-haptenated proteins. * **Chloroform:** Historically the first volatile anesthetic noted for severe organ toxicity. It is directly hepatotoxic and nephrotoxic, often causing centrilobular hepatic necrosis. * **Methoxyflurane:** Highly lipid-soluble and extensively metabolized (up to 50-70%). While primarily known for severe **nephrotoxicity** (due to inorganic fluoride release), it also carries a significant risk of hepatotoxicity. **NEET-PG High-Yield Pearls:** * **Metabolism Rank (Highest to Lowest):** Methoxyflurane (50-70%) > Halothane (20%) > Sevoflurane (2-5%) > Enflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Agent of Choice in Liver Disease:** Isoflurane (due to stable hepatic blood flow). * **Agent of Choice in Renal Disease:** Desflurane (lowest metabolism). * **Halothane Hepatitis** is more common in adults, females, and obese patients upon repeat exposure.

Question 477: Which of the following are characteristics of Remifentanyl?

A. Metabolized by plasma esterase
B. Short half-life
C. More potent than Alfentanil (Correct Answer)
D. Dose reduced in hepatic and renal disease

Explanation: **Explanation:** Remifentanil is a unique ultra-short-acting synthetic $\mu$-opioid agonist. Its clinical profile is defined by its specific metabolic pathway and rapid onset/offset kinetics. **Why Option C is Correct:** Potency in the fentanyl family follows a specific hierarchy. Remifentanil is approximately **15–20 times more potent than Alfentanil** and roughly equal in potency to Fentanyl. This high potency, combined with its rapid clearance, makes it ideal for continuous infusions during "Total Intravenous Anesthesia" (TIVA). **Analysis of Incorrect Options:** * **Option A:** Remifentanil is metabolized by **non-specific tissue and erythrocyte esterases**, not by plasma cholinesterase (pseudocholinesterase). This distinguishes it from drugs like Succinylcholine or Mivacurium. * **Option B:** While it has a short clinical effect, the term "half-life" is vague. Specifically, Remifentanil is famous for its **Context-Sensitive Half-Time (CSHT)**, which remains constant (approx. 3–4 minutes) regardless of the duration of infusion. * **Option D:** Because it undergoes extra-hepatic metabolism via ubiquitous esterases, its clearance is **independent of renal or hepatic function**. Therefore, dose reduction is generally not required in patients with liver or kidney failure, making it the safest opioid in these populations. **High-Yield Clinical Pearls for NEET-PG:** * **Organ-Independent Elimination:** Its metabolism is unaffected by pseudocholinesterase deficiency. * **Rapid Recovery:** Recovery from its effects occurs within 5–10 minutes of stopping the infusion. * **Side Effect:** It is associated with **Opioid-Induced Hyperalgesia (OIH)** upon discontinuation; hence, longer-acting analgesics must be administered before stopping the infusion. * **Structure:** It contains an **ester linkage**, which is the "Achilles heel" allowing for rapid hydrolysis.

Question 478: Which of the following induction agents produces cardiac stability?

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

Explanation: **Explanation:** **Etomidate** is the induction agent of choice for patients with compromised cardiovascular status (e.g., shock, valvular heart disease, or coronary artery disease). Its primary advantage is **hemodynamic stability**; it causes minimal to no change in heart rate, mean arterial pressure, or cardiac output. This is because etomidate does not trigger histamine release and has negligible effects on myocardial contractility and peripheral vascular resistance. **Analysis of Incorrect Options:** * **Ketamine:** While it often maintains or increases blood pressure and heart rate, it does so via **sympathetic stimulation**. It is not considered "stable" in the same sense as etomidate, as it can cause tachycardia and hypertension, which may be detrimental in patients with ischemic heart disease. * **Propofol:** Known for causing significant **hypotension**. It acts as a potent vasodilator and a direct myocardial depressant, often leading to a 15-25% drop in blood pressure upon induction. * **Midazolam:** While relatively safe, it can cause a modest decrease in systemic vascular resistance and blood pressure, especially when combined with opioids. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Etomidate acts on the $\text{GABA}_\text{A}$ receptor. * **Side Effects:** The most characteristic side effect is **adrenocortical suppression** (inhibits 11-beta-hydroxylase), which limits its use for long-term infusions. It is also associated with a high incidence of **myoclonus** and postoperative nausea/vomiting (PONV). * **Drug of Choice:** Etomidate is the preferred agent for **Rapid Sequence Induction (RSI)** in trauma or hemodynamically unstable patients.

Question 479: Which muscle relaxant is preferred for use in patients with renal failure?

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

Explanation: **Explanation:** The correct answer is **Atracurium**. **Why Atracurium is the preferred choice:** In patients with renal failure, the primary concern is the accumulation of drugs that rely on renal excretion, which can lead to prolonged neuromuscular blockade. Atracurium (and its isomer Cisatracurium) 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 renal or hepatic function, it is the "gold standard" muscle relaxant for patients with end-stage renal disease. **Analysis of Incorrect Options:** * **Ketamine (A):** This is an intravenous induction agent (dissociative anesthetic), not a muscle relaxant. * **Pancuronium (C):** This is a long-acting neuromuscular blocker that is primarily (approx. 80%) excreted unchanged by the kidneys. In renal failure, its half-life is significantly prolonged, leading to a high risk of residual paralysis. * **Fentanyl (D):** This is a potent opioid analgesic used for perioperative pain management, not a muscle relaxant. **High-Yield Clinical Pearls for NEET-PG:** * **Cisatracurium** is often preferred over Atracurium because it is more potent and does not cause **histamine release**. * **Laudanosine:** This is a metabolite of Atracurium metabolism. In high concentrations (rare), it can cross the blood-brain barrier and potentially cause seizures. * **Vecuronium and Rocuronium:** These are primarily metabolized by the liver but still have partial renal excretion (approx. 20-30%), making them less ideal than Atracurium in severe renal failure. * **Succinylcholine:** Generally avoided in renal failure if the patient is hyperkalemic, as it can further raise serum potassium levels by 0.5 mEq/L.

Question 480: Ketamine can be administered by all of the following routes except?

A. Intravenous (IV)
B. Intramuscular (IM)
C. Subcutaneous (SC) (Correct Answer)
D. Nasally

Explanation: **Explanation:** Ketamine is a unique phencyclidine derivative used for "dissociative anesthesia." The correct answer is **Subcutaneous (SC)** because this route is generally avoided for ketamine administration. Ketamine is highly acidic (pH 3.5 to 5.5) and can be irritating to local tissues, potentially leading to sterile abscesses or skin necrosis if injected subcutaneously. Furthermore, the absorption via this route is unpredictable compared to other systemic options. **Analysis of Options:** * **Intravenous (IV):** This is the most common route for induction. It has a rapid onset (30–60 seconds) and 100% bioavailability. * **Intramuscular (IM):** Ketamine is frequently used IM (especially in pediatrics or uncooperative patients) due to its high lipid solubility. Bioavailability is approximately 90–93%. * **Nasally:** Intranasal ketamine (and its isomer Esketamine) is increasingly used for procedural sedation and treatment-resistant depression. It is absorbed rapidly through the nasal mucosa, bypassing first-pass metabolism. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Non-competitive NMDA receptor antagonist. * **Dissociative State:** Characterized by catatonia, amnesia, and profound analgesia while the patient appears awake (eyes open, slow nystagmic gaze). * **Hemodynamics:** Unlike most anesthetics, it is a **sympathomimetic** (increases HR, BP, and CO), making it the induction agent of choice for **hypovolemic shock**. * **Airway:** It preserves airway reflexes and is a potent **bronchodilator** (drug of choice for status asthmaticus). * **Contraindications:** Raised Intracranial Pressure (ICP) and Intraocular Pressure (IOP), though these are now considered relative contraindications in modern practice. * **Side Effect:** Emergence delirium (minimized by co-administration of benzodiazepines like 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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