General Anesthesia — MCQs
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A 32-year-old female presents with pain in the right lower iliac fossa and positive rebound tenderness. She underwent appendectomy under general anesthesia. Postoperative laboratory findings showed increased levels of transaminases with the absence of increased bilirubin. Which of the following anesthetic agents is most likely responsible for the elevation of the enzymes?
Which of the following statements regarding pancuronium is INCORRECT?
Which of the following agents possesses antiemetic action?
Which of the following statements about sevoflurane is true?
Which of the following is NOT an aminosteroid non-depolarizing neuromuscular blocker?
Laudanosine is a metabolite of which neuromuscular blocking agent?
Inhaled general anesthetics with a low blood-gas partition coefficient are characterized by what?
Etomidate causes all of the following except:
Which of the following drugs produces a subjective feeling of well-being on emergence, thus conferring a potential for substance abuse?
What percentage of Halothane is metabolized?
General Anesthesia Indian Medical PG Practice Questions and MCQs
Question 161: A 32-year-old female presents with pain in the right lower iliac fossa and positive rebound tenderness. She underwent appendectomy under general anesthesia. Postoperative laboratory findings showed increased levels of transaminases with the absence of increased bilirubin. Which of the following anesthetic agents is most likely responsible for the elevation of the enzymes?
- A. Nitrous oxide
- B. Halothane (Correct Answer)
- C. Methoxyflurane
- D. Enflurane
Explanation: **Explanation:** The clinical presentation describes a classic case of **Halothane-induced Hepatotoxicity**. Halothane is a volatile anesthetic agent known to cause two types of liver injury. The scenario describes **Type I (Minor) Hepatotoxicity**, which is characterized by a transient, asymptomatic rise in serum transaminases (ALT/AST) without a significant increase in bilirubin. **Why Halothane is the correct answer:** Halothane undergoes significant hepatic metabolism (up to 20%) via the Cytochrome P450 system. This process produces reactive intermediates (trifluoroacetylated proteins) that can cause direct hepatocellular damage or trigger an immune-mediated response (Type II/Major Hepatotoxicity, which involves jaundice and high mortality). Risk factors include female gender, obesity, and multiple exposures. **Analysis of Incorrect Options:** * **Nitrous oxide (A):** It is not metabolized by the liver and is not associated with hepatotoxicity. Its primary concerns are megaloblastic anemia (B12 inhibition) and expansion of closed gas spaces. * **Methoxyflurane (C):** While it is highly metabolized, its primary toxicity is **nephrotoxicity** (due to inorganic fluoride ions), leading to high-output renal failure. * **Enflurane (D):** It is metabolized much less than halothane (approx. 2%). While it carries a theoretical risk of hepatotoxicity, it is significantly lower than halothane. Its most characteristic side effect is lowering the seizure threshold (epileptogenic). **Clinical Pearls for NEET-PG:** * **Metabolism Rule:** Halothane (20%) > Enflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). Higher metabolism correlates with higher hepatotoxic potential. * **Halothane Hepatitis:** More common in adults than children; "Halothane shakes" (postoperative shivering) is another common side effect. * **Sevoflurane:** Associated with **Compound A** formation in soda lime, which is nephrotoxic in rats (though clinical significance in humans is debated).
Question 162: Which of the following statements regarding pancuronium is INCORRECT?
- A. It is an aminosteroid skeletal muscle relaxant.
- B. It is a vagal stimulant. (Correct Answer)
- C. Cardiovascular side effects are common.
- D. It is the second-longest acting neuromuscular blocker after doxacurium.
Explanation: ### Explanation **Pancuronium** is a long-acting, non-depolarizing neuromuscular blocking agent (NMBA). Understanding its pharmacological profile is essential for NEET-PG, particularly its cardiovascular effects. **1. Why Option B is Incorrect (The Correct Answer):** Pancuronium is **not a vagal stimulant**; rather, it is a **vagolytic**. It acts as a competitive antagonist at the muscarinic (M2) receptors in the heart. By blocking the inhibitory effects of the vagus nerve, it leads to an increase in heart rate (tachycardia) and a slight increase in blood pressure. This "vagolytic effect" is its most characteristic side effect. **2. Analysis of Other Options:** * **Option A:** Pancuronium belongs to the **aminosteroid** class of NMBAs (along with vecuronium and rocuronium). Unlike benzylisoquinolines (e.g., atracurium), aminosteroids do not typically cause histamine release. * **Option C:** Cardiovascular side effects are indeed **common**. Due to its vagolytic action and sympathetic stimulation (inhibition of norepinephrine reuptake), tachycardia and hypertension are frequently observed, making it less ideal for patients with coronary artery disease. * **Option D:** It is classified as a **long-acting** agent. While doxacurium and pipecuronium are the longest-acting, pancuronium is traditionally considered the second-longest acting agent still in clinical discussion, with a duration of action exceeding 60–90 minutes. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Primarily renal (80% excreted unchanged). It should be avoided in patients with **renal failure** due to the risk of prolonged paralysis. * **Active Metabolite:** 3-OH pancuronium (has about 50% of the potency of the parent drug). * **Key Association:** If a question mentions a muscle relaxant causing **tachycardia**, think Pancuronium or Gallamine. * **Reversal:** Like other non-depolarizing agents, it is reversed with Neostigmine (acetylcholinesterase inhibitor) or Sugammadex (though Sugammadex is more commonly used for Rocuronium/Vecuronium).
Question 163: Which of the following agents possesses antiemetic action?
- A. Propofol (Correct Answer)
- B. Thiopentone
- C. Ether
- D. Nitrous oxide
Explanation: **Explanation:** **Propofol (Option A)** is the correct answer because it is the only intravenous anesthetic agent with significant **intrinsic antiemetic properties**. Its mechanism involves the modulation of subcortical pathways, inhibition of the chemoreceptor trigger zone (CTZ), and reduction of dopamine levels in the area postrema. Even at sub-hypnotic doses (10–20 mg), propofol is highly effective in treating and preventing Postoperative Nausea and Vomiting (PONV). It is the agent of choice for Total Intravenous Anesthesia (TIVA) in patients at high risk for PONV. **Why the other options are incorrect:** * **Thiopentone (Option B):** A barbiturate that is considered "emetic neutral." It does not possess antiemetic properties and, unlike propofol, does not reduce the incidence of PONV. * **Ether (Option C):** Historically notorious for causing a very high incidence of severe postoperative nausea and vomiting due to gastric irritation and sympathetic stimulation. * **Nitrous Oxide (Option D):** A known **emetogenic agent**. It increases PONV by increasing middle ear pressure, causing bowel distension, and stimulating the CTZ. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol** is also known as the "Milk of Amnesia" due to its soybean oil/egg lecithin emulsion. * **Drug of choice** for day-care surgery because of its rapid recovery and antiemetic profile. * **Contraindication:** Avoid in patients with a history of egg allergy (specifically egg yolk) or disorders of lipid metabolism. * **Other antiemetic anesthetics:** Midazolam also possesses mild antiemetic properties, but Propofol is the most potent.
Question 164: Which of the following statements about sevoflurane is true?
- A. It is nephrotoxic at high doses. (Correct Answer)
- B. It has the maximum risk of causing convulsions.
- C. It is cardiostable.
- D. It can cause fulminant hepatitis.
Explanation: **Explanation:** **1. Why Option A is Correct:** Sevoflurane undergoes degradation by **soda lime** (carbon dioxide absorbents) in the anesthesia circuit to produce a vinyl ether called **Compound A**. In laboratory animals, Compound A has been shown to be **nephrotoxic**. While its clinical significance in humans is debated, current guidelines recommend using a fresh gas flow of at least 1–2 L/min to prevent the accumulation of Compound A, especially during prolonged surgeries. **2. Why Other Options are Incorrect:** * **Option B:** The anesthetic agent with the maximum risk of causing convulsions (seizure-like EEG activity) is **Enflurane**. While Sevoflurane can occasionally show epileptiform patterns on EEG in pediatric inductions, Enflurane is the classic association for NEET-PG. * **Option C:** Sevoflurane is not strictly "cardiostable." It causes dose-dependent peripheral vasodilation and can decrease blood pressure. The most cardiostable inhalational agent is **Etomidate** (among IV agents) or **Isoflurane/Desflurane** (relative to Halothane). However, Sevoflurane is preferred for induction because it does not cause tachycardia. * **Option D:** Fulminant hepatitis (Halothane Hepatitis) is classically associated with **Halothane** due to the formation of trifluoroacetylated liver proteins. Sevoflurane does not undergo metabolism to these reactive intermediates. **High-Yield Clinical Pearls for NEET-PG:** * **Sweet Smell:** Sevoflurane is non-pungent and pleasant-smelling, making it the **agent of choice for inhalation induction** in children. * **Low Solubility:** It has a low blood-gas partition coefficient (0.42), leading to rapid induction and recovery. * **Boiling Point:** It has a high boiling point (58.5°C), allowing it to be used in conventional vaporizers (unlike Desflurane). * **Metabolism:** It is metabolized to inorganic fluoride, but unlike Methoxyflurane, it rarely reaches levels high enough to cause fluoride-induced nephrotoxicity.
Question 165: Which of the following is NOT an aminosteroid non-depolarizing neuromuscular blocker?
- A. Pancuronium
- B. Pipecuronium
- C. Gantacurium (Correct Answer)
- D. Vacuronium
Explanation: **Explanation:** Neuromuscular blocking agents (NMBAs) are broadly classified into two chemical classes: **Aminosteroids** and **Benzylisoquinolines**. **Why Gantacurium is the correct answer:** Gantacurium belongs to the **Benzylisoquinoline** class (specifically a chlorofumarate derivative). It is a newer, ultra-short-acting non-depolarizing agent designed to be degraded by non-enzymatic cysteine adduction and ester hydrolysis. Unlike aminosteroids, benzylisoquinolines are generally associated with histamine release but do not have the steroid nucleus. **Analysis of incorrect options:** * **Pancuronium:** A long-acting **aminosteroid**. It is known for its vagolytic effect, which can cause tachycardia. * **Pipecuronium:** A long-acting **aminosteroid** similar to pancuronium but without the significant cardiovascular side effects (vagolytic activity). * **Vecuronium:** An intermediate-acting **aminosteroid**. It is the mono-quaternary analog of pancuronium, lacks vagolytic effects, and is primarily excreted via bile. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Aminosteroids:** Remember the suffix **"-curonium"** (Pancuronium, Vecuronium, Rocuronium, Pipecuronium). * **Mnemonic for Benzylisoquinolines:** Remember the suffix **"-curium"** (Atracurium, Cisatracurium, Mivacurium, Gantacurium). * **Rocuronium** is the aminosteroid with the fastest onset, making it an alternative for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated. * **Sugammadex** is a specific reversal agent that works only for aminosteroids (Rocuronium > Vecuronium > Pancuronium) by encapsulation; it has no effect on Gantacurium or other benzylisoquinolines.
Question 166: Laudanosine is a metabolite of which neuromuscular blocking agent?
- A. Cisatracurium
- B. Atracurium (Correct Answer)
- C. Pancuronium
- D. Gallamine
Explanation: **Explanation:** **Atracurium** is the correct answer because it undergoes a unique spontaneous degradation process known as **Hofmann elimination** (a non-enzymatic, pH and temperature-dependent pathway) and ester hydrolysis. The primary metabolic byproduct of these processes is **Laudanosine**, a tertiary amine. * **Why Atracurium is correct:** Laudanosine is the major metabolite of both Atracurium and its isomer, Cisatracurium. However, Atracurium produces significantly higher levels of Laudanosine (approximately 3–5 times more) compared to Cisatracurium. * **Why other options are incorrect:** * **Cisatracurium:** While it also produces Laudanosine, Atracurium is the classic association in exams due to the higher volume produced. In a single-choice question, Atracurium is the primary answer. * **Pancuronium:** This is a long-acting aminosteroid NMBA primarily excreted unchanged by the kidneys (80%). It does not produce Laudanosine. * **Gallamine:** This is an older, long-acting agent excreted entirely unchanged by the kidneys. It is now largely obsolete in clinical practice. **Clinical Pearls for NEET-PG:** 1. **CNS Toxicity:** Laudanosine is a **CNS stimulant**. In high concentrations (rare in routine clinical use but possible in prolonged ICU infusions), it can cross the blood-brain barrier and potentially cause **seizures**. 2. **Organ Independence:** Because Atracurium relies on Hofmann elimination, it is the drug of choice (along with Cisatracurium) for patients with **renal or hepatic failure**. 3. **Histamine Release:** Unlike Cisatracurium, Atracurium is associated with dose-dependent histamine release, which can cause flushing, hypotension, and bronchospasm.
Question 167: Inhaled general anesthetics with a low blood-gas partition coefficient are characterized by what?
- A. Rapid induction and quick recovery from anesthesia (Correct Answer)
- B. Rapid induction and slow recovery from anesthesia
- C. Slow induction and slow recovery from anesthesia
- D. Slow induction and quick recovery from anesthesia
Explanation: ### Explanation The speed of induction and recovery of an inhaled anesthetic is primarily determined by its **Blood-Gas Partition Coefficient (λ)**, which represents the drug's solubility in blood. **1. Why Option A is Correct:** The Blood-Gas Partition Coefficient indicates how much of the anesthetic dissolves in the blood compared to the alveolar gas. * **Low Solubility (Low λ):** Agents like **Desflurane (0.42)** or **Sevoflurane (0.65)** are relatively insoluble in blood. Because the blood "fills up" quickly, the partial pressure of the gas in the alveoli rises rapidly, leading to a faster equilibrium with the brain. * **Rapid Induction:** A faster rise in alveolar partial pressure ($F_A/F_I$ ratio) translates to a faster onset of anesthesia. * **Quick Recovery:** When the anesthetic is stopped, the blood quickly clears the drug back into the lungs for exhalation, leading to rapid emergence. **2. Why Other Options are Incorrect:** * **Options B, C, & D:** These are physiologically inconsistent. Induction and recovery speeds are generally symmetrical. A drug that is slow to enter the blood (high solubility) will also be slow to leave it. High blood-gas partition coefficients (e.g., **Halothane, λ = 2.4**) act as a large reservoir, "soaking up" the gas and delaying the rise in partial pressure, resulting in **slow induction and slow recovery**. **3. NEET-PG High-Yield Pearls:** * **Inverse Relationship:** Solubility is inversely proportional to the speed of induction. * **Order of Solubility (Lowest to Highest):** Desflurane < Nitrous Oxide < Sevoflurane < Isoflurane < Halothane. * **The Concentration Effect:** Nitrous oxide (though slightly more soluble than Desflurane) has a very rapid induction because it is delivered in high concentrations (70%), unlike potent vapors used in low concentrations. * **Oil-Gas Partition Coefficient:** This determines the **Potency** (MAC) of the drug, not the speed of induction. High oil-gas solubility = High potency = Low MAC.
Question 168: Etomidate causes all of the following except:
- A. Coronary insufficiency (Correct Answer)
- B. Decreased steroidogenesis
- C. Decreased intracranial tension
- D. Nausea and vomiting
Explanation: **Explanation:** **Etomidate** is a carboxylated imidazole derivative used for the induction of general anesthesia. It is famously known for its **hemodynamic stability**, making it the induction agent of choice for patients with cardiovascular disease or shock. **Why Option A is the Correct Answer:** Etomidate **does not cause coronary insufficiency**. In fact, it maintains stable systemic blood pressure, heart rate, and myocardial oxygen delivery. It has minimal effect on sympathetic tone and does not cause histamine release, ensuring that coronary perfusion pressure is well-maintained. **Analysis of Incorrect Options:** * **B. Decreased steroidogenesis:** This is the most characteristic side effect of Etomidate. It causes dose-dependent inhibition of the enzyme **11-beta-hydroxylase**, which is essential for cortisol and aldosterone synthesis. This can lead to adrenocortical suppression even after a single dose. * **C. Decreased intracranial tension (ICT):** Etomidate is a potent cerebral vasoconstrictor. It reduces cerebral blood flow (CBF) and the cerebral metabolic rate of oxygen (CMRO2), which subsequently leads to a decrease in ICT. * **D. Nausea and vomiting:** Postoperative nausea and vomiting (PONV) is significantly more common with Etomidate compared to other induction agents like propofol. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For induction in patients with **valvular heart disease, coronary artery disease, or hypovolemia**. * **Myoclonus:** Etomidate frequently causes involuntary muscle movements (myoclonus) during induction, which can be attenuated by pre-medication with opioids or benzodiazepines. * **Solvent:** It is traditionally formulated in **propylene glycol**, which can cause pain on injection. * **Contraindication:** Relative contraindication in patients with **sepsis** due to its effect on the adrenal axis.
Question 169: Which of the following drugs produces a subjective feeling of well-being on emergence, thus conferring a potential for substance abuse?
- A. Thiopentone
- B. Propofol (Correct Answer)
- C. Etomidate
- D. Ketamine
Explanation: **Explanation:** The correct answer is **Propofol (Option B)**. Propofol is a short-acting intravenous anesthetic agent that acts primarily via the GABA-A receptor. It is unique among induction agents for producing a **subjective feeling of well-being, euphoria, and clear-headedness** during the emergence phase. This "pleasant" recovery is attributed to the release of dopamine in the nucleus accumbens (the brain's reward center). Consequently, Propofol has a documented potential for **substance abuse**, particularly among healthcare professionals with easy access to the drug. **Analysis of Incorrect Options:** * **A. Thiopentone:** A barbiturate that often causes a "hangover" effect or grogginess upon emergence. It does not typically produce euphoria. * **C. Etomidate:** Known for its cardiovascular stability, but it is associated with a high incidence of postoperative nausea and vomiting (PONV) and myoclonus, making the recovery period less pleasant. * **D. Ketamine:** Produces "dissociative anesthesia." While it can cause hallucinations, the emergence period is often characterized by **emergence delirium**, agitation, and vivid unpleasant dreams rather than a simple feeling of well-being. **High-Yield NEET-PG Pearls:** * **Propofol** is the drug of choice for Day Care (Ambulatory) Surgery due to its rapid metabolism and anti-emetic properties. * **Propofol Infusion Syndrome (PRIS):** A rare but fatal complication characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure (seen with high doses/long duration). * **Pain on injection** is a common side effect of Propofol (minimized by using larger veins or pre-treatment with Lidocaine). * **Egg/Soy Allergy:** Use caution, as Propofol is formulated in a lipid emulsion containing soybean oil and egg lecithin.
Question 170: What percentage of Halothane is metabolized?
- A. 50%
- B. 5%
- C. 2.50%
- D. 25% (Correct Answer)
Explanation: **Explanation:** The metabolism of volatile anesthetic agents occurs primarily in the liver via the **Cytochrome P450 (CYP2E1)** enzyme system. Among the potent inhalational agents, **Halothane** undergoes the most extensive hepatic metabolism. **1. Why 25% is Correct:** Approximately **20% to 25%** of Halothane is metabolized in the liver. This high rate of metabolism is clinically significant because it leads to the production of reactive intermediates (like trifluoroacetylated proteins). These metabolites can trigger an immune-mediated response, leading to **Halothane Hepatitis**, a rare but severe form of liver injury. **2. Analysis of Incorrect Options:** * **A (50%):** No commonly used volatile anesthetic reaches this level of metabolism. * **B (5%):** This is the approximate metabolism rate for **Sevoflurane** (2%–5%). * **C (2.50%):** This does not correspond to a specific major agent; however, **Enflurane** is metabolized at a rate of about 2%. * **D (25%):** This is the established high-yield value for Halothane. **3. High-Yield NEET-PG Clinical Pearls:** * **Metabolism Ranking (Highest to Lowest):** Halothane (25%) > Sevoflurane (2-5%) > Enflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Halothane Hepatitis:** More common in adults, females, and obese patients upon repeat exposure. * **Metabolite:** The oxidative metabolism of Halothane produces **trifluoroacetic acid**. * **Rule of Thumb:** Desflurane is the least metabolized (most stable), while Halothane is the most metabolized (least stable).
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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