General Anesthesia Practice Questions

Q: Which of the following is a known effect of suxamethonium?

Muscle fasciculation. **Explanation:** **Suxamethonium (Succinylcholine)** is the only depolarizing neuromuscular blocking agent used clinically. It acts as an agonist at the nicotinic acetylcholine receptors (nAChR) at the neuromuscular junction. **Why Option D is Correct:** Unlike non-depolarizing agents, suxamethonium causes prolonged depolarization of the post-synaptic membrane. This initial stimulation leads to disorganized contractions of muscle units known as **muscle fasciculations** before the onset of flaccid paralysis. These fasciculations are often associated with postoperative myalgia. **Why Other Options are Incorrect:** * **A & B (Jaundice & Splenomegaly):** Suxamethonium has no known hepatotoxic effects or impact on splenic volume. Jaundice is more classically associated with repeated exposure to Halothane (Halothane hepatitis). * **C (Atrial Fibrillation):** While suxamethonium can cause arrhythmias, its most characteristic cardiac effect is **bradycardia** (especially in children or upon a second dose) due to its action on muscarinic receptors in the sinus node. It may also cause ventricular arrhythmias secondary to hyperkalemia, but not typically atrial fibrillation. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Hydrolyzed by **pseudocholinesterase** (butyrylcholinesterase). Deficiency leads to prolonged apnea (Suxamethonium apnea). * **Electrolyte Shift:** Causes a transient **increase in serum potassium** (approx. 0.5 mEq/L); contraindicated in burns, crush injuries, and upper motor neuron lesions due to risk of fatal hyperkalemia. * **Pressure Changes:** Increases intraocular, intragastric, and intracranial pressure. * **Malignant Hyperthermia:** It is a potent trigger for Malignant Hyperthermia (Treatment: Dantrolene).

Q: A 21-year-old woman with a history of hypersensitivity to neostigmine is scheduled for an elective cesarean section under general anesthesia. Which muscle relaxant is the best choice for this patient?

Atracurium. **Explanation:** The core clinical challenge in this scenario is the patient’s **hypersensitivity to neostigmine**. Neostigmine is the standard pharmacological reversal agent for non-depolarizing neuromuscular blocking agents (NDMRs). If a patient cannot receive neostigmine, the anesthesiologist must select a muscle relaxant that does not strictly depend on pharmacological reversal for the termination of its effects. **Why Atracurium is the Correct Choice:** Atracurium (and its isomer Cisatracurium) undergoes **Hofmann elimination**—a spontaneous, non-enzymatic degradation at physiological pH and temperature. Because it is self-terminating and does not rely on hepatic metabolism or renal excretion, the block wears off predictably on its own. In a patient where neostigmine is contraindicated, choosing a drug with a reliable "spontaneous recovery" profile is the safest strategy. **Analysis of Incorrect Options:** * **Pancuronium (A):** A long-acting NDMR primarily excreted by the kidneys. It requires mandatory reversal to avoid residual paralysis, making it unsuitable here. * **Rocuronium (C) & Vecuronium (D):** These are intermediate-acting aminosteroid compounds. While Rocuronium can be reversed with Sugammadex (a non-anticholinesterase agent), in the context of standard NEET-PG questions, Atracurium remains the classic answer for "avoiding neostigmine" due to its unique organ-independent elimination. **High-Yield Clinical Pearls for NEET-PG:** * **Hofmann Elimination:** Dependent on **pH and Temperature**. Rate increases with alkalosis/hyperthermia and decreases with acidosis/hypothermia. * **Laudanosine:** A metabolite of atracurium that can cross the blood-brain barrier and potentially cause seizures (though rare in clinical doses). * **Drug of Choice:** Atracurium/Cisatracurium are the drugs of choice in **Renal and Hepatic failure**.

Q: Which volatile anesthetic agent causes the most renal toxicity?

Methoxyflurane. **Explanation:** The correct answer is **Methoxyflurane**. The primary mechanism behind its renal toxicity is the extensive hepatic metabolism of the drug, which releases **inorganic fluoride ions ($F^-$)**. 1. **Why Methoxyflurane is correct:** Methoxyflurane undergoes the highest degree of metabolism (approx. 50–75%) among all volatile agents. This results in high serum fluoride levels (often exceeding 50 µmol/L). These fluoride ions cause **vasopressin-resistant high-output renal failure** (polyuric renal failure) by damaging the distal convoluted tubules and collecting ducts, making them unresponsive to ADH. Due to this severe nephrotoxicity, it is no longer used for general anesthesia. 2. **Why other options are incorrect:** * **Ether:** Primarily known for its irritant effect on airways and flammability; it does not produce toxic fluoride metabolites. * **Isoflurane:** It is very stable and undergoes minimal metabolism (0.2%), making it exceptionally safe for the kidneys. * **Sevoflurane:** While it does release fluoride ions and can produce **Compound A** (a nephrotoxin in rats) when reacting with soda lime, clinical studies have shown no significant evidence of renal toxicity in humans when used at recommended flow rates. **High-Yield Clinical Pearls for NEET-PG:** * **Fluoride-induced nephrotoxicity:** Characterized by polyuria, hypernatremia, and increased serum creatinine. * **Metabolism Ranking (Highest to Lowest):** Methoxyflurane (50-75%) > Halothane (20%) > Sevoflurane (2-5%) > Enflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Compound A:** Associated with **Sevoflurane**; formed by degradation in carbon dioxide absorbers (especially with low-flow anesthesia). * **Agent of choice in Renal Failure:** Isoflurane or Desflurane.

Q: A 60-year-old man undergoing an inguinal hernia repair is induced with propofol. Which of the following is most likely to be observed?

Apnea. **Explanation:** Propofol (2,6-diisopropylphenol) is the most commonly used intravenous induction agent. Its primary mechanism of action involves the enhancement of GABA-A receptors in the central nervous system. **Why Apnea is the Correct Answer:** Propofol is a potent respiratory depressant. Following an induction dose (1.5–2.5 mg/kg), it frequently causes **transient apnea** (lasting >30 seconds) by decreasing the sensitivity of the medullary respiratory center to carbon dioxide and reducing the tidal volume and respiratory rate. This effect is more pronounced than with other induction agents like thiopentone. **Analysis of Incorrect Options:** * **A. Hypertension:** Propofol typically causes **hypotension**, not hypertension. It reduces systemic vascular resistance (vasodilation) and myocardial contractility, making it the most hemodynamically unstable induction agent among common choices. * **C. Hyperthermia:** Propofol does not cause hyperthermia. In fact, it is the drug of choice for patients susceptible to **Malignant Hyperthermia**, as it is a non-triggering agent. * **D. Prolonged sedation:** Propofol is characterized by a **rapid recovery** profile. Due to its high lipid solubility and rapid redistribution from the brain to peripheral tissues, patients wake up quickly (usually within 5–10 minutes) with minimal "hangover" effect. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For day-care (ambulatory) surgeries due to rapid recovery and anti-emetic properties. * **Pain on Injection:** A common side effect; minimized by using larger veins or pre-treatment with lidocaine. * **PRIS (Propofol Infusion Syndrome):** A rare, fatal complication of long-term high-dose infusion characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure. * **Egg/Soy Allergy:** Use with caution as the emulsion contains egg lecithin and soybean oil.

Q: An anesthetic tension in the arterial blood is shown on the graph as a function of time after inhalation. A similar curve for nitrous oxide is also shown. Which of the following best describes the properties of the new anesthetic compared to nitrous oxide?

High blood:gas partition coefficient. ***High blood:gas partition coefficient*** - The slower rise in **FA/FI ratio** (alveolar to inspired concentration) indicates the anesthetic has **high blood solubility**, meaning more drug dissolves in blood before reaching equilibrium. - A **high blood:gas partition coefficient** means the anesthetic is readily taken up by blood, delaying the rise in alveolar concentration compared to nitrous oxide. *Low solubility in the blood* - This would result in a **rapid rise** in FA/FI ratio, similar to or faster than nitrous oxide, which is not shown in the graph. - **Low blood solubility** means less drug dissolves in blood, allowing faster equilibration between alveolar and inspired concentrations. *Rapid onset of action* - The graph shows a **slower equilibration** compared to nitrous oxide, indicating **delayed onset** rather than rapid onset. - **Rapid onset** would be associated with a steep, quick rise in FA/FI ratio, which contradicts the shown curve. *Low potency* - **Potency** is determined by **MAC (Minimum Alveolar Concentration)**, not by the equilibration curve shown in the graph. - The blood:gas partition coefficient and equilibration speed are **independent of potency**, which relates to receptor binding affinity.

Q: Which of the following muscle relaxants is free of cardiovascular effects over the entire clinical dose range?

Vecuronium. **Explanation:** The cardiovascular stability of neuromuscular blocking agents (NMBAs) depends on their ability to trigger histamine release or interact with autonomic receptors (muscarinic or nicotinic). **Why Vecuronium is Correct:** Vecuronium is a monoquaternary aminosteroid NMBA known for its **cardiovascular stability**. It does not cause histamine release and has negligible effects on autonomic ganglia or muscarinic receptors. Consequently, it does not cause changes in heart rate or blood pressure, even at doses several times the $ED_{95}$, making it the drug of choice for patients where hemodynamic stability is critical. **Analysis of Incorrect Options:** * **Pancuronium:** This is a long-acting aminosteroid that causes **tachycardia** and hypertension. This is due to its vagolytic effect (blocking $M_2$ receptors in the heart) and its ability to stimulate norepinephrine release from sympathetic nerve endings. * **Atracurium:** This benzylisoquinolone is associated with **histamine release**, especially when administered rapidly or at high doses. This can lead to systemic vasodilation (hypotension) and reflex tachycardia. * **Pipecuronium:** While it is more stable than pancuronium, it can still exhibit mild cardiovascular effects at very high doses, though it is much closer to vecuronium in stability. However, vecuronium remains the classic textbook answer for "free of effects over the entire clinical range." **High-Yield NEET-PG Pearls:** * **Rocuronium:** Also cardiovascularly stable but may cause a slight increase in heart rate. * **Cisatracurium:** The most stable benzylisoquinolone (no histamine release), often used in renal/hepatic failure (Hofmann elimination). * **Mivacurium:** Shortest acting non-depolarizer; significant histamine release. * **Succinylcholine:** Can cause **bradycardia** (especially in children or on second dose) due to muscarinic stimulation.

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

Halothane is a good analgesic agent.. **Explanation:** Halothane is a potent inhalational anesthetic agent, but it is characterized by a significant clinical limitation: it is a **potent hypnotic but a poor analgesic**. In clinical practice, this means that while halothane can induce unconsciousness, it does not effectively block pain signals. Therefore, it must be supplemented with other analgesic agents (like opioids or nitrous oxide) to ensure a pain-free surgical state. **Analysis of Options:** * **Option A (Correct):** Halothane provides minimal analgesia. This makes the statement "Halothane is a good analgesic" false. * **Option B:** Halothane sensitizes the myocardium to the effects of circulating catecholamines (epinephrine/norepinephrine). This increases the risk of ventricular arrhythmias, especially if exogenous adrenaline is used during surgery. * **Option C:** Halothane is a potent bronchodilator. It is non-irritating to the airways and inhibits bronchial secretions, making it a historically preferred agent for patients with asthma or COPD. * **Option D:** "Halothane Hepatitis" is a well-known complication. It occurs due to the metabolism of halothane into trifluoroacetylated proteins, which can trigger an immune-mediated hepatotoxicity and centrilobular necrosis. **High-Yield Clinical Pearls for NEET-PG:** * **MAC of Halothane:** 0.75% (highly potent). * **Metabolism:** Approximately 20% is metabolized in the liver (highest among common inhalational agents). * **Uterine Effect:** It causes significant uterine relaxation, which can lead to postpartum hemorrhage (PPH) if used in obstetrics. * **Malignant Hyperthermia:** Like all volatile anesthetics, halothane is a known trigger.

Q: Which muscle relaxant can be used in a patient with high serum bilirubin of 6.0 mg/dL and serum creatinine of 4.5 mg/dL?

Atracurium. **Explanation:** The correct answer is **Atracurium**. The clinical scenario describes a patient with both hepatic impairment (Bilirubin 6.0 mg/dL) and renal failure (Creatinine 4.5 mg/dL). In such cases, the ideal muscle relaxant is one that does not rely on the liver or kidneys for metabolism or excretion. **Why Atracurium is correct:** Atracurium (and its isomer Cisatracurium) undergoes **Hofmann Elimination**—a unique organ-independent chemical degradation that occurs at physiological pH and temperature. It also undergoes ester hydrolysis by non-specific plasma esterases. Because it does not depend on hepatic or renal function, its duration of action remains predictable even in multi-organ failure. **Why other options are incorrect:** * **Vecuronium:** Primarily undergoes hepatic metabolism and biliary excretion (approx. 40-70%). Its duration is significantly prolonged in patients with liver disease. * **Pancuronium:** Primarily excreted by the kidneys (approx. 80%). It would lead to profound neuromuscular blockade and "recurarization" in a patient with a creatinine of 4.5 mg/dL. * **Mivacurium:** While metabolized by plasma cholinesterase, its clearance is significantly delayed in both liver and renal failure due to decreased enzyme production and altered distribution volumes. **NEET-PG High-Yield Pearls:** * **Hofmann Elimination:** Is a temperature and pH-dependent process. Acidosis and hypothermia *slow down* the elimination, prolonging the drug's effect. * **Laudanosine:** A major metabolite of atracurium. It is a CNS stimulant that can lower the seizure threshold (though rarely clinical at standard doses). * **Drug of Choice:** Cisatracurium is often preferred over Atracurium in clinical practice because it produces less histamine release and less laudanosine. * **Renal Failure:** Avoid Gallamine (100% renal excretion) and Pancuronium.

Question 1

Which of the following is a known effect of suxamethonium?

Accepted Answer

Muscle fasciculation

Answer

Jaundice

Answer

Splenomegaly

Answer

Atrial fibrillation

Question 2

A 21-year-old woman with a history of hypersensitivity to neostigmine is scheduled for an elective cesarean section under general anesthesia. Which muscle relaxant is the best choice for this patient?

Accepted Answer

Atracurium

Answer

Pancuronium

Answer

Rocuronium

Answer

Vecuronium

Question 3

Nitrous oxide is contraindicated in which of the following conditions?

Accepted Answer

Mastectomy

Answer

Vitreo-retinal surgeries

Answer

Pneumothorax

Answer

Laser surgery

Question 4

Pain during injection occurs with all anesthetic agents listed below except?

Accepted Answer

Ketamine

Answer

Propofol

Answer

Thiopentone

Answer

Etomidate

Question 5

Which volatile anesthetic agent causes the most renal toxicity?

Accepted Answer

Methoxyflurane

Answer

Ether

Answer

Isoflurane

Answer

Sevoflurane

Question 6

A 60-year-old man undergoing an inguinal hernia repair is induced with propofol. Which of the following is most likely to be observed?

Accepted Answer

Apnea

Answer

Hypertension

Answer

Hyperthermia

Answer

Prolonged sedation

Question 7

An anesthetic tension in the arterial blood is shown on the graph as a function of time after inhalation. A similar curve for nitrous oxide is also shown. Which of the following best describes the properties of the new anesthetic compared to nitrous oxide?

Accepted Answer

High blood:gas partition coefficient

Answer

Low solubility in the blood

Answer

Rapid onset of action

Answer

Low potency

Question 8

Which of the following muscle relaxants is free of cardiovascular effects over the entire clinical dose range?

Accepted Answer

Vecuronium

Answer

Pancuronium

Answer

Atracurium

Answer

Pipecuronium

Question 9

Which of the following statements about Halothane is FALSE?

Accepted Answer

Halothane is a good analgesic agent.

Answer

Halothane sensitizes the heart to catecholamines.

Answer

Halothane relaxes the bronchi.

Answer

Halothane causes hepatitis and liver cell necrosis.

Question 10

Which muscle relaxant can be used in a patient with high serum bilirubin of 6.0 mg/dL and serum creatinine of 4.5 mg/dL?

Accepted Answer

Atracurium

Answer

Vecuronium

Answer

Pancuronium

Answer

Mivacurium

General Anesthesia — MCQs

General Anesthesia — MCQs

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