General Anesthesia Practice Questions

Q: Which one of the following is the shortest acting intravenous analgesic?

Remifentanil. **Explanation:** The correct answer is **Remifentanil**. The primary medical concept determining its duration of action is its unique metabolism. **Why Remifentanil is correct:** Remifentanil is an ultra-short-acting μ-opioid agonist. Unlike other opioids metabolized by the liver, Remifentanil contains an **ester linkage** that makes it susceptible to rapid hydrolysis by **nonspecific plasma and tissue esterases**. This results in an extremely short context-sensitive half-life (approximately 3–4 minutes) that remains constant regardless of the duration of infusion. This makes it ideal for procedures requiring intense analgesia with rapid recovery. **Why other options are incorrect:** * **Fentanyl:** It is a potent phenylpiperidine derivative but has a longer duration of action due to its high lipid solubility and tendency to redistribute into peripheral tissues. Its context-sensitive half-life increases significantly with prolonged infusion. * **Alfentanil:** While it has a faster onset than Fentanyl due to its low pKa (mostly unionized at physiological pH), its metabolism is hepatic (CYP3A4). It is longer-acting than Remifentanil. * **Sufentanil:** This is the most potent opioid (5–10 times more potent than Fentanyl) but has a longer elimination half-life and duration of action compared to Remifentanil. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Remifentanil metabolism is independent of renal or hepatic function (safe in organ failure). * **Context-Sensitive Half-life:** This is the time required for the plasma concentration to decrease by 50% after stopping an infusion. Remifentanil has the shortest and most stable context-sensitive half-life among all opioids. * **Potency Order:** Sufentanil > Remifentanil ≈ Fentanyl > Alfentanil > Morphine. * **Side Effect:** Rapid administration can cause significant **chest wall rigidity** (wooden chest syndrome).

Q: Which anesthetic agent is known to cause muscle rigidity?

Alfentanil. **Explanation:** **Correct Option: D. Alfentanil** The correct answer is **Alfentanil**. Muscle rigidity, specifically "Chest Wall Rigidity" (or "Wooden Chest Syndrome"), is a well-known side effect of **potent opioids**, particularly the phenylpiperidine derivatives like Fentanyl, Sufentanil, Alfentanil, and Remifentanil. * **Mechanism:** This rigidity is mediated via **mu-opioid receptors** in the central nervous system (specifically the striatum and substantia nigra). It involves a decrease in GABAergic inhibition and an increase in dopaminergic and glutamatergic outflow, leading to intense contraction of the laryngeal and skeletal muscles (especially the chest wall and abdomen), which can make bag-mask ventilation extremely difficult. **Incorrect Options:** * **A, B, and C (Halothane, Ether, Sevoflurane):** These are volatile/inhalational anesthetics. Unlike opioids, inhalational agents typically cause **muscle relaxation** (dose-dependent) and potentiate the action of neuromuscular blocking agents. While Halothane and Sevoflurane are triggers for Malignant Hyperthermia (which involves muscle rigidity), they do not cause primary muscle rigidity as a direct pharmacological effect during induction. **High-Yield Clinical Pearls for NEET-PG:** * **Management:** The drug of choice to reverse opioid-induced chest wall rigidity is a rapid-acting neuromuscular blocking agent like **Succinylcholine**. Naloxone can also reverse it but will also abolish analgesia. * **Speed of Administration:** Rigidity is most common when high doses of opioids are administered **rapidly** during induction. * **Alfentanil** has the fastest onset and shortest peak effect time among the fentanyl congeners, making it frequently associated with this phenomenon during rapid bolus administration.

Q: Suxamethonium causes all EXCEPT:

Hypokalemia. **Explanation:** **Suxamethonium (Succinylcholine)** is the only depolarizing neuromuscular blocker used clinically. It acts as an agonist at the nicotinic acetylcholine receptors, causing prolonged depolarization of the motor endplate. **Why Hypokalemia is the Correct Answer:** Suxamethonium does **not** cause hypokalemia; instead, it characteristically causes **Hyperkalemia**. During the phase of generalized muscle fasciculations, potassium is released from the intracellular compartment into the extracellular fluid. In a healthy individual, serum potassium typically rises by **0.5 mEq/L**. However, in patients with up-regulated receptors (e.g., burns, trauma, or denervation injuries), this rise can be life-threatening, leading to cardiac arrest. **Analysis of Incorrect Options:** * **A. Muscle pain:** Postoperative myalgia is a common side effect caused by the initial uncoordinated muscle fasciculations. It is most frequently seen in young adults undergoing ambulatory surgery. * **B. Malignant hyperthermia:** Suxamethonium is a potent **triggering agent** for Malignant Hyperthermia (MH) in genetically susceptible individuals (RYR1 receptor mutation). * **C. Hyperkalemia:** As explained above, the efflux of potassium during depolarization is a hallmark side effect of the drug. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For Rapid Sequence Induction (RSI) due to its rapid onset (30–60s) and short duration (5–10 mins). * **Metabolism:** Hydrolyzed by **Pseudocholinesterase** (Plasma cholinesterase). Prolonged apnea occurs in patients with atypical pseudocholinesterase (diagnosed by Dibucaine number). * **Dual Block (Phase II Block):** Occurs with repeated doses or infusion, where the block takes on characteristics of a non-depolarizing block. * **Other Side Effects:** Bradycardia (especially in children or with a second dose), increased intraocular, intragastric, and intracranial pressure.

Q: Which intravenous anesthetic agent has a high incidence of psychomimetic reactions during the early recovery period?

Ketamine. **Explanation:** **Ketamine** is the correct answer because it is a "dissociative anesthetic" that acts primarily as an NMDA receptor antagonist. The high incidence of psychomimetic reactions (10–30%) during the early recovery period is known as **Emergence Delirium**. Patients may experience vivid dreams, hallucinations, sensory distortions, and feelings of floating or detachment. These reactions occur because ketamine depresses the thalamocortical system while stimulating parts of the limbic system. **Analysis of Incorrect Options:** * **Thiopentone:** A short-acting barbiturate that primarily causes CNS depression via GABA-A receptors. Its recovery is usually smooth, though it can cause a "hangover" effect due to its high lipid solubility and redistribution. * **Propofol:** Known for its "anti-emetic" properties and rapid, clear-headed recovery. It often produces a sense of well-being or euphoria, making it the drug of choice for day-care surgery. * **Etomidate:** An imidazole derivative used for hemodynamically unstable patients. Its main side effects are pain on injection, myoclonus, and adrenocortical suppression, rather than psychomimetic reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Prevention:** Emergence delirium from Ketamine can be significantly reduced by pre-medicating the patient with **Benzodiazepines** (e.g., Midazolam). * **Contraindications:** Ketamine should be avoided in patients with schizophrenia, uncontrolled hypertension, and increased intraocular pressure. * **The "L" Effect:** Ketamine is the only IV anesthetic that is a potent **analgesic**, causes **bronchodilation**, and stimulates the **sympathetic** nervous system (increasing HR and BP).

Q: All of the following except one affect the minimum alveolar concentration (MAC)?

Altitude. **Explanation:** The **Minimum Alveolar Concentration (MAC)** is the concentration of an inhaled anesthetic at 1 atmosphere (760 mmHg) that prevents skeletal muscle movement in response to a noxious stimulus in 50% of patients. It is a measure of anesthetic **potency**. **Why Altitude is the Correct Answer:** Altitude (barometric pressure) does **not** affect the MAC of an inhalational agent. While the *partial pressure* required to achieve anesthesia remains constant, the *percentage* concentration (MAC) does not change with changes in ambient pressure. For example, if an agent has a MAC of 1% at sea level, it remains 1% at high altitude, even though the total barometric pressure is lower. **Analysis of Other Options:** * **Age (B):** MAC is highest at 6 months of age and decreases progressively with increasing age (decreases by ~6% per decade after age 20). * **Premedication (A) & Drugs (D):** Most CNS depressants decrease MAC. This includes opioids, benzodiazepines, alpha-2 agonists (clonidine, dexmedetomidine), and acute ethanol ingestion. Conversely, drugs that increase central neurotransmitters (like cocaine or amphetamines) increase MAC. **High-Yield Clinical Pearls for NEET-PG:** * **Factors Increasing MAC:** Hyperthermia, hypernatremia, chronic alcohol abuse, and red hair (MC1R gene mutation). * **Factors Decreasing MAC:** Hypothermia, hyponatremia, pregnancy (decreases by 30-40%), anemia (Hb <5g/dL), and metabolic acidosis. * **Factors with NO effect on MAC:** Duration of anesthesia, gender, thyroid status (hypo/hyper), and **altitude/barometric pressure**. * **MAC-awake:** Usually 0.3–0.5 MAC; **MAC-BAR** (Blunt Autonomic Response): Usually 1.5–2.0 MAC.

Question 1

Which one of the following is the shortest acting intravenous analgesic?

Accepted Answer

Remifentanil

Answer

Fentanyl

Answer

Alfentanil

Answer

Sufentanil

Question 2

Which anesthetic agent is known to cause muscle rigidity?

Accepted Answer

Alfentanil

Answer

Halothane

Answer

Ether

Answer

Sevoflurane

Question 3

Suxamethonium causes all EXCEPT:

Accepted Answer

Hypokalemia

Answer

Muscle pain

Answer

Malignant hyperthermia

Answer

Hyperkalemia

Question 4

Hyperkalemia is seen with succinylcholine in all of the following conditions except?

Accepted Answer

Myasthenia gravis

Answer

Tetanus

Answer

Burns

Answer

Muscular dystrophy

Question 5

What is true about Nitrous Oxide (N2O)?

Accepted Answer

It has low potency and provides good analgesia.

Answer

It is a good muscle relaxant.

Answer

It has high potency and poor analgesia.

Answer

None of the above.

Question 6

Which type of anesthesia is preferred for nasal septoplasty?

Accepted Answer

General anesthesia

Answer

Local infiltration

Answer

Propofol sedation

Answer

No anesthesia required

Question 7

Which intravenous anesthetic agent has a high incidence of psychomimetic reactions during the early recovery period?

Accepted Answer

Ketamine

Answer

Thiopentone

Answer

Propofol

Answer

Etomidate

Question 8

Propofol causes pain on injection. Which of the following statements is incorrect?

Accepted Answer

It is due to the 1-2% egg lecithin component, causing crystallization in the veins.

Answer

It is kallikrein pathway mediated.

Answer

It can be reduced by adding 1% lignocaine to the syringe.

Answer

Use of larger veins decreases the incidence.

Question 9

The action of intravenous thiopentone is terminated by which mechanism?

Accepted Answer

Redistribution

Answer

Rapid renal excretion

Answer

Oxidation

Answer

Conjugation

Question 10

All of the following except one affect the minimum alveolar concentration (MAC)?

Accepted Answer

Altitude

Answer

Premedication

Answer

Age

Answer

Drugs

General Anesthesia — MCQs

General Anesthesia — MCQs

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