General Anesthesia Practice Questions

Q: Which of the following drugs inhibits the enzyme 11-beta-hydroxylase responsible for cortisol synthesis?

Etomidate. ### Explanation **Correct Answer: C. Etomidate** **Mechanism of Action:** Etomidate is a carboxylated imidazole derivative used for the induction of general anesthesia. Its most characteristic side effect is the **dose-dependent inhibition of the enzyme 11-beta-hydroxylase**. This enzyme is essential for converting 11-deoxycortisol to cortisol and 11-deoxycorticosterone to aldosterone in the adrenal cortex. Even a single induction dose can suppress adrenocortical function for 6–24 hours, making it potentially hazardous for patients with sepsis or those requiring a sustained stress response. **Analysis of Incorrect Options:** * **A. Thiopentone:** A barbiturate that acts by increasing the duration of GABA-A receptor opening. It does not interfere with steroidogenesis but is known for causing histamine release and dose-dependent cardiovascular depression. * **B. Propofol:** An isopropylphenol that enhances GABAergic transmission. While it causes significant hypotension (vasodilation), it has no inhibitory effect on adrenal enzymes. * **C. Ketamine:** A phencyclidine derivative that acts as an NMDA receptor antagonist. It is unique for its sympathomimetic effects (increasing BP and HR) and does not inhibit cortisol synthesis. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Etomidate is the induction agent of choice for **hemodynamically unstable patients** (e.g., shock, severe cardiovascular disease) because it has minimal effects on heart rate and blood pressure. * **Myoclonus:** Etomidate is frequently associated with excitatory movements (myoclonus) during induction, which can be prevented by premedication with opioids or benzodiazepines. * **PONV:** It has a high incidence of Postoperative Nausea and Vomiting (PONV). * **Avoidance:** Due to adrenal suppression, it is generally avoided as a continuous infusion in the ICU.

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: Which of the following neuromuscular blocking agents can be safely administered to a patient with combined hepatic and renal failure?

Atracurium. ### Explanation The correct answer is **Atracurium**. #### Why Atracurium is the Correct Choice The primary challenge in patients with combined hepatic and renal failure is the inability to metabolize and excrete drugs through traditional organ-dependent pathways. Atracurium (and its isomer Cisatracurium) is unique because it undergoes **Hofmann Elimination** and **Ester Hydrolysis**. * **Hofmann Elimination:** A spontaneous, non-enzymatic degradation that occurs at physiological pH and temperature. * **Ester Hydrolysis:** Breakdown by non-specific plasma esterases. Because these processes are independent of liver and kidney function, the duration of action remains predictable even in multi-organ failure. #### Why Other Options are Incorrect * **Vecuronium:** Primarily undergoes hepatic metabolism and biliary excretion (approx. 40-50%) with significant renal clearance. Its duration is prolonged in both liver and kidney disease. * **Pancuronium:** A long-acting relaxant primarily excreted unchanged by the kidneys (up to 80%). It is strictly contraindicated in renal failure due to the risk of profound "recurarization." * **Mivacurium:** While metabolized by plasma cholinesterase, its clearance is significantly delayed in patients with liver disease (due to decreased enzyme production) and renal failure. #### High-Yield Clinical Pearls for NEET-PG * **Cisatracurium** is more potent than atracurium and produces less **Laudanosine** (a metabolite of atracurium that can cause CNS excitation/seizures) and less histamine release. * **Drug of Choice:** For renal/hepatic failure, Cisatracurium is often preferred over Atracurium due to its better side-effect profile, though both use Hofmann elimination. * **Temperature/pH Sensitivity:** Since Hofmann elimination is temperature and pH-dependent, the block may last longer in patients with **hypothermia** or **acidosis**.

Q: Which of the following is associated with highly lipid-soluble anesthetic agents?

Potent anesthetic action. ### Explanation The correct answer is **A. Potent anesthetic action**. This question is based on the **Meyer-Overton Hypothesis**, which states that the potency of an anesthetic agent is directly proportional to its lipid solubility. 1. **Why Option A is correct:** The primary site of action for general anesthetics is the lipid bilayer of neuronal membranes or hydrophobic pockets of membrane proteins. Agents with high lipid solubility (measured by the **Oil:Gas Partition Coefficient**) can easily cross the blood-brain barrier and concentrate in the neuronal lipids. Therefore, the higher the lipid solubility, the lower the **Minimum Alveolar Concentration (MAC)** required to produce anesthesia, signifying higher potency. 2. **Why other options are incorrect:** * **B. Potent analgesic action:** Analgesia is a specific component of anesthesia. While some potent agents (like Methoxyflurane) have analgesic properties, others (like Halothane) are potent anesthetics but poor analgesics. * **C. Excellent muscle relaxant action:** Most volatile anesthetics provide some degree of skeletal muscle relaxation, but this is not directly proportional to lipid solubility. Neuromuscular blockers are required for "excellent" relaxation. * **D. Least respiratory depression:** In fact, most potent inhalational anesthetics (except Ketamine and Ether) typically cause dose-dependent respiratory depression. ### High-Yield NEET-PG Pearls: * **Potency ∝ Lipid Solubility** (Meyer-Overton Rule). * **Potency ∝ 1 / MAC** (Lower MAC = Higher Potency). * **Speed of Induction ∝ 1 / Blood:Gas Partition Coefficient** (Lower solubility in blood = Faster induction and recovery). * **Most Potent Inhalational Agent:** Methoxyflurane (Lowest MAC). * **Least Potent Inhalational Agent:** Nitrous Oxide (Highest MAC).

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.

Q: Which of the following inhalational anesthetics is known for smooth induction?

Isoflurane. **Explanation:** The smoothness of induction with an inhalational anesthetic is primarily determined by its **irritability to the airways** (pungency) and its **blood-gas solubility**. **Why Isoflurane is the Correct Answer:** Isoflurane is characterized by its relatively low blood-gas partition coefficient (1.4), which allows for a faster rise in alveolar concentration compared to older agents. While it has a mildly pungent odor, in the context of this specific question (comparing it to Ether, Halothane, and Enflurane), it is clinically favored for its stability and predictable induction profile. *Note: In modern practice, Sevoflurane is the gold standard for smooth mask induction due to its non-pungency; however, among the provided options, Isoflurane is the preferred choice.* **Analysis of Incorrect Options:** * **A. Ether:** Highly irritating to the respiratory tract. It causes significant salivation, coughing, and laryngospasm, making induction prolonged and "stormy." * **B. Halothane:** While non-pungent and historically used for pediatric induction, it is associated with "Halothane Hepatitis" and sensitizes the myocardium to catecholamines, leading to arrhythmias. It is no longer the first choice for "smooth" induction in modern exams. * **D. Enflurane:** It is pungent and can trigger seizure-like activity (epileptiform EEG) at high concentrations, making it unsuitable for a smooth, safe induction. **High-Yield NEET-PG Pearls:** * **Sevoflurane:** The agent of choice for **pediatric mask induction** (sweet-smelling, non-pungent). * **Desflurane:** The most pungent agent; cannot be used for induction as it causes breath-holding and laryngospasm. * **Nitrous Oxide:** Has the lowest potency (MAC 104%) but the fastest induction due to the **Second Gas Effect**. * **Induction Speed:** Inversely proportional to the blood-gas solubility (Lower solubility = Faster induction).

Question 1

Which type of anesthesia is preferred for nasal septoplasty?

Accepted Answer

General anesthesia

Answer

Local infiltration

Answer

Propofol sedation

Answer

No anesthesia required

Question 2

Which of the following drugs inhibits the enzyme 11-beta-hydroxylase responsible for cortisol synthesis?

Accepted Answer

Etomidate

Answer

Thiopentone

Answer

Propofol

Answer

Ketamine

Question 3

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 4

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 5

The action of intravenous thiopentone is terminated by which mechanism?

Accepted Answer

Redistribution

Answer

Rapid renal excretion

Answer

Oxidation

Answer

Conjugation

Question 6

Which of the following neuromuscular blocking agents can be safely administered to a patient with combined hepatic and renal failure?

Accepted Answer

Atracurium

Answer

Vecuronium

Answer

Pancuronium

Answer

Mivacurium

Question 7

Which of the following is associated with highly lipid-soluble anesthetic agents?

Accepted Answer

Potent anesthetic action

Answer

Potent analgesic action

Answer

Excellent muscle relaxant action

Answer

Least respiratory depression

Question 8

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

Accepted Answer

Altitude

Answer

Premedication

Answer

Age

Answer

Drugs

Question 9

Which agent potentiates the action of succinylcholine?

Accepted Answer

Nitrous oxide

Answer

Sevoflurane

Answer

Isoflurane

Answer

Halothane

Question 10

Which of the following inhalational anesthetics is known for smooth induction?

Accepted Answer

Isoflurane

Answer

Ether

Answer

Halothane

Answer

Enflurane

General Anesthesia — MCQs

General Anesthesia — MCQs

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