100+ Free CMSA Diploma in Anaesthesia DA(SA) Practice Questions

Explanation: Hyperthermia increases central metabolic rate and neuronal activity, thereby increasing MAC requirements by approximately 5% for every degree Celsius rise above normal body temperature. Hypernatremia and sympathomimetic states also increase MAC.

Explanation: Desflurane has a blood-gas partition coefficient of 0.42, which is lower than sevoflurane (0.65), isoflurane (1.4), and halothane (2.54). A lower blood-gas solubility coefficient means less drug is dissolved in blood, allowing alveolar partial pressure (FA) to rapidly approach inspired partial pressure (FI), leading to rapid onset and offset.

Explanation: After a single intravenous bolus, propofol rapidly equilibrates across the blood-brain barrier due to high lipophilicity. Awakening within 5 to 10 minutes occurs primarily because of rapid redistribution of propofol from the highly perfused vessel-rich group (brain, heart) into the vessel-intermediate group (skeletal muscle, fat), reducing brain tissue concentration below the hypnotic threshold.

Explanation: Etomidate causes dose-dependent adrenocortical suppression by reversibly inhibiting 11-beta-hydroxylase, the enzyme that converts 11-deoxycortisol to cortisol and 11-deoxycorticosterone to aldosterone in the adrenal cortex. A single induction dose can suppress cortisol response to ACTH for up to 24 hours.

Explanation: Ketamine produces dissociative anaesthesia and analgesia primarily by non-competitively binding to the phencyclidine site inside the open channel of N-methyl-D-aspartate (NMDA) ionotropic glutamate receptors in the brain and spinal cord, inhibiting excitatory glutamatergic transmission.

Explanation: Cisatracurium (an isomer of atracurium) undergoes non-enzymatic Hofmann elimination (pH- and temperature-dependent retro-Michael addition) in plasma and tissues. It produces minimal histamine release and is the muscle relaxant of choice in patients with severe renal or hepatic impairment.

Explanation: Sugammadex is a modified gamma-cyclodextrin molecule structured with a lipophilic core and hydrophilic exterior. It selectively encapsulates aminosteroid relaxants (rocuronium > vecuronium) in plasma in a 1:1 ratio, rapidly lowering free intravascular concentrations and creating a concentration gradient that draws drug off the neuromuscular junction.

Explanation: Remifentanil contains an ester linkage susceptible to rapid degradation by non-specific plasma and tissue esterases. Its context-sensitive half-time remains constant at approximately 3-5 minutes regardless of infusion duration, allowing precise titratability and rapid recovery.

Explanation: A rightward shift of the oxyhemoglobin dissociation curve signifies reduced hemoglobin-oxygen affinity and an increased P50 value. This is driven by elevated PCO2, raised temperature, increased hydrogen ion concentration (acidosis/low pH - Bohr effect), and elevated red cell 2,3-DPG levels.

Explanation: Morphine is metabolized in the liver to morphine-3-glucuronide (M3G, 60%) and morphine-6-glucuronide (M6G, 10%). M6G is a potent mu-opioid receptor agonist with greater analgesic and sedative potency than parent morphine. Both metabolites are excreted by the kidney; in renal failure, M6G accumulates significantly, causing profound sedation and life-threatening respiratory depression.