EDAIC Basic Sciences 5 — Questions and Answers
Question 1: Which phase of hepatic drug metabolism involves oxidation, reduction, and hydrolysis reactions via cytochrome P450 enzymes?
- Phase I (Correct answer)
- Phase II
- Phase III
- Phase IV
Correct answer: Phase I
Phase I metabolism introduces or exposes functional groups via CYP450-mediated oxidation/reduction/hydrolysis, often producing metabolites more reactive than the parent drug.
Question 2: In the context of neuromuscular monitoring, a train-of-four (TOF) ratio of less than 0.9 indicates:
- Residual neuromuscular blockade (Correct answer)
- Complete reversal of blockade
- Depolarizing block pattern
- Phase II block from succinylcholine
Correct answer: Residual neuromuscular blockade
A TOF ratio <0.9 indicates incomplete recovery and is associated with clinically significant residual paralysis including impaired airway protective reflexes.
Question 3: Ketamine's unique cardiovascular stimulating properties are primarily mediated by:
- Central sympathetic nervous system stimulation (Correct answer)
- Direct myocardial beta-1 agonism
- Inhibition of vagal tone
- Peripheral alpha-2 adrenoceptor activation
Correct answer: Central sympathetic nervous system stimulation
Ketamine indirectly increases heart rate and blood pressure by stimulating central sympathetic outflow and inhibiting catecholamine reuptake, masking its direct myocardial depressant effects.
Question 4: The concentration of CO2 at the end of a normal tidal exhalation (PETCO2) is approximately how much less than PaCO2 in a healthy adult?
- 2–5 mmHg less (Correct answer)
- 10–15 mmHg less
- Equal to PaCO2
- 5–10 mmHg more
Correct answer: 2–5 mmHg less
The normal Pa-ETCO2 gradient is 2–5 mmHg due to alveolar dead space diluting end-tidal CO2; this gradient widens with V/Q mismatch or increased dead space.
Question 5: Which factor most significantly determines the rate of inhalational anesthetic induction (speed of rise of FA/FI)?
- Blood:gas partition coefficient of the agent (Correct answer)
- Oil:gas partition coefficient
- Molecular weight of the agent
- Vapor pressure at room temperature
Correct answer: Blood:gas partition coefficient of the agent
A low blood:gas partition coefficient means the agent is poorly soluble in blood, so alveolar partial pressure rises quickly toward inspired concentration, speeding induction.
Question 6: The primary buffer system responsible for buffering CO2 in the blood is:
- Bicarbonate buffer system (CO2/HCO3-) (Correct answer)
- Phosphate buffer system
- Protein buffer system (hemoglobin)
- Ammonia buffer system
Correct answer: Bicarbonate buffer system (CO2/HCO3-)
The bicarbonate system is quantitatively most important for CO2 buffering in plasma; CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3- with carbonic anhydrase catalyzing the reaction in erythrocytes.
Question 7: Neostigmine reverses non-depolarizing neuromuscular blockade by which mechanism?
- Inhibiting acetylcholinesterase, increasing ACh at the NMJ (Correct answer)
- Directly displacing the muscle relaxant from nicotinic receptors
- Stimulating motor neuron acetylcholine release
- Activating muscarinic receptors on muscle fibers
Correct answer: Inhibiting acetylcholinesterase, increasing ACh at the NMJ
Neostigmine inhibits acetylcholinesterase, preventing ACh breakdown and increasing its concentration at the neuromuscular junction, competitively overcoming the non-depolarizing block.
EDAIC Basic Sciences 5
Which phase of hepatic drug metabolism involves oxidation, reduction, and hydrolysis reactions via cytochrome P450 enzymes?