A volatile anaesthetic agent has an oil:gas partition coefficient of 97 and a blood:gas partition coefficient of 0.45. Which property best explains the rapid emergence from anaesthesia seen with this agent?

• A Low oil:gas partition coefficient
• B High minimum alveolar concentration
• C High vapour pressure at room temperature
• D Low blood:gas partition coefficient ✓

Explanation

The blood:gas partition coefficient determines the rate of equilibration between alveolar and arterial partial pressures; a low value (as seen with desflurane at 0.45) means little agent dissolves in blood, so alveolar concentration rises and falls quickly — enabling rapid induction and rapid emergence. The oil:gas coefficient determines potency (MAC), not kinetics of onset/offset. The MAC value affects depth of anaesthesia required, not speed of recovery.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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