Minimum alveolar concentration (MAC) of a volatile anaesthetic is increased in which one of the following conditions?

• A Chronic alcohol consumption ✓
• B Pregnancy
• C Hypothermia
• D Concurrent lithium therapy

Explanation

MAC reflects CNS requirement for the volatile agent and is reduced by anything that depresses the CNS: hypothermia, pregnancy, increasing age, acute alcohol intake, opioids, benzodiazepines and alpha-2 agonists all lower it. Chronic alcohol consumption induces hepatic enzymes and produces cross-tolerance at the neuronal level, so MAC is increased. Lithium potentiates neuromuscular blockade but has no clinically important effect on MAC. Pregnancy lowers MAC by roughly a third.

Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.