In which of the following clinical conditions is the minimum alveolar concentration (MAC) of a volatile anaesthetic INCREASED relative to baseline?
- A Core temperature of 34 degrees Celsius
- B Third trimester of pregnancy
- C Core temperature of 40 degrees Celsius ✓
- D Concurrent therapy with lithium carbonate
Correct answer: C. Core temperature of 40 degrees Celsius
Explanation
Hyperthermia raises MAC, roughly in proportion to the elevation in body temperature, whereas every degree of hypothermia reduces MAC. Pregnancy lowers MAC by up to 30 to 40%, an effect maximal in the first trimester. Lithium potentiates neuromuscular and anaesthetic effects and decreases MAC. Other recognised reducers include opioids, alpha-2 agonists, hypothyroidism, hyponatraemia and increasing age beyond 40 years.
Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.