A 25-year-old patient is undergoing general anesthesia with sevoflurane. The anesthesiologist wants to ensure adequate depth. What is the definition of MAC (Minimum Alveolar Concentration)?

• A The alveolar concentration that produces unconsciousness in 50% of patients
• B The alveolar concentration that prevents movement in response to surgical incision in 95% of patients
• C The alveolar concentration that prevents movement in response to surgical incision in 50% of patients ✓
• D The alveolar concentration that produces amnesia in 95% of patients

Explanation

MAC is defined as the minimum alveolar concentration of an inhaled anesthetic at 1 atmosphere that prevents movement in response to a surgical incision in 50% of subjects. It is the standard measure of anesthetic potency. The 95% value prevents movement in 95% of patients but is not the definition of MAC. Unconsciousness and amnesia are not the endpoints used to define MAC.

Reference: Miller's Anesthesia, 9th ed.

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Written and medically reviewed by the StethoPrep medical team.