What does MAC stand for in inhalant anesthesia, and how does it relate to potency?

• A. Minimum Alveolar Concentration
• B. Maximum Anesthetic Concentration
• C. Mean Alveolar Concentration
• D. Monitored Anesthetic Concentration

Answer: (A)

MAC stands for Minimum Alveolar Concentration. It is the end-tidal/alveolar concentration of an inhaled anesthetic that prevents movement in 50% of subjects in response to a standardized painful stimulus. This makes MAC a direct measure of potency: the lower the MAC, the more potent the agent because a smaller concentration is needed to blunt the response. MAC is a population parameter and can be influenced by species, age, temperature, pregnancy, and other factors. It’s about how much anesthetic is required to suppress movement to a stimulus, not a single animal’s depth of anesthesia. The other terms don’t reflect this standard definition, so they aren’t used to describe potency.