Which statement regarding the effect of chronic ethanol consumption on MAC is correct?

Which statement regarding the effect of chronic ethanol consumption on MAC is correct?

• A. Chronic ethanol consumption increases MAC
• B. Chronic ethanol consumption decreases MAC
• C. No effect
• D. Effect depends on the specific volatile agent

Answer: (A)

Chronic ethanol exposure leads to tolerance to CNS depressants, so higher amounts of inhaled anesthetic are needed to achieve the same immobility response. The brain adapts by increasing excitatory pathways (such as NMDA receptor activity) and reducing inhibitory GABAergic effects, making it harder for a given concentration of volatile agent to produce the desired anesthetic effect. That’s why MAC is increased with chronic alcohol use. Acute intoxication, by contrast, lowers MAC because the CNS is already depressed. The change is not specific to one volatile agent; the increased MAC is a general effect seen across volatile anesthetics.

Chronic ethanol exposure leads to tolerance to CNS depressants, so higher amounts of inhaled anesthetic are needed to achieve the same immobility response. The brain adapts by increasing excitatory pathways (such as NMDA receptor activity) and reducing inhibitory GABAergic effects, making it harder for a given concentration of volatile agent to produce the desired anesthetic effect. That’s why MAC is increased with chronic alcohol use. Acute intoxication, by contrast, lowers MAC because the CNS is already depressed. The change is not specific to one volatile agent; the increased MAC is a general effect seen across volatile anesthetics.