minimum alveolar concentration
The concentration of an inhaled anesthetic agent in the alveoli at which 50% of patients do not move in response to a surgical stimulus; used as a standard measure of inhalational anesthetic potency.
Full Definition
Minimum alveolar concentration (MAC) is expressed as a percentage of one atmosphere and serves as the benchmark unit of potency for volatile anesthetic agents. A MAC of 1.0 represents the alveolar concentration at which half of unpremedicated patients remain motionless during a standardized noxious stimulus. Values are age-dependent, lower in elderly patients and neonates, and additive across agents. In dental anesthesiology editorial contexts, MAC values frequently appear in pharmacology tables and drug comparison discussions. Editors must not confuse the abbreviation with 'maximum allowable concentration' used in occupational health literature.
Usage
Usage note: Abbreviate as MAC after first use; always italicise subscript modifiers (e.g., MAC-awake, MAC-BAR) consistently throughout a document.
In Context
- "Nitrous oxide has a MAC of approximately 104%, meaning it cannot produce surgical anesthesia at atmospheric pressure alone." — Clinical pharmacology review article
- "The protocol specified that sevoflurane be maintained at 0.5 MAC to supplement nitrous oxide sedation." — Dental sedation clinical guideline