Age, minimum alveolar anesthetic concentration, and minimum alveolar anesthetic concentration-awake

Two defining effects of inhaled anesthetics (immobility in the face of noxious stimulation, and absence of memory) correlate with the end-tidal concentrations of the anesthetics. Such defining effects are characterized as MAC (the concentration producing immobility in 50% of patients subjected to a noxious stimulus) and MAC-Awake (the concentration suppressing appropriate response to command in 50% of patients; memory is usually lost at MAC-Awake). If the concentrations are monitored and corrected for the effects of a-e and temperature, the concentrations may be displayed as multiples of MAC for a standard age, usually 40 yr. This article provides an algorithm that might be used to produce such a display, including provision of an estimate of the effect of nitrous oxide.