Isoflurane's approximate MAC value is which of the following?

• A. 0.8
• B. 1.2
• C. 1.6
• D. 2.0

Answer: (B)

Minimum alveolar concentration is a measure of potency for inhaled anesthetics: it’s the alveolar concentration, at 1 atmosphere, that prevents movement in 50% of patients in response to a standard surgical stimulus. Isoflurane has a MAC in healthy adults of about 1.2% (roughly 1.15–1.2%). This places it between more potent agents (lower MAC values) and less potent ones (higher MAC values). So, the approximate MAC value for isoflurane is around 1.2%.

The other values aren’t consistent with its known potency: a lower value like 0.8% would imply a more potent agent (lower MAC), while higher values such as 1.6% or 2.0% would imply much less potency than isoflurane. MAC can vary with factors like age, opioids, temperature, and pregnancy, but the typical adult MAC for isoflurane remains near 1.2%.