Calculators
MAC (Age-Adjusted)
Minimum Alveolar Concentration adjusted to patient age via the Mapleson equation.
MAC(age) = MAC₄₀ × 10^(−0.00269 × (age − 40))
1.0 MAC
2vol %
Reference MAC₄₀ = 2 vol %
MAC awake (~0.34)
0.68vol %
Approximate concentration of return of awareness
Remember: MAC values are additive (e.g., 0.5 MAC sevo + 0.5 MAC N₂O ≈ 1 MAC). MAC ↓ with opioids, benzos, hypothermia, pregnancy, hyponatremia, anemia; ↑ with chronic alcohol use, hyperthermia, sympathomimetics.
References & Further Reading
- 1Journal
Mapleson WW. Effect of age on MAC in humans: a meta-analysis. Br J Anaesth. 1996;76(2):179-185.
- 2Textbook
Gropper MA, Miller RD, Cohen NH, et al., eds. Miller's Anesthesia. 9th ed. Philadelphia: Elsevier; 2020.
Citations are provided to direct further study. Always check the most current edition of guidelines and society recommendations — the information in this chapter is a teaching summary, not primary source material.