MAC by Age — Modern Anesthesia

Agent

Age-corrected MAC

End-expired volume % in oxygen.

MAC at 40 yr— %

—

MAC at patient age— %

Set age above

MAC-awake— %

Set age above

Nitrous oxide

Inspired nitrous oxide %

N₂O MAC at patient age—

N₂O share of 1 MAC—

Volatile for 1.0 MAC total— %

Set age above and enter nitrous oxide %

The N₂O denominator is age-corrected, not a fixed 104. Capped at 79 % to leave 21 % inspired oxygen.

Table — sevoflurane

1 yr—

10 yr—

20 yr—

40 yr—

60 yr—

80 yr—

Sources

Age correction and MAC at 40 yr: Mapleson WW. Br J Anaesth 1996;76(2):179–185.

—

Iso-MAC charts: Nickalls RWD, Mapleson WW. Br J Anaesth 2003;91(2):170–174 — Eq. 6 age-corrects the nitrous oxide MAC before taking the fraction, as here.

MAC-awake 0.34: Katoh T, et al. Anesth Analg 1993;77(5):1012–1017; Eger EI 2nd. Anesth Analg 2001;93(4):947–953.

Nitrous oxide MAC 104 %: Hornbein TF, et al. Anesth Analg 1982;61(7):553–556. Additivity of MAC fractions is an approximation.

Paediatric: the equation is fitted from 1 yr, so nothing is computed below that. Lerman J, et al. Anesthesiology 1994;80(4):814–824 — sevoflurane MAC 3.3 % in neonates, about 2.5 % in children, and only about 20 % lower in 60 % nitrous oxide where additivity predicts about 58 %.