Age-related iso-MAC charts for isoflurane, sevoflurane and desflurane in man

Br J Anaesth. 2003 Aug;91(2):170-4. doi: 10.1093/bja/aeg132.

Abstract

Background: The motivation for this study was the current difficulty in estimating the total age-related MAC for a patient in a clinical setting.

Methods: Age-related iso-MAC charts for isoflurane, sevoflurane and desflurane were developed for the clinically useful MAC range (0.6-1.6), age range 5-95 yr, and put in a convenient form for use by practising anaesthetists. The charts are based on Mapleson's meta-analysis (1996) of the available MAC data and can be used to allow for the contribution of nitrous oxide to the total MAC.

Results: The charts indicate the influence of age on anaesthetic requirements, showing, for example, that a total MAC of 1.2 using isoflurane and nitrous oxide 67% in oxygen requires an end-expired isoflurane concentration of only 0.25% in a patient of 95 yr vs 1% in a 5-yr-old patient. Colleagues found the charts to be helpful and simple to use clinically.

Conclusions: The iso-MAC charts show clearly how patient age can be used to guide the choice of end-expired agent concentration. They also allow a consistent total MAC to be maintained when changing the inspired nitrous oxide concentration, thereby reducing the chance of inadvertent awareness, particularly at the extremes of age.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Aging / metabolism*
  • Algorithms*
  • Anesthetics, Inhalation / administration & dosage
  • Anesthetics, Inhalation / pharmacokinetics*
  • Child
  • Child, Preschool
  • Desflurane
  • Drug Administration Schedule
  • Humans
  • Isoflurane / administration & dosage
  • Isoflurane / analogs & derivatives*
  • Isoflurane / pharmacokinetics
  • Methyl Ethers / administration & dosage
  • Methyl Ethers / pharmacokinetics
  • Middle Aged
  • Pulmonary Alveoli / metabolism*
  • Reference Values
  • Sevoflurane

Substances

  • Anesthetics, Inhalation
  • Methyl Ethers
  • Sevoflurane
  • Desflurane
  • Isoflurane