What is MAC in anesthesia?

MAC (Minimum Alveolar Concentration) is the concentration of an inhaled anesthetic at 1 atmosphere that prevents movement in 50% of subjects in response to a standardized surgical skin incision. It is a measure of anesthetic potency — the lower the MAC, the more potent the agent.

How does age affect MAC?

MAC decreases with increasing age. The most widely used correction is approximately 6% decrease per decade of life after a peak in early childhood. A 70-year-old patient requires roughly 20–25% less anesthetic than a 40-year-old.

What does MAC-awake mean?

MAC-awake is the MAC at which 50% of patients open their eyes on verbal command. It is typically 0.3–0.5 × MAC. Loss of consciousness occurs at concentrations well below the standard surgical MAC.

What factors increase or decrease MAC?

MAC is increased by hyperthermia, chronic alcohol use, and young age. MAC is decreased by hypothermia, opioids, benzodiazepines, age, pregnancy, hypotension, and acute alcohol intoxication.

Why is nitrous oxide MAC greater than 100%?

Nitrous oxide has a MAC of approximately 104% in adults, meaning it cannot produce surgical anesthesia on its own at normal atmospheric pressure. It is used as an adjunct to reduce requirements for other agents.

Is this tool a substitute for clinical judgment?

No. This tool is an educational reference only. Clinical anesthetic management must be individualized and supervised by a qualified anesthesia provider. MAC values are population averages and do not account for all patient-specific factors.

MAC Anesthetic Helper

Name: MAC Anesthetic Helper
Availability: InStock
Author: Nham Vu

Look up standard MAC values for inhaled anesthetics, calculate age-adjusted MAC, and compare agents side by side.

Age-Adjusted MAC Calculator

Anesthetic Agent

Patient Age (years)

Age range: 1–110 years

Inhaled Anesthetic MAC Reference

Agent	MAC (adult)	MAC-Awake	BP (mmHg)	Notes

Age Correction Guide

Age Range	Correction Factor	Example (Isoflurane)
Infant (6 mo)	×1.20	~1.44%
Child (1–5 yr)	×1.10	~1.32%
Young adult (20–40 yr)	×1.00	1.20%
Middle age (50 yr)	×0.94	~1.13%
Senior (70 yr)	×0.82	~0.98%
Elderly (80 yr)	×0.76	~0.91%

Age correction: ~6% decrease per decade above age 40 (Quasha et al.). Peak MAC occurs in early childhood. Values are approximate population averages.

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Summary

Look up standard MAC values for inhaled anesthetics, calculate age-adjusted MAC, and compare agents side by side.

How it works

Select an inhaled anesthetic agent from the list or view all agents in the comparison table.
Enter the patient age to calculate the age-adjusted MAC.
The tool applies the standard age-correction formula: MAC decreases approximately 6% per decade after age 40.
Review the calculated MAC values and compare agents in the reference table.
Use the results to guide vaporizer settings during general anesthesia.

Use cases

Quick bedside reference for MAC values during anesthesia planning.
Teaching tool for anesthesia residents and students.
Comparing potency of different volatile anesthetic agents.
Calculating age-adjusted MAC for pediatric and elderly patients.
Estimating MAC multiples for depth of anesthesia targets.
Reviewing pharmacology of inhaled anesthetics.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu