minimum alveolar concentration


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minimum alveolar concentration (MAC)

[min′iməm]
the smallest concentration of a gas that is measured in the alveoli of the lungs, which can provide a state of general anesthesia.

minimum alveolar concentration

Abbreviation: MAC
A measure of the relative potency of an anesthetic agent, specifically, the concentration of the agent in exhaled air that will prevent 50% of people from moving when they are exposed to a painful or noxious stimulus, such as one they might experience during surgery.
See also: concentration
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References in periodicals archive ?
Cumulative duration of "triple low" state of low blood pressure, low bispectral index, and low minimum alveolar concentration of volatile anesthesia is not associated with increased mortality.
Mean minimum alveolar concentration equivalent23 used by anaesthetists (corrected for age and specific for volatile agent) was 0.
Minimum alveolar concentrations in man on awakening from methoxyflurane, isoflurane, ether and fluroxene anesthesia: MAC awake.
After a period of time in which the partial pressure of sevoflurane in the brain would have equilibrated with the alveolar partial pressure (6,7), the patient showed clinical signs of adequate anaesthesia and had an end-tidal sevoflurane concentration of more than 1 minimum alveolar concentration, but the entropy monitor still indicated an awake state.
Opioid agents significantly reduce the minimum alveolar concentration of potent inhaled anaesthetics required to facilitate intubation and improve overall intubating conditions during sevoflurane anaesthesia (5,6).
Several studies have shown a decreased maternal minimum alveolar concentration (MAC) for inhalational agents during pregnancy (1-3).
Estimates of effect-site levels should be similar to minimum alveolar concentration (MAC) values, which are determined after allowing time for equilibrium.

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