Minimal alveolar concentration

The minimum alveolar concentration ( English Minimum Alveolar Concentration , abbr .: MAC ) is a term from anesthesiology and describes the anesthetic potency of inhalation anesthetics .

The commonly used MAC ( MAC ₅₀ ) is defined as the alveolar concentration of an inhalation anesthetic at which 50% of patients no longer react (with defensive movements) to a skin incision ("surgical MAC").

Other defined MACs are the MAC ₉₅ (no pain reaction in 95% of patients), the MAC EI (no defensive movements during endotracheal intubation ), the MAC BAR ( block adrenergic response , no reactions of the sympathetic nervous system to pain stimuli) and the MAC awake (Concentration at which 50% of patients open their eyes)

It is given as a percentage of a gas mixture and fluctuates depending on the amount of oxygen added . The MAC is higher in babies, young children, febrile patients and those suffering from alcoholism than in the average patient, while it is lower in pregnant women , in old age, in shock , in anemia , with underactive thyroid ( hypothyroidism ) and with simultaneous use of certain medications such as benzodiazepines or analgesics .

literature

• Eger EI 2nd, Saidman LJ, Brandstater B: Minimum alveolar anesthetic concentration: a standard of anesthetic potency. Anesthesiology . 1965 Nov-Dec; 26 (6): 756-63. PMID 5844267

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