MAC and solubility: principles of volatile anaesthetic action

MAC defined

MAC was introduced by Eger and colleagues in 1965. It measures a single quantitative endpoint, immobility: the alveolar concentration at which 50% of people do not move in response to a surgical stimulus. End-tidal concentration is used as the measure of alveolar, and in turn central nervous system, anaesthetic level, and MAC is the standard for comparing volatile anaesthetic potency.^[7]

Immobility (MAC) is produced by anaesthetic actions on the spinal cord. In vivo work suggests GABA-A, acetylcholine, potassium, 5-HT3, opioid and alpha-2 receptors may not mediate MAC, whereas glycine, NMDA and sodium channels remain credible candidates.^[13]

References14ShowHide

1. [1]Gan Z, et al. The Median Effective Concentration of Sevoflurane for I-Gel Laryngeal Mask Insertion in Unpremedicated Children Aged 1-10 Years: A Prospective Concentration-Finding Study Pediatr Discov, 2026.PMID 42021953
2. [2]Hollingworth D, et al. Volatile anaesthetics modulate voltage-gated sodium channel function at a site directly linked to channel gating Nat Commun, 2026.PMID 42321197
3. [6]Bajwa SJS, et al. Indian expert consensus on intra-operative consciousness monitoring using processed electroencephalogram-based indices: A Delphi-based approach Indian J Anaesth, 2026.PMID 42145302
4. [7]Lobo SA, Ojeda J, Dua A, et al. Minimum Alveolar Concentration. 2024.PMID 30422569
5. [8]Mapleson WW Effect of age on MAC in humans: a meta-analysis. British journal of anaesthesia, 1996.PMID 8777094
6. [9]Eger EI 2nd Desflurane animal and human pharmacology: aspects of kinetics, safety, and MAC. Anesthesia and analgesia, 1992.PMID 1524237
7. [10]Esper T, Wehner M, Meinecke CD, et al. Blood/Gas partition coefficients for isoflurane, sevoflurane, and desflurane in a clinically relevant patient population. Anesthesia and analgesia, 2015.PMID 25393590
8. [11]Taheri S, Eger EI 2nd A demonstration of the concentration and second gas effects in humans anesthetized with nitrous oxide and desflurane. Anesthesia and analgesia, 1999.PMID 10475324
9. [12]Korman B, Mapleson WW Concentration and second gas effects: can the accepted explanation be improved? British journal of anaesthesia, 1997.PMID 9175984
10. [13]Sonner JM, Antognini JF, Dutton RC, et al. Inhaled anesthetics and immobility: mechanisms, mysteries, and minimum alveolar anesthetic concentration. Anesthesia and analgesia, 2003.PMID 12933393
11. [14]Shandong New Time Pharmaceutical Co., Ltd. SEVOFLURANE liquid — prescribing information. DailyMed, 2026.Source
12. [15]Henry Schein, Inc. SUPRANE (desflurane) liquid — prescribing information. DailyMed, 2026.Source
13. [16]Piramal Critical Care, Inc. TERRELL (isoflurane) liquid — prescribing information. DailyMed, 2026.Source
14. [17]Antkowiak B How do general anaesthetics work? Die Naturwissenschaften, 2001.PMID 11482433