Minimum alveolar concentration

Potency is described by the minimum alveolar concentration (MAC) of an agent and lipid solubility by the oil gas solubility coefficient. 

The minimum alveolar concentration of an anaesthetic vapour at equilibrium is the concentration required to prevent movement to a standardized surgical stimulus in 50% of unpremedicated subjects studied at sea level... 

Gion El, Saidman LJ The minimum alveolar concentration in man. Anesthesiology 35 361-364, 1971... 

A Concept of Anesthetic Dose Based on Partial Pressure-Minimum Alveolar Concentration... 

Depth of anesthesia is determined by the concentration of anesthetic agent that reaches the brain. Brain concentration, in turn, depends on the solubility and transport of the anesthetic agent in the bloodstream and on its partial pressure in inhaled air. Anesthetic potency is usually expressed as a minimum alveolar concentration (MAC), defined as the percent concentration of anesthetic in inhaled air that results in anesthesia in 50% of patients. As shown in Table 9.6, nitrous oxide, N2O, is the least potent of the common anesthetics. Fewer than 50% of patients are immobilized by breathing an 80 20 mix of nitrous oxide and oxygen. Methoxyflurane is the most potent agent a partial pressure of only 1.2 mm Hg is sufficient to anesthetize 50% of patients, and a partial pressure of 1.4 mm Hg will anesthetize 95%. 

Petrenko AB, Tsujita M, Kohno T et al. (2007) Mutation of alG T-type calcium channels in mice does not change anesthetic requirements for loss of the righting reflex and minimum alveolar concentration but delays the onset of anesthetic induction. Anesthesiology 106 1177-1185... 

The potency of inhaled anesthetics is defined quantitatively as the minimum alveolar concentration (MAC), which is the concentration of anesthetic gas needed to eliminate movement among 50% of patients challenged by a standardized skin incision. The MAC is... 

A method for determining minimum alveolar concentration of anesthetic in the rat was published... 

Eger et al. (1988) determined minimum alveolar concentration of fluorinated anesthetics in pigs. 

Eger El II, Johnson BH, Weiskopf RB et al. (1988) Minimum alveolar concentration of 1-653 and isoflurane in pigs. Anaesth Analg 67 1174—1176... 

Eger El II, Xing Y, Laster M et al. (2003) Halothane and isofluroane have additive minimum alveolar concentration (MAC) effects in rats. Anesth Analg 96 1350-1353 Fang Z, Gong D, Ionescu P et al. (1997) Maturation decreases ethanol minimum alveolar anesthetic concentration (MAC) more than desflurane MAC in rats. Anaesth Analg 84 852-858... 

Kashimoto S, Furuya A, Nonaka A et al. (1997) The minimum alveolar concentration of sevoflurane in rats. Eur J Anesthesiol 14 359-361... 

Waizer PR, Baez S, Orkin LR (1973) A method for determining minimum alveolar concentration of anesthetic in the rat. Anesthesiol 39 394-397... 

Midazolam decreases the minimum alveolar concentration of halothane needed for general anesthesia... 

Chan, M.T., P. Mainland, and T. Gin. 1996. Minimum alveolar concentration of halothane and enflurane are decreased in early pregnancy. Anesthesiology 85(4) 782-786. 

LeDez, K.M., and J. Lerman. 1987. The minimum alveolar concentration (MAC) of isoflurane in preterm neonates. Anesthesiology 67(3) 301-307. 

Stevens, W.D., W.M. Dolan, R.T. Gibbons, A. White, E.I. Eger, R.D. Miller, R.H. deJong, and R.M. Elashoff. 1975. Minimum alveolar concentration (MAC) of isoflurande with and without nitrous oxide in patients of various ages. Anesthesiology 42(2) 197-200. 

Comparison of the efficacy of inhalational agents is made by measuring the minimum alveolar concentration (MAC) in oxygen required to prevent movement in response to a standard surgical skin incision in 50% of subjects. The MAC of the volatile agent is reduced by the co-administration of nitrous oxide. 

Cyclopropane is an inhalational anesthetic gas. Its minimum alveolar concentration (MAC) is 9.2%. Because of the risk of explosion, it is usually administered by closed circuit (1). 

Gold MI, Abello D, Herrington C. Minimum alveolar concentration of desflurane in patients older than 65 yr. Anesthesiology 1993 79(4) 710-14. 

Four patients with renal dysfunction in an intensive care unit received isoflurane inhalation for sedation for 8-26 days. The concentrations of isoflurane used were 20-50% of the minimum alveolar concentration. Only small increases in fluoride ion concentration, the highest... 

The effects of alfentanil and esmolol on isoflurane requirements for anesthesia have been studied in a randomized trial in 100 patients (22). Alfentanil infusion to a targeted effect site concentration of 50 ng/ml, but not esmolol, reduced the minimum alveolar concentration of isoflurane required to suppress movement to surgical pain by 25%. The combination of esmolol and alfentanil caused a 74% reduction in isoflurane requirements. This study is interesting, because the beta-blocker esmolol had a profound effect on the isoflurane-sparing effects of alfentanil, while having little effect on its own. 

Fahey MR, Sessler Dl, Cannon JE, Brady K, Stoen R, Miller RD. Atracurium, vecuronium, and pancuroninm do not alter the minimum alveolar concentration of halothane in humans. Anesthesiology 1989 71(l) 53-6. 

In 45 adult patients undergoing elective surgery, the 2-adrenoceptor agonist dexmedetomidine in a concentration of 0.7 ng/ml reduced the minimum alveolar concentration of sevoflurane required to suppress movement to skin incision by 17%, but a plasma concentration of 0.39 ng/ml had no effect (58). The larger reductions in isoflurane requirements found in earlier studies of dexmedetomidine were probably due to the use of potent opioids and intravenous induction as part of the anesthetic. 

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