Determination and applications of MAC

Abstract

Since the description of MAC, its determining variables have been studied in detail. A long list of physiologic and pharmacologic interventions in various species of animals that will or will not alter anesthetic requirements has thus been established. The MAC has emerged as a remarkably consistent index of anesthetic potency, which for any given anesthetic will vary within a twofold range in widely different classes of animals. The uses of MAC are many and varied. For example, MAC has been used to test theories of anesthesia and the therapeutic indexes of various agents with respect to vital organ depression. Controversy has arisen over these uses of MAC. In man, MAC is essentially the midpoint of a cumulative frequency distribution. The quantal nature of MAC, strictly speaking, does not allow pharmacologic comparisons between agents at MAC multiples or fractions, but many studies have suggested the clinical and experimental validity of doing so. Despite these problems, MAC remains the only widely accepted measure by which comparisons between anesthetics can be made or the relative margins of safety established. 173 references are cited.