Minimum alveolar concentrations (MAC) of halothane and nitrous oxide in swine

To compare anesthetic effects using a swine model, we needed to know the minimum alveolar concentrations (MAC) of halothane and nitrous oxide that produce anesthesia in the pig. This information does not exist in literature. Furthermore, MAC varies considerably among species: by more than 60% for halothane, and by more than 200% for nitrous oxide. Therefore, using eight young swine, we determined mean (+/- SEM) MAC values for halothane (1.25 +/- 0.04% of one atmosphere) and nitrous oxide (277 +/- 18% of one atmosphere). These values are higher than values reported for other mammals. Factors possibly accounting for this variability include interspecies differences, age, body temperature, increased sympathetic activity, and differences in methodology.