Determining minimum alveolar anesthetic concentration of halothane in rats: the effect of incremental change in halothane concentration and number of crossovers.

Computer simulations for the technique of estimating minimum alveolar anesthetic concentration (MAC) in patients (quantal design) suggest that incremental concentration changes and the number of crossovers affect MAC. We hypothesized that these variables may also apply to estimating MAC in rats (bracketing design). This study tested that hypothesis and also examined whether these variables might mask differences in MAC between groups in which MAC might be expected to differ (pregnant [P] versus nonpregnant [NP]).