The decrease of the minimum alveolar anesthetic concentration produced by sufentanil in rats

The anesthetic potency of sufentanil was established by determining its effect on the minimal alveolar anesthetic concentration (MAC) of halothane. Each of eight selected doses of sufentanil was administered to a group of four to five mechanically ventilated rats anesthetized with halothane. Sufentanil was administered as a constant infusion preceded by an intravenous bolus dose that was three times that of the infusion rate per minute. The tail-clamp technique was used to establish control MAC and the MAC of halothane with sufentanil. Increasing sufentanil dosages were nonlinearly related to reductions in the MAC of halothane. A sigmoidal dose-response curve was described. An abrupt, steep response follows the initial upward deflection of the curve with an additional 62% MAC reduction occurring between doses of 1 X 10(-5) mg X kg-1 X min-1 and 1 X 10(-4) mg X kg-1 X min-1. Essentially complete anesthesia was seen at the latter dosage. No significant adverse side effects were seen with sufentanil at doses up to 1 X 10(-2) mg X kg-1 X min-1.