Restoration of baroreflex control of heart rate during recovery from anaesthesia

The effects on baroreflex control of heart rate of halothane or methohexitone used to supplement 67% nitrous oxide in oxygen have been studied in 21 patients. Stable anaesthesia with either agent caused depression of baroreflex sensitivity by more than 50%. The set point of the reflex was also changed by both agents, but in opposite directions. Halothane administration resulted in slower heart rates at lower arterial pressures, whereas the infusion of methohexitone caused faster heart rates at lower arterial pressure. During recovery from anaesthesia, there was a rapid return of baroreflex sensitivity to normal and this was achieved before the patients regained consciousness, with no difference between the two groups. The reflex was reset rapidly and repeatedly during the recovery phase.