MORPHINE DOES NOT AFFECT THE AWAKENING CONCENTRATION OF SEVOFLURANE

This study was designed to determine whether morphine 0.1 mg, kg-1 iv given intraoperatively altered the end-tidal concentration of sevoflur ane which is associated with eye opening to verbal command. We studied 24 healthy ASA physical status I patients to determine whether morphi ne, or placebo administered about 60 min before the end of surgery aff ected recovery from sevoflurane/oxygen anaesthesia. During anaesthesia no other anaesthetics or drugs were given. After surgery, end-tidal s evoflurane concentration was reduced gradually at the rate of less tha n 0.01% . min-1. The end-tidal concentration at the time patients coul d respond to verbal command was recorded as MACawake. The MACawake was 0.58 +/- 0.12% (mean +/-SD)for the control group to whom placebo had been administered and 0.57 +/- 0.11% for morphine group to whom morphi ne had been administered In both groups, the MACawake decreased with a ge, and the ratio to age-adjusted sevoflurane MAC was 0.31 +/- 0.04 (m ean +/- SD) for the control group and 0.30 +/- 0.04 for the morphine g roup. The ratio had no correlation with age It is concluded that the a wakening concentration of sevoflurane during recovery from anaesthesia is not affected by analgesic doses of morphine 0.1 mg . kg-1 iv admin istered intraoperatively.