ABSTRACT
BACKGROUND: Postoperative administration of clonidine is an effective treatment for shivering. However, the ability of this drug to stop postanesthetic shivering when administered intraoperatively remains controversial. Furthermore, the efficacy of clonidine during isoflurane and propofol/fentanyl anesthesia remains unknown. We therefore evaluated the incidence of postanesthetic shivering in patients given clonidine during isoflurane/N2O or propofol/fentanyl/N2O anesthesia. METHODS: Sixty patients scheduled for hysterectomy were divided into 4 groups (each group n = 15):(Group 1:isoflurane/clonidine; group 2:isoflurane/saline; group 3:propofol,fentanyl/clonidine; group 4:propofol,fentanyl/saline). The patients of groups 1 and 2 were anesthetized with N2O/O2/isoflurane and in group 3 and 4 with a continuous infusion of propofol (5 10 mg/kg), fentanyl (0.5 microgram/kg) and N2O. Five minutes before tracheal extubation, patients in each group were randomly assigned to receive saline or 2.5 microgram/kg clonidine intravenously. Postanesthetic shivering was evaluated by a blind investigator. We checked mean arterial pressure, pulse, rectal temperature at baseline, immediately after extubation, and subsequently at 5 min intervals for 60 min. RESULTS: Postoperative shivering was observed in 33% of the patients given isoflurane without clonidine and in 13% of the patients given propofol without clonidine (p < 0.05). No patient given clonidine shivered. The incidence of postanesthetic shivering was less after propofol anesthesia than after isofurane/ N2O anesthesia. Clonidine administration 5 minutes before tracheal extubation improved hemodynamic changes without respiratory depression. CONCLUSIONS: A late intraoperative bolus adminstration of 2.5 microgram/kg clonidine prevents postoperative shivering in patients given either type of anesthesia.