LATE INTRAOPERATIVE CLONIDINE ADMINISTRATION PREVENTS POSTANESTHETIC SHIVERING AFTER TOTAL INTRAVENOUS OR VOLATILE ANESTHESIA

Postoperative administration of clonidine is an effective treatment fo r shivering. However, the ability of this drug to stop postanesthetic shivering when administered intraoperatively remains controversial. Fu rthermore, the relative efficacy of clonidine during isoflurane and pr opofol anesthesia remains unknown. We therefore evaluated the incidenc e of postanesthetic shivering in patients given clonidine during nitro us oxide/isoflurane or propofol anesthesia. Because clonidine is an an algesic, we also evaluated postoperative pain and analgesic requiremen ts. We studied 60 patients undergoing elective ear or nose surgery. Ge neral anesthesia was induced with 2.0 mg/kg propofol, 1.5 mu g/kg fent anyl, and 0.1 mg/kg vecuronium. General anesthesia was maintained with isoflurane and 70% nitrous oxide in one group of patients; in the oth er, a continuous infusion of propofol (8 mg . kg(-1). h(-1)) was admin istered (without nitrous oxide). Five minutes before tracheal extubati on, patients in each group were randomly assigned to receive saline, p lacebo, or 3 mu g/kg clonidine intravenously. Postanesthetic shivering was evaluated by a blind investigator. Postoperative pain was assesse d using a visual analog stale. Postoperative shivering was observed in 53% of the patients given isoflurane without clonidine and in 13% of the patients given propofol without clonidine. No patient given clonid ine shivered. Clonidine administration significantly reduced postopera tive pain. The incidence of postanesthetic shivering was significantly less after propofol anesthesia than after isoflurane/nitrous oxide an esthesia. However, a late intraoperative bolus administration of 3 mu g/kg clonidine prevents postoperative shivering in patients given eith er type of anesthesia.