Background: Treatment with ketamine and pethidine is effective in postoperative shivering. The aim of this study was to compare the efficacy of low-dose prophylactic ketamine with that of pethidine or placebo in preventing postoperative shivering.
Methods: A prospective randomized double-blind study involved 90 ASA I and II patients undergoing general anaesthesia. Patients were randomly allocated to receive normal saline (Group S, n=30), pethidine 20 mg (Group P, n=30) or ketamine 0.5 mg kg(-1) (Group K, n=30) intravenously 20 min before completion of surgery. The anaesthesia was induced with propofol 2 mg kg(-1), fentanyl 1 microg kg(-1) and vecuronium 0.1 mg kg(-1). It was maintained with sevoflurane 2-4% and nitrous oxide 60% in oxygen. Tympanic temperature was measured immediately after induction of anaesthesia, 30 min after induction and before administration of the study drug. An investigator, blinded to the treatment group, graded postoperative shivering using a four-point scale and postoperative pain using a visual analogue scale (VAS) ranging between 0 and 10.
Results: The three groups did not differ significantly regarding patient characteristics. The number of patients shivering on arrival in the recovery room, and at 10 and 20 min after operation were significantly less in Groups P and K than in Group S. The time to first analgesic requirement in Group S was shorter than in either Group K or Group P (P<0.005). There was no difference between the three groups regarding VAS pain scores.
Conclusion: Prophylactic low-dose ketamine was found to be effective in preventing postoperative shivering.