Comparison of prophylactic use of meperidine and two low doses of ketamine for prevention of post-anesthetic shivering: A randomized double-blind placebo controlled trial*

BACKGROUND Postanesthetic shivering is one of the most common complications of anesthesia. We compared the efficacy of meperidine and two low doses of ketamine with placebo to prevent postanesthetic shivering after general anesthesia. METHODS This was a prospective, randomized double-blind placebo controlled clinical trial involving 120 ASA I-II patients aging 20-50 years, undergoing endoscopic sinus surgery with general anesthesia. Patients were randomly allocated to receive meperidine 0.4 mg/kg (Group M, n = 30), ketamine 0.3 mg/kg (Group K(1), n = 30), ketamine 0.5 mg/kg (Group K(2), n = 30), or normal saline (Group N, n = 30) 20 minutes before completion of the surgery. Tympanic temperature, blood pressure, and heart rate were measured before and immediately after induction of anesthesia, 30 minutes after induction, and before administration of the study drugs. The drugs were prepared and diluted to a volume of 2 ml and presented as coded syringes. An investigator, blinded to the groups, graded postanesthetic shivering using a four-point scale. Statistical analyses were performed using Statistical Package for Social Sciences (SPSS) Windows version 16. A p-value < 0.05 was considered statistically significant. RESULTS Patient characteristics of the four groups were similar. The number of patients with observed shivering in groups was 0, 3, 1, and 9 in Groups M, K(1), K(2) and N, respectively. The difference between groups M, K(1), and K(2) with Group N was statistically significant. However, differences between groups M and K(1), M and K(2), and K(1) and K(2) were not significant. The number of patients with a shivering score of 2 or 3 was higher in Group N compared with other groups. CONCLUSIONS Prophylactic use of low doses of intravenous ketamine (0.3 or 0.5 mg/kg) was found to be effective to prevent postanesthetic shivering. However, administration of 0.3 mg/kg ketamine lowered the rate of hallucination as compared with 0.5 mg/kg.