Material and Method: The present study was a prospective, randomized, double-blind, controlled clinical trial involving 183 ASA I-III patients, aged 18 to 65 years whom underwent orthopedic surgery with general anesthesia. The patients were randomly allocated to receive either ketamine 0.25 mg/kg (Group K, n = 91) or normal saline (Group P, n = 92) 20 minutes before the completion of surgery. The tympanic temperature was measured before the induction of anesthesia, 30 minutes after induction, and before administration of the study drugs. An investigator, blinded to the patients’ group affiliation, graded post anesthetic shivering using the Crossley and Mahajan scale. The primary outcome was to compare incidence of shivering on each group in recovery room. The secondary outcome was side effect of ketamine. Statistical analyses were performed using program R version 3.1.0. A p-value of <0.05 was considered statistically significant.

Results: The patient characteristics of the two groups were similar, and the number of patients with observed shivering in both groups was not statistically significantly different (Group K = 13 (14.28%) and Group P = 15 (16.30%), p = 0.42). Furthermore, in both groups, no patient suffered from hallucination, and the other complications were not statistically different.

Conclusion: At the recovery room, no significant efficacy difference between low-dose ketamine (0.25 mg/kg) and placebo in the prevention of post operative shivering in patients who underwent orthopedic surgery was observed. Other factors such as preload warm intravenous fluid, using active warming during surgery and control of the room temperature may help prevent shivering.

Keywords: Low-dose ketamine, Prevention, Post anesthetic shivering, Orthopedic surgery, Side effect