Use of Ondansetron, Ketamine or Their Combination for Prevention of Post- Anesthetic Shivering

Background:Postanesthetic shivering (PAS) isrelativelycommon side-effectof general anesthesia. We examined the preventive effects of ondansetron,ketamineor both on postanesthetic shivering. Patients and Methods:In this prospective, randomized, double-blindcontrolled trial, 120 ASA I-II, patients, undergoing ENTsurgery under general anesthesia were randomly assigned to one of four equal groups receiving either a combination of ondansetron 4mg plus ketamine 0.25 mg/kg (Group OK), ondansetron 8mg (Group O), ketamine 0.5 mg/kg (Group K), normal saline as the control group (Group C), intravenously 20 minutes before the end of surgery. Tympanic temperature and time to extubation were measured. Postanesthetic shivering was graded upon patient’s arrival to the PACU. Sedation and adverse reactions were evaluated. Results:Shivering was observed in 12 patients (40%) in Group C, 3 patients (10%) in group OK, 4 patients (13.3%) in groups O and 3 patients (10%) in group K,however,the difference between group C and all other groups was statistically significant (P < 0.001).The number of patients with a shivering grade of 3 was significantly higher in Group C compared with other groups (P=0.001).The sedation score was significantly higher in group K than the other groups (P = 0.021).The incidence of nausea or vomiting in the ondansetron group (8mg) was 6.7%, which was significantly less compared to other groups(P = 0.0162). Conclusion: a combination of intravenous ondansetron 4mg plus ketamine 0.25 mg/kg is comparable to either ondansetron 8mg IV or ketamine 0.5 mg/kg IV in preventing post-anesthetic shivering in pre-medicated patients undergoing ENT surgery under general anesthesia.