Background: Post­anesthetic shivering (PAS) is distressing for patients and may induce a variety of complications. The neurotransmitter pathways involved in the mechanism of post­anesthetic shivering are complex and poorly understood. We compared the effect of ondansetron ( 5­HT3 ntagonist) and butorphanol (agonist at “Kappa”­receptors and mixed agonist antagonist at mu opioid receptors) on intraoperative core and peripheral temperatures andPAS. Methods:After approval from institutional ethics committee and written informed consent 90 patients of age 18–60 years, ASA I­II, undergoing orthopedic, general or urological surgery were randomized into three groups.In this double­blinded, placebocontrolled, study: Group A(n = 30) received ondansetron 8 mg, Group B (n = 30) received Butorphanol, 25 gm / kg and Group C (n = 30) received saline 4 ml intravenous (IV) immediately before the anesthetic induction. Heart rate (HR), mean arterial pressure (MAP), oxygen saturation (SPO2), core (nasopharynx) and fingertip temperature (dorsum of middle finger) was recorded. Balanced general anaesthesia was induced by propofol 2.5 mg/kg and intubation was done with Vecuronium 0.1mg/kg. Anaesthesia was maintained with 70% N 2O in O2 and propofol infusion. PAS was documented by persons blinded to the study and included trainees in anesthesiology who were unaware of the group assignment. Results: PAS occurred in 19 of 30 (63.3%) patients in Group C (saline), compared with 6 of 30 (20%) in ondansetron group (P = 0.002) and 7 of 30 (23.3%) in butorphanol group (P = 0.004). Within each group, core temperature decreased and peripheral temperature increased significantly, but there were no significant differences among the groups A and B at any time interval. Conclusion: We conclude that both, ondansetron (8 mg) and butorphanol (25  gm / kg) IV given during the induction of anesthesia prevents PAS equally without affecting the core­to­peripheral redistribution of heat during general anesthesia. 

Keywords: Ondansetron; Butorphanol; Post­Anesthetic Shivering; General Anesthesia; Hypothermia.