Prophylactic low dose ketamine infusion for prevention of shivering during spinal anesthesia: A randomized double blind clinical trial

BACKGROUND AND AIMS: Regional anesthesia is known to produce perioperative hypothermia and shivering. We aimed to evaluate if prophylactic low dose ketamine bolus followed by infusion would prevent intraoperative and postoperative shivering under spinal anesthesia. MATERIAL AND METHODS: Sixty patients belonging to American Society of Anaesthesiologists (ASA) 1 and 2 undergoing abdominal and lower limb surgery were randomized to receive either 0.2 mg/kg iv of ketamine bolus followed by infusion 0.1 mg/kg/hr (Group K) or5 ml of saline followed by 0.1 ml/kg/hr solution (Group S) as an infusion throughout the period of surgery. The incidence of shivering was the primary outcome of the study with degree of sedation and the hemodynamic profile between the two groups being the secondary outcomes. Hemodynamics (Heart rate, Mean Blood Pressure and temperature), Grade of shivering and grade of sedation were assessed intraoperatively and for grade of shivering and sedation two hours postoperatively. Repeated measures Analysis of Variance (ANOVA) was used to compare the hemodynamic variables and Chisquare test/Fisher's exact test to compare the grades of shivering and sedation between the two groups. RESULTS: Intraoperative shivering was seen in eighteen patients in saline group (58.06%) and only with four patients (13.79%) with ketamine group (P < 0.001). Post operative shivering was also significantly less in ketamine group compared to saline (P = 0.01). Also, patients who received ketamine had significant sedation in the intraoperative period (P < 0.001). CONCLUSION: Prophylactic low dose ketamine administered as a small bolus followed by an infusion was effective in preventing both intraoperative and postoperative shivering.