Efficacy of prophylactic epidural ketamine for reducing shivering in patients undergoing caesarean section with combined spinal-epidural anesthesia

Intravenous ketamine is known to inhibit postoperative shivering; however, at present, there has been little research on whether this effect may be achieved with epidural application. The aim of the present study was to evaluate the efficacy and safety of epidural ketamine as a prophylactic agent to prevent shivering in patients undergoing caesarean section during combined spinal-epidural anesthesia. A prospective, randomized, double-blind study was performed. A total of 60 patients who were undergoing elective caesarean section under combined spinal-epidural anesthesia and had an American Society of Anesthesiologists physical status of I or II were recruited. Patients were randomly allocated to group S (epidural administration of normal saline; n=30) or group K (epidural ketamine 0.5 mg/kg; n=30). An investigator, blinded to the treatment groups, graded postoperative shivering using a 4-point scale and postoperative sedation on a 5-point scale. Operative time, hemodynamic changes and side effects, including hypotension, bradycardia, nausea and hallucinations, were recorded. The results demonstrated that patients' characteristics were not significantly different between groups. Heart rate, peripheral capillary oxygen saturation (SpO(2)) values and Apgar scores at 1 and 5 min also did not differ significantly between groups. The incidence and severity of shivering in group K was significantly reduced compared with group S (P<0.05). The mean arterial pressure (MAP) was significantly different in groups S and K compared with baseline values at 10, 30 and 60 min (P<0.05). Furthermore, MAP values at 10, 30 and 60 min were significantly higher in group K compared with in group S (P<0.05). The results of the present study suggest that epidural administration of prophylactic low-dose ketamine may be an effective strategy for preventing postoperative shivering.