Ketamine and tramadol for the prevention of shivering during spinal anaesthesia.

Anaesthesia and surgery promote significant thermal disorder in the human body. Spinal anaesthesia causes lower limb vasodilation and redistribution of body heat from central to the peripheral compartments.This was a prospective, randomised, double-blind clinical study to compare the effectiveness of IV ketamine and tramadol in the prevention of shivering associated with spinal anaesthesia. We prospectively studied 150 ASA classification I and II patients between 18 and 70 years old scheduled for any elective surgery performed under spinal anaesthesia. Patients were randomly allocated to receive either prophylactic IV ketamine 0.5 mg/kg (Group K), IV tramadol 0.5 mg/kg (Group T) or normal saline as control (Group P) after intrathecal injection of 0.5% hyperbaric bupivacaine 12.5 mg (2.5 ml) and 25 mcg fentanyl. The frequency and degree of shivering, haemodynamic parameters, core body temperature and side effects of the studied drugs were recorded for the first 30 minutes.The incidence of shivering was 8% in Group K, 16% in Group T and 24% in Group P. This result was statistically significant between Groups K and P. Patients from Group K also exhibited significantly higher mean arterial blood pressure and heart rate at 5 and 15 minutes post intrathecal injection while their mean core temperature was also significantly higher. Side effects such as nausea, vomiting, hallucination, agitation and sweating were comparable between all three groups. Patients from Group K however, had significant higher incidence of behavioural changes (blunted affect or catatonic state) and nystagmus.Prophylactic use of IV ketamine 0.5 mg/kg significantly reduced the frequency and the intensity of perioperative shivering associated with spinal anaesthesia but also exhibited some side effects of the drug. Lower doses of prophylactic ketamine should be studied.