Post spinal anaesthesia shivering is known to be a frequent complication and has a reported incidence of 40 to 70 percent. Shivering is defined as the involuntary and oscillatory muscular activity that increases the metabolic rate by two to three fold to maintain core temperature by increasing heat production.

This study will be a randomized clinical study to compare the efficacy of intravenous ondansetron and intrathecal fentanyl in evaluating temperature changes and shivering in patients undergoing elective lower segment caesarean sections under spinal anaesthesia.

A total of 252 patients aged 18 to 40 years of ASA physical status I and II undergoing elective lower segment caesarean section will be enrolled in the study. The patients will be divided into two groups of 126 each. The study drug will be prepared in a 5 mL syringe by an anaesthesiologist not directly involved in the study to maintain double blinding. Group F will receive intrathecal fentanyl along with 10 mg 2 mL of 0 point 5 percent hyperbaric bupivacaine and 4 mL intravenous normal saline. Group O will receive 4 mL 0 point 1 mg per kg intravenous ondansetron following intrathecal injection of 10 mg 2 mL of 0 point 5 percent hyperbaric bupivacaine. The operating room temperature will be maintained at an ambient temperature of around 24 to 26 degrees Celsius.

Vital parameters including temperature, blood pressure, heart rate, and SpO2 will be recorded preoperatively and intraoperatively. The time of onset of shivering, its grade, and the time of disappearance of shivering will be recorded. In case shivering is not controlled by the study drugs, 0 point 5 mg per kg of intravenous tramadol will be used as rescue therapy. The collected data will be analysed using appropriate statistical methods. Quantitative data will be analysed using the Student t test and qualitative data will be analysed using the Chi square test. A p value less than 0 point 05 will be considered statistically significant.