Effect of Early Versus Late Intraoperative Administration of Intravenous Paracetamol on Postoperative Shivering in Patients Undergoing Elective Surgery: A Randomized Trial

ABSTRACT Background and Aim: Postoperative shivering is a common complication following general anaesthesia and may contribute to increased metabolic demand, patient discomfort, and physiological stress. Intravenous paracetamol has been reported to have anti-shivering effects in addition to its established analgesic role; however, the optimal timing of administration for prevention of postoperative shivering remains unclear. This study aimed to evaluate the effect of early versus late intraoperative administration of intravenous paracetamol on the incidence and severity of postoperative shivering in patients undergoing elective surgery under general anaesthesia. Materials and Methods: This prospective, randomized, double-blind clinical trial included 154 adult patients (ASA physical status I–II) undergoing elective surgery under general anaesthesia. Patients were randomized into two groups of 77 each. Group A received intravenous paracetamol 15 mg/kg (maximum 1 g) immediately after induction of anaesthesia, while Group B received the same dose 30 minutes before completion of surgery. The primary outcome was the incidence of postoperative shivering during the first four postoperative hours. Secondary outcomes included severity of shivering, postoperative pain scores, rescue anti-shivering medication requirement, rescue analgesic requirement, perioperative temperature changes, haemodynamic parameters, and adverse events. Results: Among 154 randomized patients, postoperative shivering occurred less frequently in Group B compared with Group A (14.3% vs 36.4%, p=0.002). Severe shivering (Grades 3 and 4) was lower in the late administration group compared with the early administration group (3.9% vs 19.5%, p=0.011). Rescue tramadol requirement was also lower in Group B (3.9% vs 19.5%, p=0.002). Patients receiving late administration had lower postoperative pain scores and reduced rescue diclofenac requirement (7.8% vs 19.5%, p=0.027). Group B demonstrated higher axillary temperatures during the late intraoperative period and early postoperative recovery, while heart rate remained comparable between groups throughout the observation period. Conclusion: Administration of intravenous paracetamol 30 minutes before completion of surgery reduced the incidence and severity of postoperative shivering and improved early postoperative analgesic outcomes compared with administration immediately after induction of anaesthesia. Optimizing the timing of intravenous paracetamol administration may represent a simple and practical strategy to improve perioperative comfort and early postoperative management in patients undergoing elective surgery under general anaesthesia. Keywords: postoperative shivering, effect of paracetamol, general anaesthesia