Effect of timing of intraoperative administration of paracetamol on postoperative shivering: A randomised double-blind controlled trial

Background and Aims: Paracetamol (PCM) has an anti-shivering effect and may also exacerbate intraoperative hypothermia. This study compares the incidence of shivering as the primary outcome and the incidence of perioperative hypothermia (<36 degrees C) and the time to the analgesic requirement as secondary outcomes when PCM was administered after induction of anaesthesia or towards the end of surgery.Methods: In this randomised study, 225 adult patients of either gender undergoing elective surgical procedures under general anaesthesia with an expected duration of surgery of 1-4 h were studied. They received intravenous (IV) PCM 15 mg/kg (maximum 1 g) immediately after anaesthesia induction (Early PCM group), 30 min before completion of surgery (Late PCM group) or no PCM (Control group). IV morphine 0.1 mg/kg was administered for analgesia in all three groups. The Chi-square test and repeated measures analysis of variance followed by Tukey's test were used for statistical analysis.Results: The incidence of shivering was lower in Late PCM (12%) than in Early PCM (29.3%) (P = 0.009) and Control groups (30.6%) (P = 0.005). The incidence of postoperative hypothermia was also significantly lower in the Late PCM group than in the Early PCM (P = 0.002) and Control groups (P = 0.016). Early PCM and Control groups did not significantly differ. The number of patients requiring postoperative analgesia was smaller, and the time to the analgesic requirement was longer in Late PCM compared to other groups.Conclusion: Administration of IV PCM 30 min before completion of surgery results in a lower incidence of postoperative shivering and hypothermia when compared to PCM administered after induction of anaesthesia or no PCM.