Comparison of Tramadol and Pethidine for Postanesthetic Shivering in Elective Cataract Surgery

Background: Postoperative shivering is a common event of unknown etiology with an incidence of 5-65%. This study intended to compare the efficacy of tramadol with that of pethidine in controlling postanesthetic shivering. Methods: This double-blind clinical trial was performed on 300 consecutive patients underwent general anesthesia for elective cataract surgery. Intravenous tramadol 1 mg/kg or pethidine 0.5 mg/kg was administered for alternate subjects who developed postanesthetic shivering. They were monitored in the recovery room for 1 hour and the cessation time of shivering, recurrence of the event, duration of recovery, respiratory depression, nausea, vomiting, and arterial O2 saturation were recorded. Results: One hundred and twenty patients (40%) had postanesthetic shivering. In the tramadol group, shivering terminated within 8 minutes after injection (mean 5 min). They had not recurrence of shivering, respiratory depression, reduction in SpO2 and nausea or vomiting during recovery. In the pethidine group, shivering terminated within 13 minutes (mean 9 min) after injection, but in 10 patients it recurred after 30 minutes. In this group 28 patients had respiratory depression, reduction in SpO2, nausea and vomiting but none of them needed any medication. Conclusion: Tramadol is superior to pethidine as it induced a faster termination of postanesthetic shivering and did not entail adverse effects on the respiratory system and SpO2, recurrence of shivering or nausea and vomiting. Easy availability and minimum monitoring requirements are other advantages of tramadol. Keywords: Postoperative Shivering, General Anesthesia, Postoperative Complications, Tramadol, Pethidine.