Introduction: Shivering is a common problem faced by an anesthesiologist during intraoperative as well as in postoperative period, specially after sub-arachnoid block (SAB). It is unpleasant and undesirable and is secondary to vasodilation following sympathetic blockade. The present study was designed to evaluate the efficacy of pethidine on postoperative shivering following SAB and to compare its effects with those of tramadol.

Methods: This randomized, prospective study was conducted in American society of anesthesiologists (ASA) grade I and II  patients undergoing surgery under SAB, to compare the efficacy of tramadol  and pethidine for control of shivering. Patients received tramadol or pethidine in a dose of 0.5mg/kg intra-venously after the appearance of shivering. Disappearance of shivering, side-effects as well as hemodynamics were observed at scheduled intervals.

Results: There were a total of 79 patients randomized into two groups. There were 44 patients receiving pethidine (Group P) and the rest 35 receiving tramadol (Group T). Shivering score was significantly lower in Group P at 10, 15, 20, and 30 minutes compared to that in Group T. Sedation score was higher in pethidine group. Adverse effects in terms of nausea and vomiting was significantly higher in Group T.

Conclusion: Pethidine provide better anti-shivering effect then tramadol with less side effects (nausea and vomiting)  but more sedation.