A comparative study on the analgesic effect of tramadol, tramadol plus magnesium, and tramadol plus ketamine for postoperative pain management after major abdominal surgery

Abstract

Background: We tested whether, after major abdominal surgery, the addition of magnesium or ketamine to tramadol for intravenous (IV) patient-controlled analgesia (PCA) improved analgesia and lowered pain scores, compared to a PCA containing only tramadol. Methods: Sixty-six patients were allocated randomly to receive a PCA with tramadol alone (T), tramadol plus magnesium (TM) or tramadol plus ketamin (TK), in a double-blind randomized study. Postoperative analgesia was started when the verbal rating scale (VRS) score was 2 or more. Following a loading dose of the study solution (which contained 1mg/kg tramadol), a background infusion of 0.4mg/kg/h was started. Patients were allowed to use bolus doses of 0.2mg/kg every 20min without a time limit. Discomfort, sedation, pain scores, total and bolus PCA tramadol consumption, and side-effects, were recorded for up to 24h after the start of PCA. Results: Pain and discomfort scores were lower (P<0.01) in groups TM and TK at 15, 30, 60 and 120min than in group T. The addition of magnesium or ketamine significantly reduced the consumption of tramadol at 6, 12 and 24h (P<0.01). The incidence of nausea did not differ between the groups. Conclusion: Adding magnesium or ketamine to tramadol improved analgesia and patient comfort and decreased the amount of tramadol required for postoperative pain management after major abdominal surgery. © Acta Anaesthesiologica Scandinavica 46 (2002).