Intra-operative remifentanil might influence pain levels in the immediate post-operative period after major abdominal surgery

Backround: Remifentanil, a widely used analgesic agent in anaesthesia, has a rapid onset and short duration of action. In clinical settings, this requires an appropriate pain strategy to prevent unacceptable pain in the post-operative period. The aim of this study was to investigate whether remifentanil had any impact on post-operative pain and opioid consumption after major abdominal surgery. Method: Fifty patients undergoing major abdominal surgery were randomized to receive either remifentanil 0.4 mu g/kg/min or placebo intra-operatively, in addition to basic combined general and epidural anaesthesia, in this double-blind study. Patients received patient-controlled analgesia with morphine for 24 h post-operatively. Morphine consumption, assessment of pain at rest and during coughing, side-effects and levels of sensory block were recorded during the first 24 h post-operatively. Result: Twenty-one patients receiving remifentanil and 18 patients receiving placebo completed the study. The median visual analogue scale (VAS) score at rest from 0 to 2 h was significantly increased in the remifentanil group [40 mm (27-61 mm)] vs. placebo [13 mm (3-35 mm)] (P < 0.05). No significant differences in morphine consumption, VAS score during coughing or adverse effects were observed between the groups. Conclusion: The results are weak and difficult to interpret. They could indicate that a high dose of remifentanil added to otherwise sufficient combined general and epidural anaesthesia may induce opioid-induced hyperalgesia and/or clinically acute opioid tolerance after major abdominal surgery; however, as no significant differences could be observed between the groups after 2 h post-operatively, the clinical relevance of these observations is questionable.