No additional analgesic effect of intra-articular morphine or bupivacaine compared with placebo after elective knee arthroscopy

Background: Intra-articular pain prophylaxis is a controversial measure, adding costs although the benefits are still disputed. We wanted to evaluate the effects of intra-articular opioid or local anaesthesia or a combination of the two on postoperative analgesia and analgesic consumption after elective knee arthroscopy. Methods: 107 patients with little or no preoperative pain and a minor surgical procedure were studied in a prospective, randomized double-blind design. The patients received midazolam 0.03 mg/kg intravenously before induction of general anaesthesia with fentanyl 1-2 mu g/kg and propofol 2.0 mg/kg intravenously. Anaesthesia was maintained by a total intravenous technique with propofol infusion supplemented with alfentanil 10 mu g/kg when needed. The patients breathed oxygen/air through a laryngeal mask. By the end of the surgery they received 20 ml of test drug into the knee-joint: Group I (BM):20 ml of bupivacaine 2.5 mg/ml with 3 mg of morphine; Group II(B): 20 ml of bupivacaine 2.5 mg/ml; Group III (M): 20 ml isotonic saline with 3 mg morphine; Group IV (P): 20 ml of isotonic saline (placebo). Results: There were no significant differences between the groups in: time to first analgesic administered, analgesic consumption during the pre-or post-discharge period, nausea, somnolence, side-effects or postoperative pain perception during the first week. Conclusions: Intra-articular administration of morphine or bupivacaine is not indicated after elective knee-arthroscopy in patients with minor pre-operative pain and a small surgical trauma.