The Effect of Low Dose i.v. Ketamine in Combination with Epidural Morphine on Postoperative Pain

Background: The purpose of this study was to evaluate the effect of low dose i.v. ketamine in combination with epidural morphine on postoperative pain after gastrectomy. Methods: 40 patients scheduled for elective gastrectomy were investigated in a randomized study. All patients received epidural morphine (0.05 mg/kg) and bupivacaine (0.25%) as a bolus dose of 10 ml 40 min prior to skin incision. In addition, patient- controlled epidural analgesia (PCEA) with epidural bupivacaine (0.125%) and morphine (0.1 mg/ml) (bolus dose 1 ml, continuous infusion 1 ml/h, lock out interval 15 min) was offered from the time after 10 ml bolus dose. In the ketamine group, ketamine 0.5 mg/kg was administered 10 min prior to skin incision and then maintained continuously until skin closure at a dosage of 10/kg/min. In the second group anesthesia was induced with thiopental sodium 4 mg/kg, midazolam 0.5 mg/kg, vecuronium 0.1 mg/kg and maintained with 66% -O2, 1-3 vol% enflurane. The intensities of spontaneous pain and of coughing associated pain were measured using a visual analogue scale. Cumulative morphine consumption was measured at 2, 6, 12, 24, 48 h after surgery. Side effects were evaluated at 48 h after surgery. Results: VAS and cumulative morphine consumption at 2, 6, 12, 24, 48 h postoperatively showed no statistical differences between the two groups, and no statistical differences in side effects were observed at 48h after surgery. Conclusions: We were unable to demonstrate any additional analgesic effect of low dose i.v. ketamine in combination with epidural morphine and bupivacaine.