Postoperative analgesia: morphine and ketamine vs. morphine

O-27 Introduction: Patient controlled analgesia (PCA) with morphine (M) is considered to be the gold standard in postoperative pain treatment. Ketamine (K) has analgesic effects and gives cumulated or potentiated analgesia when associated with M. We studied quality of postoperative pain relief when K is added to M-PCA. Methods: After institutional Ethics Committee approval, 30 patients undergoing abdominal surgery were randomly allocated to either a M-group (n = 15) or a K-group (n = 15). Postoperatively, when a VAS score of 4 or more was reached, a bolus of 3 mg M was administered. Then i.v. PCA with M was started in both groups. The K-group also received a bolus of 1 mg kg−1 K followed by a continuous infusion at a rate of 2.5 μg kg−1 min−1. Vital parameters, pain intensity, M consumption and side-effects were noted at 0, 1, 2, 4, 6, 12, 24, 36 and 48 h after PCA was initiated. The Mann-Whitney U-test, a two-tail paired Student's t-test and ANOVA were used for statistical analysis. Results: Vital parameters and demographic data were comparable in both groups. Both treatments induced good pain relief in all patients. The K-group had significantly lower VAS scores at 1 h. After 48 h morphine consumption was lower in the K-group (28 mg) compared with the M-group (54 mg) (P = 0.0003). Side-effects were reported in 13% in the K-group and in 60% in the M-group. Conclusion: The combination of M and K as compared with M alone provided good pain relief. Both morphine consumption and the incidence of side-effects were significantly reduced in the K-group.