Evaluation the effects of adding ketamine to morphine in intravenous patient-controlled analgesia after orthopedic surgery

BACKGROUND: Intravenous patient-controlled analgesia (PCA) with morphine is commonly used for post-operative pain after major surgery. Ketamine has analgesic property at lower doses, and in combination with opioids it could have synergistic effect. The aim of this study is to determine effects of the addition of ketamine to morphine for PCA after orthopedic surgery. MATERIALS AND METHODS: In this double-blind randomized clinical trial, 60 patients were randomly allocated to receive PCA consisting: Group 1 (morphine 0.2 mg/ml), Group 2 (morphine 0.2 mg/ml + ketamine 1 mg/ml), and Group 3 (morphine 0.1 mg/ml + ketamine 2 mg/ml). In this, anesthesiologists managed study, patients had orthopedic surgery. Assessments were made at 24 h and 48 h post-operatively. Visual analog scale (VAS) was used for recording pain score. PCA morphine use was recorded at 24 h and 48 h. VAS scores over 48 h were analyzed with analysis of variance for repeated measures. Significance level was taken as 0.05. RESULTS: There is no significant difference between demographic information of the three groups (P > 0.05). Control of pain in Group 2 and Group 3 was better than in Group 1 (only morphine) (P = 0.001) but there was no significant difference between Group 2 and Group 3 (P > 0.05). Rate of narcotic consumption in groups 2 and 3 was significantly lower than Group 1 (P < 0.05). CONCLUSION: After orthopedic surgery, the addition of ketamine to morphine for intravenous PCA was superior to Intravenous PCA opioid alone. The combination induces a significant reduction in pain score and cumulative morphine consumption.