Remifentanil combined with low-dose ketamine for postoperative analgesia of lower limb fracture: a double-blind, controlled study

ObjectiveTo investigate the adjuvant effect of intra-operative andpostoperative low-dose ketamine administration to remifentanil consumption in patient-controlled analgesia (PCA) for lower limb fracture.MethodsA total of 200 patients with lower limb fracture receiving the surgery were randomly divided into 4 groups. In Groups A, B and C, patients received 0.5 mg/kg ketamine infusion under general anesthesia, and ketamine in a dose of 0.1 mg/kg, 0.05 mg/kg, 0.01 mg/kg per hour continuously for 24 hours after surgery, respectively. The control group (Group D) received an equivalent volume of normal saline only. With 20 μg/ml remifentanil in normal saline, postoperative PCA was administered with a background infusion at 2 ml/h following 2 ml as a loading dose and 1ml demand dose with a 3-minute lockout period. Remifentanil consumption, 11-point visual analog scale (V AS) scores, global satisfaction score (GSS), and side effects were also recorded by the acute pain service.ResultsCumulative PCA remifentanil consumption in Groups A and B were (1378±377) μg and (1531±402) μg, significantly lower than (1807±510) μg and (1838±523) μg in Groups C and D (P < 0.01). VAS scores in Groups A and B were significantly lower than those in Groups C and D (P < 0.01). In the first 12 hours after operation, GSS was improved (P <0.01). No respiratory depression was observed. No significant difference in side effects was observed among groups.ConclusionLow-dose ketamine can relieve postoperative pain and moderately decrease remifentanil consumption for PCA, with no obvious side effects of ketamine.