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

Objective: To investigate the adjuvant effect of intraoperative and postoperative low-dose ketamine administration to remifentanil consumption in patient-controlled analgesia (PCA) for lower limb fracture.

Methods: A 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 microgram/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 (VAS) scores, global satisfaction score (GSS), and side effects were also recorded by the acute pain service.

Results: Cumulative PCA remifentanil consumption in Groups A and B were (1378+/-77) microgram and (1531+/-402) microgram, significantly lower than (1807+/-510) microgram and (1838+/-523) microgram 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.

Conclusion: Low-dose ketamine can relieve postoperative pain and moderately decrease remifentanil consumption for PCA, with no obvious side effects of ketamine.