Abstract: Objective To observe the dose-effect relationship and side effects caused by epidural ketamine for patients after surgical intervention for knee stiffness (SIKS). Methods 80 patients undergoing SIKS at one knee joint under combined spinal and epidural anesthesia were randomly divided into 4 groups. Patients in these groups would receive analgesia respectively provided by femoral nerve block (FNB)(group C, n=20), FNB combined with 0.15 mg/kg epidural ketamine (group K1, n=20), FNB combined with 0.2 mg/kg epidural ketamine(group K2, n=20), and FNB combined with 0.25 mg/kg epidural ketamine (group K3, n=20). When spinal anesthesia was finished, the corresponding dose of ketamine was injected in patients in groups K1, K2, and K3 and 0.9% sodium chloride was injected in group C via an epidural catheter. After the operation, a catheter was left in the femoral nerve sheath and the solution of 60 mg ropivacaine in 30 ml (0.2%) was injected. All patients were performed rehabilitation therapy at postoperative 8, 24, 32, and 48 h and the same ropivacaine solution was injected in the femoral nerve sheath before each rehabilitation therapy started. Visual analogue score (VAS), active range of motion (AROM) of the suffered knee joint, and side effects were observed. Results There were 73 patients enrolled in the final statistic analysis. At postoperative 8 h, the VAS scores were lower in groups K1, K2 and K3 than in group C (P<0.05). At postoperative 24 h, 32 h, and 48 h, the VAS scores were lower in groups K2 and K3 than in groups C and K1 (P<0.05). AROM was larger in groups K2 and K3 than in groups C and K1. patients appeared psychiatric symptoms in group K3. Conclusion Small dose of epidural ketamine is a feasible method for analgesia in early rehabilitation therapy and the dose of 0.2 mg/kg is effective and safe.

Key words: ketamine, small dose, epidural, surgical intervention for knee stiffness, rehabilitation therapy