Continuous popliteal sciatic nerve block for outpatient foot surgery - a randomized, controlled trial

Background: A major problem in outpatient foot surgery is severe postoperative pain that is not sufficiently treated by peroral analgesics. Methods: Sixty-three patients underwent foot surgery under spinal anesthesia. Immediately on conclusion of the operation, sciatic and saphenous nerve blocks were performed. The sciatic nerve was blocked in the popliteal fossa with 30 ml of ropivacaine 5 mg ml(-1) and a perineural. catheter was passed through the cannula. The patients were randomized to receive either ropivacaine 2 mg ml(-1) (n = 30) or saline (n = 30) in the catheter through a disposable elastomeric pump with a fixed infusion rate of 5 ml h(-1) for 55 h. Results: Analgesia was excellent until 23 h 44 min (14 h 34 min) in the treatment group and 18 h 16 min (7 h) in the placebo group [mean (SD), P = 0.07]. Thereafter, pain was significantly less in the treatment group on the first and second postoperative days (P = 0.001). Sleep disturbances because of the pain in the foot were experienced by 25% of the treatment group on the first night at home and by 50% of the control group (P=0.29). There were no differences between the groups in their need for rescue opioid medication. None of the patients had any major problem with the catheter or pump, and none had any toxic effect referable to the technique. Conclusion: This randomized, double-blind study shows that continuous blockade of the sciatic nerve in the popliteal fossa reduces postoperative pain and has no untoward effects in a patient group known to experience severe pain after ambulatory surgery.