Continuous subgluteus sciatic nerve block after orthopedic foot and ankle surgery: comparison of two infusion techniques.

BACKGROUND AND OBJECTIVE: To compare continuous infusion or a patient-controlled technique for postoperative analgesia after foot surgery, using a new subgluteus approach for continuous sciatic nerve block.

METHODS: Fifty healthy patients, undergoing orthopedic foot surgery, received a continuous sciatic nerve block using a new subgluteus approach. All blocks were placed with the aid of a nerve stimulator using a 10-cm, 18-gauge insulated Tuohy needle. After either plantar flexion or dorsiflexion of the operated foot was elicited at < or = 0.5 mA, 20 mL of 0.75% ropivacaine was injected incrementally using repeated aspiration tests, then followed by the introduction of a 20-gauge epidural catheter. Postoperatively, 0.2% ropivacaine was infused with either a 10 mL/h continuous infusion (group Continuous, n = 25) or with a 5 mL/h basal rate with 5 mL bolus every 60 minutes (group patient-controlled analgesia [PCA], n = 25). Intraoperative analgesic supplementation, as well as postoperative pain relief, morphine consumption, incidence of complication, and patient satisfaction were recorded by an observer unaware of group assignment.

RESULTS: The sciatic catheter was successfully placed in all patients. Intravenous fentanyl supplementation (dose range, 50 to 150 microg) was required in 4 patients in each group, but no patient required general anesthesia. Catheter dislocation was reported in 2 patients (4%). The quality of pain relief was good in both groups, and none experienced complications. Nine patients of the Continuous group (37%) and 7 patients of the PCA group (29%) required rescue morphine analgesia because of pain in the femoral dermatomes (P =.76). Ropivacaine consumption was 240 mL in the Continuous group (range, 200 to 240 mL) and 140 mL in the PCA group (range, 120 to 290 mL) (P =.0005). Patient acceptance was good in both groups.

CONCLUSIONS: The continuous subgluteus sciatic nerve block represents an easy and reliable option for postoperative analgesia after foot surgery; using a patient controlled rather than a continuous infusion technique reduces the consumption of local anesthetic solution without affecting the quality of pain relief.