Combined saphenous and sciatic catheters for analgesia after major ankle surgery: a double-blinded randomized controlled trial.

Abstract

Continuous sciatic nerve block is used for pain management following major ankle surgery. Pain from the saphenous nerve territory often persists. We conducted a double-blinded randomized placebo-controlled trial to evaluate the effect of a supplementary saphenous catheter in the proximal thigh combined with a popliteal sciatic catheter and single-shot saphenous nerve block after major ankle surgery. Fifty patients received both sciatic and saphenous continuous catheters inserted along the short axis of the nerves with ultrasound-guidance. All patients had an initial sciatic nerve block followed by a continuous sciatic catheter infusion and an initial saphenous nerve block with ropivacaine. Participants were then randomized to infusion of either ropivacaine or isotonic saline in the saphenous catheter for 48 hr postoperatively. The primary outcome was total intravenous morphine consumption during the first 48 hr postoperatively. Secondary outcomes were clinical analgesia, saphenous analgesia, territory of worst pain, and patient satisfaction. Forty-four patients were included in the analysis. The mean (SD) 48-hr morphine consumption was 24.7 (21.6) mg in the intervention group and 27.8 (20.1) mg in the placebo group (P=0.63). The mean difference in 48-hr morphine consumption was 3.0mg (95% confidence interval, -9.7 to 15.7). There were no differences regarding the secondary outcomes. A saphenous catheter with a low-dose continuous infusion of ropivacaine, as an adjunct to a sciatic catheter, had no effect on the postoperative analgesia after major ankle surgery when both catheters were inserted along the short axis of the nerves. This trial was registered at ClinicalTrials.gov (NCT01445210).