[Continuous versus single-dose sciatic nerve block to complement a femoral block after total knee replacement surgery: a randomized clinical trial].

Summary INTRODUCTION: Performing a sciatic nerve block to complement a continuous femoral nerve block for anal- gesia after total knee arthroplasty is a subject of con- troversy. We compared the efficacy of a continuous sciatic nerve block to that of a single-dose block of the same nerve combined with a continuous femoral nerve block. MATERIAL AND METHODS: Patients received a con- tinuous femoral nerve block by infusion of 0.2% ropiva- caine, 0.4 mL·kg -1 , plus patient controlled analgesia and were randomized to receive a sciatic nerve block either by continuous infusion (0.5% ropivacaine, 20 mL, plus continuous infusion of 5 mh -1 ) or by a single 20 mL dose of 0.5% ropivacaine. The stimulating catheters remained indwelling for 72 hours after the operation. The main outcome measure was assessment of postoperative pain on a verbal numerical scale from 0 (no pain) to 10 (grea- test pain) at rest and upon movement. RESULTS: The pain assessments upon movement of the operated joint were significantly greater after 24 hours in the group receiving a single dose of ropivacaine to block the sciatic nerve. The back of the knee was most often named as the location of pain. No adverse effects related to the analgesic technique were recorded, and the level of satisfaction was higher among patients receiv- ing the continuous sciatic nerve block. CONCLUSION: Twenty-four hours after total knee replacement surgery, better analgesia was achieved with a continuous sciatic nerve block than with a single-dose block combined with a continuous femoral nerve block.