A comparison of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa

Background: The purpose of this study was to compare anesthetic efficacy an d postoperative analgesia of 0.5% ropivacaine and 1% mepivacaine for sciati c nerve block in the popliteal fossa (popliteal block). Methods: A prospective, double-blind study was carried out in 58 adult pati ents scheduled for outpatient foot or ankle surgery. They were randomized t o receive popliteal block with 40 ml of either 0.5% ropivacaine (group R) o r 1% mepivacaine (group M). An atraumatic, Teflon-coated needle connected t o a neurostimulator was used to make a single puncture using a posterior ap proach. The times to onset of sensory and motor block, and the need for int raoperative sedation were recorded. Before discharge, patients were asked t o document the time to first analgesic use, time to return of full sensatio n in the foot, and their evaluation of the technique. Results: Onset time (mean +/- standard deviation, 95% confidence interval) of both sensory block (6.5 +/- 5.1 min, 4.47-8.49, in group R and 6.2 +/- 3 .7 min, 4.83-7.69, in group M) and motor block (6.6 +/- 4.4 min, 4.81-8.23, in group R and 7.9 +/- 4.1 min, 6.29-9.53, in group M) was similar in both groups. Postoperative analgesia lasted longer in group R (15.2 +/- 5.1 h, 13.25-17.21) than in group M (5.7 +/- 1.8 h, 5.01-6.41; P <0.001). Duration of sensory block was longer in group R (20.7 +/- 6.2 h, 18.51-23.01) than in group M (6.5 +/- 1.7 h, 536-7.16; P <0.001). Acceptance of the anestheti c procedure was similar in both groups. Conclusion: In this study we demonstrated that both 0.5% ropivacaine and 1% mepivacaine for popliteal block produced rapid, effective and safe anesthe sia but postoperative analgesia was more long-lasting with ropivacaine.