Double-blind comparison of ropivacaine 7.5 mg ml-1 with bupivacaine 5 mg ml-1 for sciatic nerve block

Two groups of 12 patients had a sciatic nerve block performed with 20 ml of either ropivacaine 7.5 mg ml(-1) or bupivacaine 5 mg ml(-1). There was no statistically significant difference in the mean time to onset of complete anaesthesia of the foot or to first request for post-operative analgesia. The quality of the block was the same in each group. Although there was no statistically significant difference in the mean time to peak plasma concentrations the mean peale concentration of ropivacaine was significantly higher than that of bupivacaine. There were no signs of systemic local anaesthetic toxicity in any patient in either group.