[Combined sciatic/3-in-1 block. III. Prilocaine 1% versus mepivacaine 1%]

In a randomized, double-blind study, the efficacy of prilocaine 1% (group 1, 30 patients) was compared to mepivacaine 1% (group 2, 30 patients). All patients had a combined sciatic/femoral block for surgery of the lower extremities; a tourniquet was applied in each case. In each patient the block was done using 50 ml of a 1% solution of local anesthetic: 20 ml for the sciatic and 30 ml for the 3-in-1 block. The time to onset of sensory block was approx. 4 min in both groups; the onset of motor blockade averaged 6 min and after 10-12 and 15 min sensory and motor blockades, respectively, were complete. On the average, patients were pain-free for 254 min with prilocaine and 267 min with mepivacaine. Four of 30 patients (= 13%) in group 1 an 6 of 30 patients (= 20%) in group 2 had an unsatisfactory blockade and had to be supplemented by analgesics or general anesthesia. The finding of a significant correlation between the voltage necessary for stimulation and the efficacy of the blockade underlines the importance of correct stimulation when identifying the nerves.