The lateral approach to the sciatic nerve at the popliteal fossa: One or two injections?

It has not been proven whether one or multiple nerve stimulations and injec tions provide a higher rate of complete sensory block in both major sciatic nerve sensory distributions below the knee when a popliteal sciatic nerve block is performed using the lateral approach. This prospective, randomized , single-blinded study compared the success rate of the sciatic nerve block using this approach when one or both major components of this nerve (i.e., tibial nerve and common peroneal nerves) are stimulated in 50 patients und ergoing foot or ankle surgery. In Group 1 STIM, 24 patients received a sing le injection of 20 mL of a mixture of 2% lidocaine and 0.5% bupivacaine wit h 1:200,000 epinephrine after foot inversion had been elicited. In Group 2 STIM (n = 26), 10 mt of the same solution was injected after stimulation of each sciatic nerve component. For patients with complete sensory motor blo ck, there was no difference in onset between groups. However, Group 2 STIM showed a greater success rate compared with the Group 1 STIM (2 STIM: 88% v s 1 STIM :54%; P = 0.007). When two stimulations were used, the onset time of anesthesia in the cutaneous distribution of the common peroneal nerves w as shorter than in the tibial nerve (17.5 vs 30 min; P < 0.0001). We conclu de that a two-stimulation technique provides a better success rate than a s ingle-injection technique when a popliteal sciatic nerve block is performed using the lateral approach with 20 mt of local anesthetic. Implications: A better success rate is achieved with a double stimulation technique than w ith a single injection for the sciatic nerve block via the lateral approach at the popliteal fossa when 20 mt of local anesthetics is used.