Purpose: Sciatic nerve block is useful for surgery below the knee both intra- and postoperatively. Several techniques to insert a catheter at the knee level or higher have been described but need mobilization (lateral decubitus) of the patient. We describe novel landmarks, using a high lateral approach, to block the sciatic nerve without moving the patient.
Clinical features: One hundred seven ASA I, II and III ASA patients scheduled for major foot or ankle surgery were studied prospectively. With patients awake and lying in the supine position, the catheter was introduced along novel landmarks in the peri-nervous adipose space using specifically designed material and nerve stimulation (< 0.5 mA). After a negative test dose (1% lidocaine with 1/200.000 epinephrine), 10 mL of 0.5% bupivacaine and 10 mL of 2% lidocaine were injected. Thirty minutes after performance of the block, the cutaneous and dermatomal sensory blockade were assessed using cold and pinprick tests while motor block was assessed using a modified Bromage scale. Complications and incidents were recorded. The tibial and superficial peroneal nerve were always blocked, while the deep peroneal and postero-femoral cutaneous nerves were blocked in only 97% and 83% of the patients, respectively. Anesthesia, was always present in the dermatome L5 and in the S1 dermatome in 98% of the patients. No major incidents or complications were noted. Three catheters could not be inserted and the anesthestic solution was injected through the needle.
Conclusion: The lateral technique for sciatic nerve anesthesia and catheter insertion allows patients to remain in the supine position for performance of the block and catheter insertion, and results in a high rate of homogeneous anesthesia and a low incidence of side effects.