Background and Objectives. Two techniques, single versus double injection, for blocking the sciatic nerve via the classical (Labat) approach were prospectively evaluated for onset and efficacy of block in 50 adult patients undergoing lower extremity surgery. The tibial, common peroneal, and posterior femoral cutaneous nerves were evaluated at 5, 10, 15, 20, 30, and 45 minutes after the initial injection of local anesthetic. Motor function was used to assess the block of the tibial and common peroneal nerves while pinprick response was used to assess block of the posterior femoral cutaneous nerve.

Methods. Group 1 (n = 25) received a single injection of 20 mL of an amide-ester solution (1% lidocaine/0.2% tetracaine) with epinephrine 1:200,000 when either component of the sciatic nerve (tibial or peroneal) was identified with the aid of a peripheral nerve stimulator. Group 2 (n = 25) received two 10 mL injections of the same solution with the tibial and peroneal components of the sciatic nerve being identified and injected separately (through the same skin wheal in serial fashion by withdrawing and redirecting the needle). The two groups were compared at each of the time intervals with analysis of variance.

Results. Group 2 (double injection) showed faster onset and better efficacy (P < .05) at all time intervals evaluated.

Conclusions: The double injection technique for sciatic nerve block via the classical approach results in a more rapid onset and increased efficacy of block than that of the single injection technique.