Document Type

Presentation

Publication Date

8-21-2009

Abstract

The popliteal nerve block can be performed either proximal to the bifmcation of the sciatic nerve, or distal to the bifmcation, thus blocking both the common peroneal and tibial nerves. Studies have shown equal success rates when comparing the two methods. The purpose of this investigation is to determine if blocking the tibial and common peroneal nerves individually in the popliteal fossa under ultrasound guidance will result in a faster onset time to smgical anesthesia when compared to blocking the sciatic nerve proximal to the bifurcation under ultrasound guidance. A total of 56 patients who underwent foot surgery were randomized to either pre-bifurcation or post bifurcation. The block was then evaluated by a blinded investigator, for pinprick sensitivity and motor blockade beginning at 10 minutes from the injection of the anesthetic, and every three minutes thereafter lmtil the block had completely set. Mean times for sensory and motor score end points were calculated for each group and compared using the Mann-Whitney test. The mean time for complete sensory loss in the tibial distribution for the proximal group was 25.7 minutes, while the mean time for the distal group was 15.9 minutes (difference = 9.8, P < 0.002). The mean times for motor loss on the tibial group was 27.9 and 16.4 minutes respectively (difference = 11.5, P <0.001). The mean times for complete sensory loss in the peroneal distribution were 16.6 minutes for the proximal block and 13.1 for the distal block (difference = 3.5, P = 0.03). The mean times for peroneal motor loss were 15.8 and 12.3 minutes respectively (difference = 3.5, P = 0.05). The authors conclude that injecting anesthetic distal to the bifurcation of the sciatic nerve will result in faster onset to smgical anesthesia when compared to a proximal injection.

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