Background: Ultrasound imaging, an effective tool to localize peripheral nerves, may facilitate block performance. However, its usefulness during popliteal sciatic nerve block has not been assessed.
Methods: In this prospective, randomized, patient-blinded study, we compared the block time (as the primary end-point) of a popliteal sciatic nerve block with double-injection performed using anatomical landmarks and neurostimulation (NS group; n = 30) versus combined ultrasound and neurostimulation guidance (US-NS group; n = 30). Each block procedure was performed by a single operator. Correct needle placement was defined by a minimal stimulating current < or = 0.5 mA, or, in the US-NS group, by mobilization of the nerve by the needle shaft even if the minimal stimulating current > 0.5 mA. Ten milliliter levobupivacaine 0.5% was administered separately on the tibial and common peroneal nerves without needle adjustment to improve the spread of anesthetic in the US-NS group. All procedures were video-recorded, and a maximum of 7 min was allowed to perform the block. Successful block was defined as complete loss of cold sensation in the sciatic distribution and an inability to perform a plantar and dorsal flexion of the foot at 30 min.
Results: Five patients in the NS group and three in US-NS group were excluded from the study for prolonged procedure. Block time was not significantly different between groups. The number of needle passes was lower only for the detection of the first nerve in the US-NS group (1 [1-2] vs 2 [1-6]; P < 0.01). A greater success rate was observed at 30 min in the US-NS group (65% vs 16%; P < 0.001).
Conclusions: Combined ultrasound and neurostimulation guidance does not decrease block time but increases the success rate of popliteal sciatic nerve block observed at 30 min.