Background and Aims Sciatic nerve block is widely used alone or in association with other nerve blocks for lower limb surgeries. For below knee surgical procedures distal sciatic nerve block is frequently used. When long acting local anaesthetic such as Bupivacaine is administered irrespective of nerve localization technique complete sensory and motor block are often associated with slow onset of time which is usually 20 - 60 minutes.This study aimed to evaluate and compare the onset of action of sciatic nerve block when given proximal to its bifurcation and immediately after its bifurcation into Tibial and Common peroneal nerves under ultrasound guidance.

Methods Ultrasound guided sub paraneural popliteal sciatic nerve block was performed in 50 patients undergoing lower extremity surgeries. These patients were randomly divided into group A and group B. Where in group A, patients received 20 ml of 0.5% Bupivacaine 8 cm above the bifurcation and in group B, patients received 20 ml of 0.5% Bupivacaine immediately after the bifurcation of sciatic nerve into Tibial and Common peroneal nerves. The performance time and adverse events were recorded.

Results Patients in group A had shorter onset of both sensory and motor block compared to group B which is statistically significant.

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Abstract B19 Figure 2

Total time taken to perform sciatic nerve block was comparable between the groups.

Conclusions Popliteal sciatic nerve block given at pre bifurcation has faster onset of action compared to post bifurcation and block performance time was comparable and independent of BMI in both the groups