The use of Doppler ultrasound to assist with sciatic nerve blocks.

Twenty consecutive patients requiring surgical procedures on a lower extremity received leg blocks using a modification of Labat's classic approach. A Doppler ultrasound pencil probe was used to identify the dominant arterial structure exiting the sciatic notch with the sciatic nerve. A block needle was inserted in the same orientation as the probe until paraesthesias were elicited; then 25 ml of local anesthetic was injected. Successful block was achieved in one or two attempts in 70% of the patients.