[Determination of median effective dose of lidocaine to control the onset time of sciatic nerve blockade using up-and-down sequential method].

Objective: To determine the median effective dose (ED50) of 2% lidocaine to control the onset time of sciatic nerve blockade within 15 min by using 2% lidocaine and 0.75% ropivacaine 10 ml.

Methods: Fifty patients underwent sciatic nerve blockade and lumbar plexus blockade for operations of unilateral lower extremities.