Signs of inflammation after sciatic nerve block in pigs

Introduction of nerve stimulators for peripheral nerve blocks did not eliminate the risk of persisting neurologic sequelae (1–4). This is not surprising because every puncture of the neurovascular sheath carries the risk of direct nerve damage with the needle’s tip. Although it is possible to cause paresthesia without the ability to produce a motor response (5,6), the rationale of peripheral nerve stimulation is based on the hypothesis that the distance between the needle’s tip and the nerve is reflected by the actual current. Thus, motor responses elicited with a very low current may suggest a direct needle tip contact, and a forceful injection of drugs in this setting may risk nerve damage. There are no studies demonstrating the potential relationship between the electric current required for the desired motor response before injection of the local anesthetic and subsequent alternations of the nerve. Accordingly, we assessed the integrity of the sciatic nerve histologically 6 h after a block when a motor response was still obtained with a current 0.2 mA versus nerve stimulation with an intensity between 0.3 and 0.5 mA in a pig model.