Brachial Plexus Blockade Causes Subclinical Neuropathy

摘要

Nerve injury following surgery performed under peripheral nerve blockade may be caused by the block (direct trauma by the needle, local anesthetic or adjuvant neurotoxicity, ischemic injury secondary to pressure and volume of local anesthetic, local inflammatory reaction, and hematoma formation secondary to vascular penetration10) and surgical factors (surgical tissue damage, tourniquet injury, postoperative swelling, and intraoperative positioning). Prolonged neuropathy after regional anesthesia is fortunately rare, and reported incidence in the literature ranges from 0.04% to 0.6%.1,5,6 However, those studies rely on the reporting by patients of subjective symptoms.Data suggest that patients with preexisting neuropathy could be more sensitive to nerve injury,4,7,8 and the question of whether it is safe to perform nerve blocks in patients with preexisting neuropathy is not settled.9,11,12 As a first step in investigating this question, we decided to study patients without preexisting neuropathy following peripheral nerve blocks using Semmes-Weinstein monofilament testing to detect subclinical neuropathy. Semmes-Weinstein monofilament testing is a threshold dependent method of measuring changes in light touch, which is thought to be a very sensitive indicator of neuropathy.2 Therefore, it could potentially uncover small sensory deficits that might otherwise not be noticed by the patient or be apparent on gross sensory examination. In this study, we measured monofilament sensibility before the brachial plexus nerve block and at the first postoperative visit. Control groups were tested at the same time points and included the nonoperated hand and general anesthesia (GA) cohort. We hypothesized that postoperative monofilament testing on the extremity that received a block would reveal diminished sensation at a rate higher than that of the control groups.