ELECTROPHYSIOLOGICAL EVALUATION OF SPINAL REFLEXES DURING EPIDURAL-ANESTHESIA IN AN EXPERIMENTAL-MODEL

We assessed the effects of epidural anesthesia with bupivacaine in the rat by serial recordings of spinal reflexes, The H wave from plantar muscles after electrical stimulation of the sciatic nerve evaluates a large nerve fiber spinal reflex arch, The extensor reflex response rec orded from quadriceps muscle after stimulation of the contralateral ti bial nerve assesses a reflex arch with small fiber afferents, After ep idural injection of 0.2 mL of bupivacaine (0.25%, 0.5%, and 1.0% solut ions) at the L5-L6 vertebral space, nociceptive, H, and extensor refle x responses were abolished within 1-3 min, Duration of complete blocka de lasted 20-80 min, increasing with the anesthetic concentration, and complete recovery occurred after an additional period of 30-40 min. T he responses recovered to amplitudes similar to preanesthesia controls , indicating that there was no damage to the nervous system, This stud y shows that electrophysiological recording and quantitation of nerve reflex responses is a useful and accurate method to evaluate the effic acy of local anesthetic agents. (C) 1996 John Wiley & Sons, Inc.