Effects of epidural analgesia on scalp-recorded somatosensory evoked potentials to posterior tibial nerve stimulation

The effect of epidural analgesia with plain bupivacaine 0.5% on somatosensory evoked potentials (SEP) to electrical stimulation of the posterior tibial nerve was examined in six patients. Epidural analgesia significantly increased onset time and latencies of the early components in SEP, while the amplitudes decreased. These results suggest that SEP may be valuable in the objective evaluation of possible differential neural effects of local anaesthetic agents following epidural or intrathecal administration.