[Neurologic sequelae of spinal anesthesia: local anesthetic toxicity]

Recent reports of cauda equina syndrome following continuous spinal anesthesia have generated concern regarding the safety of not only this particular technique but also of the local anesthetic agent itself. This concern has been reinforced by data suggesting that similar injuries have occurred with repeated injection after a "failed spinal", and by reports of transient radicular irritation following single subarachnoid injection. This paper summarizes the above cases and reviews recent experiments performed to determine the mechanisms underlying local anesthetic toxicity and the factors that contribute to injury. These experiments suggest that the recent injuries resulted from a direct effect of the local anesthetic and that anesthetic-induced impairment does not result from blockade of the sodium channel, per se. These experiments also suggest that development of a safer anesthetic is a realistic goal.