Succinylcholine Sensitivity in Cerebral Palsy

Abstract

In Response: We appreciate the comments by Drs. Antognini and Gronert regarding regulation of acetylcholine receptors and altered sensitivity to agonist and antagonist neuromuscular blockers. We agree that our observations may raise two issues which should not be confused. There appears to be inconsistency between our finding of minimal increase in sensitivity of succinylcholine and the marked resistance to nondepolarizers noted by others in children with cerebral palsy by Moorthy et al. [1]. Perhaps the resistance noted by Moorthy et al. was due more to the effects of anticonvulsants [2] than to the presence of cerebral palsy. Indeed, Melton et al. [3] find prolongation of the effect of succinylcholine in adults without neuromuscular disease who had been receiving anticonvulsants for more than 1 mo. Altered response to agonists or antagonists in the presence of chronic anticonvulsant use could be due to mild up-regulation of acetylcholine receptors. However, in patients with cerebral palsy who are not receiving chronic anticonvulsant therapy, one might hypothesize that the chronic and repeated spasms these patients exhibit may play a role in acetylcholine receptor regulation. The slight difference in the ED50 of succinylcholine we noted suggests that there was not as much alteration of neuromuscular function in our patients with cerebral palsy as has been noted in patients receiving anticonvulsants. Our findings with regard to the altered potency of succinylcholine are not of large enough magnitude to be construed as support for the claim that acetylcholine receptors are up-regulated in children with cerebral palsy. We agree that a definitive explanation of the mechanism underlying these observations awaits studies of a different nature. Mary C. Theroux, MD Departments of Anesthesiology, Alfred I. duPont Institute, Thomas Jefferson University Hospital, Wilmington, DE 19899 Barbara W. Brandom, MD Department of Anesthesiology, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213