Succinylcholine neuromuscular blockade in subjects homozygous for atypical plasma cholinesterase

Abstract

Type, duration, and treatment of neuromuscular blockade following 1 mg/kg succinylcholine were studied on 16 occasions in 12 patients homozygous for atypical plasma cholinesterase during halothane-nitrous oxide-oxygen anesthesia using train-of-four (TOF) nerve stimulation. They were divided into four groups. In two cases the spontaneous recovery of the succinylcholine block was followed. In five cases the block was treated by intravenous injection of human cholinesterase (Cholase®, 90-270 mg) 30 min after succinylcholine. In five cases Cholase (90-270 mg) was injected 90 min after succinylcholine. In the remaining four cases cholinesterase inhibitors were given either alone (one case) or in combination with Cholase (three cases) 90 min after succinylcholine. It was found that spontaneous resolution of the neuromuscular block had four phases: phase A (30-50 min: complete neuromuscular block; phase B (20-25 min): relatively rapid increase in both twitch height and TOF ratio; phase C (20-30 min): a plateau phase; phase D (90-120 min): a slow increase in TOF and, in the final part of this phase, an increase in twitch height as well. There was a pronounced fade of the TOF response in all patients in phases B, C, and D. Cholase 30 min after succinylcholine improved neuromuscular transmission impressively within 5-10 min. After 90 min Cholase had a much less pronounced effect. However, at this time the block could be completely reversed by a combination of Cholase and a cholinesterase inhibitor. The different results at 30 and 90 min presumably result from a change of the character of the block from a depolarizing to a desensitizing one (phase II block). Accordingly, rational treatment of such a block should include human cholinesterase for the depolarizing part of the block and a cholinesterase inhibitor for the desensitizing part of the block.