Reaction to succinylcholine in two patients segregating for the plasma cholinesterase allele E^k

Abstract

Recently, several new alleles have been identified at plasma cholinesterase locus E1. We have had the opportunity for the first time to monitor the response to succinylcholine in two patients with the newly discovered genotype Ea1Ek1. The duration of action and type of neuromuscular block following succinylcholine 1.0 and 1.5 mg kg-1 i.v., respectively, were evaluated using train-of-four nerve stimulation and a Myograph 2000. One patient was anaesthetized with halothane, and the other was given a modified neurolept anaesthesia. Time to first response to nerve stimulation was 15 and 16 min, and time to 50% twitch height recovery was 19 and 20 min, respectively in the two patients. Both showed a depolarizing block. One of the patients received three bolus doses of succinylcholine 1 mg kg-1. This patient gradually developed a phase II block, which was easily reversed by edrophonium. The results indicate that patients with genotype Ea1Ek1 are slightly more sensitive to succinylcholine than are genotypically normal patients (Eu1Eu1) and patients heterozygous for the normal and the atypical gene (Eu1Ea1).

Rapid simultaneous genotyping of the frequent butyrylcholinesterase variants Asp70Gly and Ala539Thr with fluorescent hybridization probes

“…Furthermore, the K-variant is linked to 89% of the A-variant alleles [8]. However, patients found to be compound heterozygous for the A-and Kvariants seem to be more sensitive to succinylcholine than are the phenotypically normal patients and patients heterozygous for the A-variant [13]. Yet the clinical importance of the K-variant without linkage to the A-variant has not been studied.…”

“…The results were equivocal in another 25% of patients who were potential carriers of the A-and/or the K-variant [7]. Using biochemical assays, the K-variant can only be identi® ed using a speci® c inhibitor, the Ro-Number [12], and only when the A-variant allele is also segregating in the family [13]. Both variants may cause prolonged response to succinylcholine and mivacurium, but, clinically, the A-variant is the most important BChE variant in anaesthesia.…”

Plasma cholinesterase and abnormal reaction to succinylcholine: twenty years' experience with the Danish Cholinesterase Research Unit

“…Five patients heterozygous for the atypical and the K variant showed a slightly prolonged duration of action compared to patients with genotype LA. All patients showed a depolarizing block following the initial bolus dose of succinylcholine (23). The patient heterozygous for the atypical and the Hvariant ( Table 3) represents the first patient ever with this genotype to have the response to succinylcholinc recorded.…”

“…In patients hetcrozygous for one or two abnormal genes, repeated doses of succinylcholine often cause a phase I1 block and a prolonged response (21,23).…”