suxamethonium Flashcards
Dibucaine number
-Neuromuscular block induced by succinylcholine or mivacurium can be significantly prolonged if the patient has an abnormal genetic variant of butyrylcholinesterase
-Analysis of butyrylcholinesterase involves the determination of both enzyme activity and biochemical phenotypes. Phenotype is determined by the use of specific enzyme inhibitors (such as dibucaine or fluoride) that produce phenotype-specific patterns of dibucaine or fluoride numbers (Table 12.2). Molecular genetic analyses can determine the true genotypes.
-Type of a
butyrylcholinesterase- Genotype -Incidence number-
Response to succinylcholine or mivacurium
-Homozygous typical -E1uE1u -Normal -70-80 Normal
-Heterozygous atypical E1uE1a 1/480 50-60 Lengthened by 50%-100%
-Homozygous atypical E1aE1a 1/3,200 20-30 Prolonged to 4-8 hours
-Dibucaine, a local anesthetic with an amide linkage, inhibits the activity of normal butyrylcholinesterase by more than 70%, compared with only approximately 20% inhibition of the activity of atypical enzyme
-It is important to recognize that the dibucaine number reflects quality of cholinesterase enzyme (ability to hydrolyze succinylcholine) and not the quantity of the enzyme that is circulating in the plasma.
-The longest period of apnea after the administration of succinylcholine was found in patients homozygous for the silent gene (E1sE1s).
-Although the dibucaine or fluoride number indicates the genetic makeup of an individual with respect to butyrylcholinesterase, it does not measure the concentration of the enzyme in the plasma, nor does it indicate the efficiency of the enzyme in hydrolyzing succinylcholine or mivacurium.
