Automated determination of cholinesterase activity in plasma and erythrocytes by flow-injection analysis, and application to identify subjects sensitive to succinylcholine.

This automated spectrophotometric method for determination of cholinesterase activity in erythrocytes and plasma is based on measurement of the choline produced at 30 degrees C by the hydrolysis of acetyl-, butyryl-, or succinylcholine. Blanks, standards, and samples are prepared by a Gilson robotic unit. Use of flow-injection analysis for detection allows use of smaller volumes of reagent and sample. We applied this method to the study of 91 healthy subjects and members of two families with succinylcholine sensitivity. Results with use of the three different substrates for determination of activity in plasma correlated well (r greater than 0.94). Results for plasma and erythrocytes from healthy subjects are lower in women less than 50 years old than in women greater than 50 years or men. Values for plasma obtained with succinylcholine substrate (range: 31 to 100 U/L) allow detection of very sensitive subjects--AA phenotypes (less than 10 U/L)--but do not distinguish the UA from the UU phenotype.