relationship between succinylcholineinduced apnea and dibucaine number in patients with genetic deficiency of plasma cholinesterase

in this study, a commercially available kit in which propionylthiocholine is used as a substrate and a dibucaine solution to determine the variants of the enzyme were utilized. plasma cholinesterase activity of 151 patients who underwent different operations was measured during a period of six months. the mean±sd of the enzyme activity in 150 patients was 4.39±1.17 ku/l .. seventeen patients (11.2%) were found to have a serum cholinesterase activity of less th'an normal «3 ku/l), but the period of apnea and the dibucaine number (dn) were found to be normal. eight patients (5.3%) displayed an increased sensitivity to succinylcholine. six of these patients (4%) were heterozygous for atypical enzyme with a mean period of apnea of 18.6 min (range 12-35 minutes) and had a dibucaine number of less than normal (‹80%). the dn of the other two patients (1.3%) who were homozygotes and had an exceedingly low atypical enzyme allele was 10% and 24%. the mean±sd dn value, in the 149 out of 151 patients was 84.41±2.91 %, and the dn ranged from 10-90% in these patients. the mean±sd apnea period in the 149 patients was 6.37±4.28 min.