We constructed a single-dose response curve for succinylcholine in 30 obese adolescents during thiopental-fentanyl anesthesia administration by using 100 microg/kg, 150 microg/kg, or 250 microg/kg IV. The maximal response (percent depression of neuromuscular function) of the adductor pollicis to supramaximal train-of-four stimuli was recorded by using a Datex (Helsinki, Finland) relaxograph. Linear regression and inverse prediction were used to determine doses of succinylcholine to produce 50% (ED(50)), 90% (ED(90)), and 95% (ED(95)) depression of neuromuscular function. The ED(50), ED(90), and ED(95) were 152.8 microg/kg (95% confidence interval: 77.8-299.5), 275.4 microg/kg (95% confidence interval: 142-545.7), and 344.3 microg/kg (95% confidence interval: 175.3-675. 3), respectively. This ED(50) is similar to the dose reported for similarly aged, nonobese adolescents, 147 microg/kg. The previously reported ED(95) for succinylcholine in nonobese adolescents, 270 microg/kg, is within the 95% confidence interval generated for ED(95) in our study.
Implications: The potency estimates for succinylcholine in obese (body mass index > 30 kg/m(2)) adolescents are comparable to those in similarly aged nonobese adolescents when dosing is calculated based on total body mass and not lean body mass. When a rapid sequence induction of anesthesia is considered in an obese adolescent, the dose of succinylcholine should be based on actual (not lean) body mass.