Dose-response curves for succinylcholine: single versus cumulative techniques

This study was performed to determine the potency of succinylcholine using the single-dose technique, and to test the ability of the cumulative dose technique for generating dose-response data. Thirty-eight adult patients received single doses (n = 18), cumulative doses (n = 10), or cumulative doses of succinylcholine with an infusion to replace metabolized drug (n = 10). During opiate-thiopental-nitrous oxide anesthesia the force of contraction of the adductor pollicis in response to train-of-four stimulation was measured and recorded. Linear regressions were obtained between the logit transformation of neuromuscular blockade and log dose. Similar potencies were obtained with single dose and cumulative dose with infusion techniques with an ED90 of 0.27 +/- 0.03 and 0.26 +/- 0.02 mg/kg (mean +/- SEM) respectively. However, cumulative dose without infusion significantly underestimated potency with an ED90 of 0.42 +/- 0.06 mg/kg (P less than 0.05 compared with the other two techniques). It is concluded that cumulative dose techniques can be accurately employed to determine the potency of succinylcholine if an infusion is utilized to compensate for eliminated drug. The data suggest that clinically used doses of succinylcholine (1.0-1.5 mg/kg) are equivalent to 3-5 times the ED90 and may explain the excellent intubating conditions provided by this drug.