Monitoring technique affects measurement of recovery from succinylcholine

To compare recovery time from neuromuscular blockade after the administration of a single intravenous bolus of succinylcholine (1 mg/kg), we measured, both mechanically and electromyographically, the evoked twitch responses in the hand muscles of 10 patients. Electromyographic data were obtained, electronically integrated, and recorded by a newly available clinical monitoring device. Using both the mechanical and the electromyographic devices, we recorded the times for first return of twitch, as well as for 25% and 75% recovery of twitch height compared with prerelaxant twitch baseline values and compared the values by calculating least-squares regression lines. Times given by the electromyographic device for these measures of returning neuromuscular function were notably longer than those given by the mechanical evoked force monitor. No such findings have been reported in previous studies that compared these two techniques for monitoring of muscle recovery from nondepolarizing relaxants. The specific reasons for the differences found in this study are unknown.