[Mechanomyography and electromyography--2 competing methods of relaxometry using vecuronium]

The recording of the evoked twitch tension has been the established reference method to quantitate neuromuscular blockade. The evoked compound electromyogram has been introduced later as a clinically more convenient alternative. We compared both methods in 20 patients in whom cumulative dose response curves of vecuronium and the time constants of weaning neuromuscular blockade were determined. The evoked twitch tension was slightly more sensitive in detecting residual neuromuscular blockade than the EMG. No significant differences between the two methods were found in the cumulative 90% blocking dose, the duration of block and the recovery time (25%-75%). These results are in agreement with communications of previous authors using different nondepolarizing muscle relaxants. In the absence of abnormal conditions such as neuromuscular disorders and hypothermia, recording of evoked electromyography is a clinically satisfactory method to quantitate neuromuscular blockade.