Comparative performance of stimpod electromyography with mechanomyography for quantitative neuromuscular blockade monitoring

Purpose The purpose of this study was to compare the Stimpod electromyograph neuromuscular blockade monitor to mechanomyography, which is widely considered to be the reference standard. Methods The Stimpod electromyograph was used with its designated electrode array on the same hand as the mechanomyograph. Pairs of train-of-four measurements were recorded every 0.5-2 min. When the train-of-four count was zero on the electromyograph monitor, pairs of post tetanic count measurements were recorded every 2.5 min, instead of train-of-four measurements. Measurements were recorded from immediately after induction of anesthesia until just before emergence. Stimulation current was set to 60 mA with a duration of 200 microsec. The mechanomyography recording system recorded each twitch waveform for analysis. High resolution electromyograph waveforms were also recorded using a datalogger accessory provided by the manufacturer, facilitating inspection of individual waveforms. The administration of neuromuscular blocking drugs was left up to the discretion of the anesthesia care team. Results Twenty-three patients contributed 1,088 data pairs suitable for analysis. Bland-Altman analysis of 415 pairs of train-of-four ratios showed a bias of 0.028 and limits of agreement of -0.18 and 0.24. Two hundred seventy-three train-of-four count data pairs were compared by Cohen’s quadratically weighted kappa which was calculated to be 0.44, indicating moderate agreement. Three hundred thirty-eight post tetanic count data pairs were compared by Cohen’s quadradically weighted kappa which was calculated to be 0.80, indicating substantial agreement. Conclusion The electromyograph produced results that were comparable to the mechanomyograph.