We thank Dr. Bowdle et al. for their interest in our article showing how quantitative monitoring can be incorporated into clinical practice. We fear they may have missed the major lesson of this work, however, which was modifying clinician behavior so that the vast majority of our patients benefitted from quantitative monitoring of neuromuscular blockade.
Bowdle et al. assert that we used acceleromyography only to save money, at the cost of patient safety, and that we claimed device technologies were interchangeable. To the contrary, our primary focus has always been patient safety, and we discussed technology differences multiple times in our article. In our methods and discussion, we recommended acceleromyography ratio greater than1.0 and further explicitly stated that acceleromyography ratios 0.9 to 1.0 may represent incomplete reversal. Supplemental Digital Content figure 2 stated that the acceleromyography train-of-four ratio goal should be greater than 1. We recognized the differences. Bowdle et al. discount acceleromyography technology on the basis of baseline train-of-four ratios. A better approach may be to look at studies measuring the train-of-four ratio measurement biases for the two technologies compared to the reference standard, mechanomyography. The mechanomyography–electromyography train-of-four bias has been reported as 4.7%, suggesting that electromyography overestimates the train-of-four ratio by about 0.04 compared to mechanomyography. The mechanomyography-acceleromyography train-of-four biases range from –8.1 to 9.8%, suggesting that acceleromyography may overestimate the train-of-four ratio by as much as 0.09 compared to mechanomyography. Both technologies overestimate train-of-four ratios compared to the reference standard according to the research. Insight about these technologies can also be found in 25 studies from 1992 to 2018 that documented many patient benefits associated with recovery from neuromuscular blockade, including improved swallowing, pharyngeal function, airway patency, vision, speech, muscle strength, breathing mechanics, and airway patency. Thirteen of these studies used nonnormalized acceleromyography of which 9 studies cited 0.9 as the train-of-four ratio cutoff for improved patient outcomes. We still believe in attaining an acceleromyography ratio greater than 1, although this evidence suggests it may not be necessary. In our professional practice change, we set the train-of-four ratio goal at 0.9 despite our mixed practice of electromyography and acceleromyography for simplicity in messaging. Additionally, our anesthesia records do not specify the type of quantitative monitor used, eliminating our ability to parse out our patient data based on the technology used. However, table 3 reflected our practice of using acceleromyography with a target train-of-four ratio greater than 1, which showed that postimplementation average train-of-four ratios were greater than 1 for all reversal groups. In summary, we chose to use acceleromyography not just to save $20 to $25 per patient (cost of proprietary electromyography sensor array), but, more importantly, because it is a well-studied, reliable way to monitor neuromuscular function.
Bowdle et al. question the validity of our findings due to manual data entry by our physicians and Certified Registered Nurse Anesthetists. Research staff data collection represents a more robust study design, but it is simply unattainable in a process improvement project involving all patients given a nondepolarizing neuromuscular blocker (24 hours/day, 7 days/week, 365 days/year). We would have preferred automatic electronic data entry, which we stated in our article. The suggestion by Bowdle et al. that our providers falsified train-of-four ratios, however, would not be entirely addressed by electronic data entry because manual override would be possible.
Bowdle et al. advocate for subjective tactile twitch counting. Our practice uses quantitative monitoring.
Bowdle et al. claim that TwitchView array failures are rare, citing controlled observational studies. It appears we cannot reproduce this level of reliability in our clinical practice. Our article describes a real-life application of two technologies present and functional for use by all providers. There is enthusiasm for both technologies at our institution, but our providers consistently report more TwitchView equipment failures. An observation of 100 consecutive uses of the TwitchView by Dr. Michael Todd, M.D. (University of Minnesota School of Medicine, Minneapolis, Minnesota; written communication, August 12 and 16, 2022) demonstrated 84% success without corrective measures, 10% success after corrective maneuvers, and 6% failure rate due either to device or cable problems, electrode failures, or uncorrectable electrode dislodgement. These data come from an experienced provider who observed that skin preparation and reinforced array taping (including application of benzoin) increased success rates. In our article, we reported the experiences of our providers that may be improved with meticulous application and troubleshooting of the TwitchView equipment.
Understanding the equipment used in anesthesia care is important. We believe there is more than one acceptable technology to attain quantitative neuromuscular measurements. We recognize there are idiosyncrasies of acceleromyography technology. However, acceleromyography is an accepted and useful method for monitoring neuromuscular blockade, especially when the hand is accessible. We appreciate the excellent functionality of the TwitchView and Stimpod and will continue using both devices.
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