Neuromuscular Monitoring: Keep It Simple!

Abstract

See Article, p The principles of logic … are true, simply because we never allow them to be anything else. —Sir Alfred Jules Ayer (October 1910–June 1989) The proposals by Biro et al,1 which appear in this month’s “Open Mind,” address the future of perioperative neuromuscular monitoring. In essence, their article is an “opinion piece,” which clearly was well received by the peer-review experts of this Journal. However, the authors of this editorial are not ready to accept all of the suggestions by Biro et al.1 What follows is a contrarian response that we readily admit expresses our own personal biases. The first half of the article by Biro et al1 consists of proposed modifications of Naguib et al2 as to how to define depth of neuromuscular block. What does “deep” or “moderate” block actually mean? The authors’ suggestions are not unreasonable, although it is difficult to see how they will be helpful to the clinical anesthesiologist. Intraoperative decisions regarding drug dosage should ultimately be based on the evoked train-of-four ratio or the posttetanic count, not on how we define these levels. The potential benefit of labeling each level is that investigators doing comparative studies between the relationship of depth of block and the adequacy of surgical operating conditions will be more likely to equate similar degrees of depth of relaxation. In the latter setting, we would suggest a further modification (Table) as we believe that train-of-four counts of 1 and 3 should not be grouped together because they represent sufficiently different levels of blockade.Table.: Levels of Neuromuscular BlockBiro et al1 argue for the need for deep neuromuscular blockade in different surgical procedures. From our perspective,3,4 we have no issues regarding the use of deep neuromuscular block when it is indicated, as in, for example, neurosurgical, ophthalmological, airway, and occasionally laparoscopic surgeries. However, we still maintain our views regarding the lack of evidence that supports the routine use of deep block in laparoscopic and robotic-assisted procedures.5,6 We agree that the use of neostigmine to reverse deep neuromuscular block will not be effective and will not result in adequate recovery, but we question the authors’ suggestion that it may result in recurarization in this scenario.7,8 The majority of reported cases of recurarization after neostigmine are very poorly documented. Most, if not all, represent inadequate antagonism and subsequent fatigue rather than recurrence of block. Recurarization, as a phenomenon, may be seen clinically after using inadequate doses of sugammadex.9,10 The more controversial aspect of the article by Biro et al,1 we think, relates to the mandated features that they suggest should be incorporated into future quantitative (objective) neuromuscular monitors. We cannot agree with the statement that the stimulation patterns such as those available on the TetraGraph (Senzime B.V., Uppsala, Sweden), TwitchView (Blink Device Company, Seattle, WA), or TOFScan (IDMED, Marseille, France) are “still not sufficient.” Quantitative monitors need to be able to display the posttetanic count and train-of-four count/ratio in real time. Available units and those on the immediate horizon already do this. The authors argue for much more elaborate capabilities: “Modern neuromuscular monitors should have a built-in trend function that can be reviewed by the clinician contemporaneously, and should have the ability to be annotated by the user. We would welcome equipment with implemented algorithms that [automatically] modify both the stimulation pattern and the interval time according to the result of the last measurement.” One common complaint that we hear from clinicians regarding quantitative neuromuscular monitors is that the user interface is not user friendly. We are unconvinced that adding automatic modes and graphic displays to small hand-held devices would represent a step forward. We are strong propon