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Evidence-Based Management of Neuromuscular Block

Viby-Mogensen, Jørgen, MD, DMSc, FRCA*; Claudius, Casper, MD, PhD

doi: 10.1213/ANE.0b013e3181e1d94c
Editorials: Editorials
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From the *Department of Anaesthesia and Intensive Care, Copenhagen University Hospital, Rigshospitalet, Denmark; and the Department of Anaesthesia, Hillerød Hospital, Denmark.

Funding: None.

Conflicts of interest: Both authors have received research funds and functioned as ad hoc consultants for several companies, including Organon and Schering Plough Pharmaceuticals, the manufacturer of the TOF–Watch monitor mentioned in this article.

Address correspondence to Jørgen Viby-Mogensen, Sømarksvej 3, 2900 Hellerup, Denmark. Address e-mail to Viby@dadlnet.dk.

Accepted April 7, 2010

“Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research.”1

The three articles in this issue of the journal dealing with postoperative residual block24 allow us the possibility of answering the question, “Do we, the anesthesiologists in the United States (U.S.) and the European Union, practice evidence-based management of neuromuscular block, and if not, why not?” On the basis of the results of the three articles, the short answer to the question is, “No, and we still do not know why. We can only speculate.”

For most of us who have been doing research and teaching in this area for many years, the results of the three studies, and thus the short answer to the question above, do not come as a big surprise. However, this does not detract from the quality and value of the three articles. The authors are to be congratulated for doing a very good job. The articles by Murphy and Brull nicely document the available evidence on definitions, incidence, significance, and methods available for reducing the risk of potentially clinically significant postoperative residual block (train-of-four [TOF] ratio <0.90).2,3 The third article by Naguib et al.4 presents an interesting survey of the current management of neuromuscular block in the U.S. and in Europe.

On the basis of the available evidence, Brull and Murphy conclude that “perioperative monitoring of evoked neuromuscular responses that guides the administration of anticholinesterases and documents return of neuromuscular function should be a standard of care.”3 Though we could not agree more, this statement is quite controversial, not least in the U.S., and it will probably generate objections and discussion. There has been an unofficial “transatlantic debate” going on for several years among neuromuscular experts. Basically, European experts have advocated that objective neuromuscular monitoring should be a standard of care, whereas at least some experts from the U.S. have been more reluctant to accept this. The argument against is that it has never been convincingly documented that intraoperative neuromuscular monitoring actually decreases the incidence of residual paralysis.3,5,6 Some of this disagreement may be caused by confusion between the two words intraoperative and perioperative. Intraoperative, strictly speaking, includes only the time of the operation itself. The perioperative period includes the time before, during, and immediately after the surgery, before the patient is transferred to the postoperative care unit. It is correct that there is no convincing evidence in the literature that intraoperative monitoring of neuromuscular function, whether subjective (visual or tactile evaluation of the response to nerve stimulation) or objective (mechanomyography, acceleromyography, kinemyography, or electromyography), decreases the incidence of potentially clinically significant postoperative residual paralysis.3,5,6 However, monitoring does obviously make the evaluation and the management of the neuromuscular block during the operation easier. In this respect it is not critical whether the clinician is using subjective or objective monitoring. The level of block can easily be quantified by tactile evaluation of the response to posttetanic count stimulation for intense and deep block, and TOF stimulation for moderate block.7 In contrast, during the recovery phase of the neuromuscular block, it is not possible with certainty to quantify the degree of block manually or visually when the TOF ratio is >0.40.3 Therefore, it is not possible by subjective monitoring to exclude potentially clinically significant postoperative residual paralysis (TOF ratio <0.90). Thus, it cannot come as a surprise that the use of perioperative subjective monitoring does not significantly decrease the incidence of postoperative residual block. Neither by the use of intermediate-acting drugs, clinical tests, routine reversal, subjective monitoring, or a combination of these methods is it possible with certainty to exclude potentially clinically significant postoperative paralysis, defined as a TOF <0.90.3,811 Contrary to the above, there is good evidence that objective monitoring performed perioperatively, including the recovery phase of neuromuscular block,7 significantly decreases the incidence of postoperative residual paralysis.8,9,1113 This is in accordance with the evidence that the only way to ensure a TOF >0.90 is by objective monitoring.3

An argument often heard against routine perioperative objective monitoring of neuromuscular function is that though it has been documented in a randomized controlled clinical trial that postoperative residual paralysis (TOF ratio <0.70) is a risk factor for development of postoperative pulmonary complications when using the long-acting drug pancuronium, the same study did not find such a relationship with the intermediate-acting drugs (atracurium and vecuronium).10 However, Murphy and Brull nicely review the literature on adverse effects of residual neuromuscular block.2 They document that there is evidence that postoperative paralysis caused by intermediate-acting drugs may cause upper-airway obstruction during transportation to—and hypoxemia, delayed discharge, and critical respiratory events in—the postoperative care unit.2 With this knowledge in mind, it is hard to understand the resistance against routine perioperative objective monitoring when using these drugs. Could it be that sometimes our preconceived opinions and attitudes influence the way we perceive evidence, more than the evidence influences our opinions and attitudes? Also, one should remember that absence of evidence or insufficient evidence for an effect or a relationship does not necessarily indicate that there is no effect or no relationship. Evidence may be lacking simply because there are insufficient studies or because of inadequate design in the studies actually performed.

As is mentioned by Brull and Murphy,3 there are important limitations to the devices currently commercially available. Most of the monitors are too cumbersome to use, it takes a relatively long time to achieve a reliable response, they are very sensitive to external disturbances, the results are often not easy to interpret, and training and routine use is necessary. Furthermore, the free-standing monitors with their cables and many parts are too fragile, and some of them break into pieces too easily. So, though we wholeheartedly agree with Naguib et al.4 that formal training programs and official guidelines on best practices for perioperative monitoring should be developed by professional organizations, to really change anesthesiologists' attitudes to objective neuromuscular monitoring, the monitors have to be improved. First, the monitors should be a part of the anesthetic machine; they should be reliable, easy, and fast to apply during preparation of the patient for anesthesia, preferably in one piece with one connecting cable to the built-in monitoring unit; and the display on the screen should be very simple and easy to read and understand. Then and only then can we hope to influence the attitudes of our fellow colleagues.

In Europe, contrary to what many people had expected, we have experienced an increased interest in teaching and training in objective neuromuscular monitoring after the introduction of sugammadex, a trend also observed by the manufacturer of one of the commercially available neuromuscular monitors (the TOF–Watch). Therefore, more than ever we see an opportunity to change practices, if and when we get better and easier-to-routinely-use objective neuromuscular monitors and have standards and guidelines developed by professional organizations. But most important, there is a significant educational task ahead for those responsible for specialist training, postgraduate education, and continuing medical education.

On the basis of the evidence presented in the three articles,24 we would like to present what we consider the key points of the three articles:

  1. Potentially clinically significant postoperative residual paralysis is a clinical problem and may pose a threat to the health of the patient.
  2. It is not possible by any clinical test or combinations hereof, nor by tactile or visual evaluation of the response to TOF, tetanic (50 or 100 HZ), or double-burst stimulation, to exclude with certainty potentially clinically relevant postoperative residual paralysis.
  3. Good evidence-based practice dictates that the anesthesiologist, preferably perioperatively but at least before sending the patients to the recovery ward, should ensure that the TOF ratio is 0.90 or more by using an objective monitor.
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REFERENCES

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