Evidence-based practice and neuromuscular monitoring.

OVER the last years, a growing body of information has accumulated in the anesthesia literature about the advantages and pitfalls of various techniques used for quantitatively monitoring neuromuscular function in routine anesthetic practice and the associated incidence (and consequences) of residual neuromuscular block in the postoperative period. Many methods are available, ranging from quantitative strain–gauge techniques, electromyography, acceleromyography, phonomyography, etc. However, quantitative techniques are not widely used, with most anesthesiologists relying on visual or tactile assessment of the train-of-four (TOF) ratio, or, in many cases, no neuromuscular monitoring at all. One argument for such qualitative approaches to monitoring is that with modern short and intermediate acting relaxants, residual paralysis is not a clinical problem or, even if patients are not completely reversed by the end of the case, the block will dissipate in a few minutes. Another approach is “reverse everyone,” which is viewed by some as uniformly easy, safe, and effective for patients given these agents. There is now increasing evidence that this relaxed attitude to neuromuscular monitoring is unwise. The study by Debaene et al., published in this issue of ANESTHESIOLOGY, has a clear message to all of us. The authors examined the incidence and magnitude of a neuromuscular block on arrival in the PACU in a large group of relatively unselected patients who had received a single dose of intermediate-duration relaxant for intubation (rocuronium, vecuronium, or atracurium). Patients received no other relaxant during their surgery and did not receive reversal agents at any time. The message is that, while it may be presumed that the attending anesthesiologists felt that adequate neuromuscular function was present at the time of transfer, 45% of the patients arrived in the recovery room with a residual neuromuscular block, defined as an adductor pollicis TOF ratio of less than 0.90! Sixteen percent had a TOF ratio of less than 0.7. Interestingly, in sufficiently cooperative patients, even clinical tests were frequently abnormal; 15% of tested patients failed a test of head lift. Even in patients tested more than 2 h after drug administration, the incidences of residual paralysis were 10 and 37% (based on a TOF ratio of less than 0.7 or less than 0.9, respectively). The specific relaxant used did not influence these incidences. The study was not a rigorous study of drug kinetics or twitch depression and recovery. Instead, the authors examined something close to routine clinical practice; that is, the anesthesiologist was free to select the neuromuscular blocking drug, the dose, and whether to use or not use neuromuscular monitoring. There are clearly experimental problems with this approach, and it is unfortunate that the authors did not provide further information about the actual anesthetic practice (in particular whether or not some form of monitoring was used). This limits the external validity of the study. Nevertheless, the results clearly demonstrate that a disturbingly high fraction of patients did not have adequate neuromuscular function on arrival in the recovery room. Recently, several studies focusing on this kind of broad, unselected patient population have been published. They all found an alarmingly high incidence of residual paralysis in the recovery room despite the use of intermediate acting neuromuscular blocking agents (vecuronium, rocuronium, atracurium, and cisatracurium). There are several possible explanations for this unexpectedly high incidence. One reason might be the change in definition of clinically significant residual paralysis from a TOF ratio of 0.70 to 0.90. However, since clinical measures are also commonly abnormal, this cannot be a complete explanation. Thus, it is clear that the widespread belief that intermediate-acting muscle relaxants have a very low tendency to cause residual paralysis (and therefore, that it is not necessary to monitor or even to reverse the neuromuscular block) is very wrong. Combining the results of the current study with the results from several similar investigations, there is now sufficient information to support a general change in the attitude towards monitoring and reversal of a neuromuscular block in routine anesthetic practice. Though anesthesiologists probably have a relatively low threshold for carrying new monitoring equipment into the operating room (e.g., BIS, AEP, ST-analysis, endtidal anesthetic gas concentrations, etc.), few techniques have been documented to affect patient outcome. In this This Editorial View accompanies the following article: Debaene B, Plaud B, Dilly M.-P., Donati F. Residual paralysis in the PACU after a single intubating dose of nondepolarizing muscle relaxant with an intermediate duration of action. ANESTHESIOLOGY 2003; 98:1042–8.