To the Editor:
We read with interest the article by Bulka et al.1 regarding the relationship between the management of intraoperative neuromuscular blockade and postoperative pneumonia. The use of large databases to address rare outcomes has increased in recent years. The value in using these databases is the large number of patients who can be assessed. Such large numbers would be extremely challenging to achieve in a randomized controlled study. However, a major limitation and concern with database studies like this one is subsequent confusion between correlation and causation. With regard to residual paralysis, we believe that these challenges can be bypassed with one simple technique—the objective monitoring of the effects of a neuromuscular blocking agent. Although the incidence of residual neuromuscular blockade at extubation is significant,2 currently, monitoring of neuromuscular blockade is still not an explicitly articulated American Society of Anesthesiologists basic monitoring standard.3 Whereas many practitioners use such monitoring in their practice, others rely on clinical signs of strength or other outdated measures, such as the 5-s head lift or 50-Hz sustained tetanus to determine adequate recovery from neuromuscular blockade before extubation. Still others simply rely on time from reversal agents being given.4
Perhaps the reluctance to consistently monitor the effects of neuromuscular blocking agent and, most importantly, the adequacy of recovery before extubation, represents a peculiar psychologic phenomenon. The practice of anesthesiology is replete with situations in which parameters are monitored at baseline and for the effects of any intervention. In addition, many of our routine practices could be deemed unnecessary in the majority of patients, yet are performed to prevent devastating outcomes in the remaining small percentage of patients. Examples include preoxygenation before the induction of anesthesia, maintenance of blood pressure within certain parameters to prevent stroke or myocardial ischemia, and maintenance of normothermia to prevent wound infection and cardiovascular complications. These practices have become routine or standard because they protect patients from rare but serious complications. As Perrow5 points out, Murphy’s law is wrong: everything that can go wrong usually goes right, and then we draw the wrong conclusion. The ability to adequately ventilate 1,000 successive patients could lead one to disregard the need for preoxygenation, but this would lead to the trap that Perrow5 warns against. Similarly, we believe that the low frequency of complications from residual paralysis (reintubation, respiratory distress, and pneumonia) leads to a sense of complacency, because we either do not see or do not recognize these complications, especially if, as with pneumonia, they manifest later. Finally, when we see something rarely, it is easy to equate low risk with no risk, to the point that when the adverse outcome does occur, we are convinced it must be from some other cause. However, when common causes are ruled out, uncommon causes become very likely. Although twitch monitors are not without their own limitations, we believe the routine confirmation of adequate strength before extubation, using a quantitative train-of-four ratio greater than 0.9 or sustained 5-s tetanus at 100 Hz, can reduce the risk of adverse events from residual neuromuscular blockade and should become a standard of care.
The authors declare no competing interests.