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LETTER TO THE EDITOR

Time to Dispose of Nondisposable LMAs

Department of Anaesthesia and Intensive Care; James Cook University; Cairns Base Hospital; Cairns, Australia; jbrimaco{at}bigpond.net.au (Brimacombe, Laupu) Department of Anaesthesia and Intensive Care Medicine; Leopold-Franzens University; Innsbruck, Austria (Keller)

In Response:

We thank Dr. Walsh for his interest in our study. The potential for prion transmission via reusable LMA devices is indeed a matter of great importance; however, any mandate to dispose of nondisposable LMA devices must be evidence- and/or logic-based, rather than driven by fears of the unknown, possible adverse public opinion, and scientific misinformation. We will respond to each comment in turn.

First, Dr. Walsh presents us with a classic example of scientific misinformation when he states that "even when they used a solution of potassium permanganate beforehand, the residual area of staining was still 20%." In fact, we showed that 20% of LMAs were contaminated and that the average area of contamination was 2.5%, and estimated that potassium permanganate removes 91% of residual protein. Rather than showing that nothing can be done to remove protein deposits, we showed that much of it can be removed.

Second, it is not true that the least accessible parts are more prone to protein contamination, as exposure to contaminants and the conditions that make them stick may also be reduced. A study of ProSeal LMAs showed that the finger strap area, which is not easily accessible, had no staining (1). There is evidence that protein contamination is more likely in those areas in contact with pharyngeal tissues (2). Thus the least accessible parts possibly pose a lower risk.

Third, Dr. Walsh states that prion proteins and other pathogens may be transmitted by reusable LMAs. Yet, there are no reports of direct transmission of pathogens despite as many as 150 million LMA uses worldwide (3). Indirect transmission of hepatitis C has been reported with the LMA, but was related to cross-infection from a contaminated circuit (4) and could have occurred with a disposable LMA.

Fourth, we never stated that there were no alternatives to reusable LMAs, but rather pointed out that the disposable LMAs were relatively clinically unproven. This issue is pivotal in determining the safety of reusable versus disposable devices. Even if disposable LMAs function fractionally less effectively than their longer lived counterparts, this could represent a huge increase in airway management problems. In saving lives from prion disease, we might be sacrificing lives from airway management disasters.

Fifth, we consider that reverting to the face mask would be a retrograde step. There is a very good reason why the LMA largely replaced the face mask in the 1990s: the LMA is a better airway management device (5). Again, will we be sacrificing lives?

Finally, we doubt that there would be a "huge outcry" if the public were fully informed, as the science supporting a disposable-only policy is far from compelling. We certainly agree that society should consider the risks and benefits of reusable versus disposable LMAs. Perhaps the best way to proceed is for the American Society of Anesthesiologists to form a task force for prion transmission, as it did so successfully for the management of the difficult airway (6).

References

1. Stone T, Brimacombe J, Keller C, et al. Residual protein contamination of ProSeal laryngeal mask airways after two washing protocols. Anaesth Intensive Care 2004;32:390–3.[Web of Science][Medline]
2. Clery G, Brimacombe J, Stone T, et al. Routine cleaning and autoclaving does not remove protein deposits from reusable laryngeal mask devices. Anesth Analg 2003;97:1189–91.[Abstract/Free Full Text]
3. Brimacombe J. Laryngeal mask anesthesia: principles and practice. 2nd ed. London: WB Saunders, 2004.
4. Chant K, Kociuba K, Munro R, et al. Investigation of possible patient-to-patient transmission of hepatitis C in a hospital. New South Wales Health Bulletin 1994;5:47–51.
5. Brimacombe J. The advantages of the LMA over the tracheal tube or facemask: a meta-analysis. Can J Anaesth 1995;42:1017–23.[Web of Science][Medline]
6. Practice guidelines for management of the difficult airway: a report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 1993;78:597–602.[Web of Science][Medline]

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