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LETTERS TO THE EDITOR

Proteinaceous Material on Routinely Cleaned Laryngeal Mask Airways

Department of Anesthesiology and Critical Care, University of Stellenbosch, Tygerberg, South Africa

To the Editor:

In a study published earlier in 2003 (1), use of erythromycin does not lead to more effective removal of proteinaceous material from reusable laryngeal mask airways (LMA). Systematic cleaning and scrubbing leads to effective but not complete removal of proteinaceous material from surfaces other than the grid area of the LMA, and that ultrasonic cleaning is more effective than other methods in removing proteinaceous material from the those areas of the mask most inaccessible, such as the grid (1). These results confirmed those of Miller et al. (2), and is now confirmed by Clery et al. (3). None of the methods used in these studies achieved optimal cleaning of LMAs.

Clery et al. do not mention whether LMAs in their study had been subjected to the vigorous cleaning method described from the onset of use, neither do they mention how many of these vigorous cleaning cycles the LMAs had been subjected to. It is not known what the effect of autoclaving or drying is on the residual protein. Neither is it known whether the LMA surface becomes more susceptible to proteins with repeated use.

The theoretical risk of transmission of spongiform encephalopathies has led to an editorial where it is mentioned that the Working Party of the Association of Anesthetists of Great Britain and Ireland is investigating methods to reduce the risk of cross-infection in patients undergoing anesthesia, ideally by single-use equipment where practical (4). As Tordoff and Scott (5) point out, what should we tell our patients when we use a second-hand laryngeal mask? If there is Risk of transmission of BSE, we might only know in 20 years time.

Clery et al. (3) is supported in their observation that work is required to determine the risk of infection, but I feel that perhaps more than routine cleaning and autoclaving is needed to render the LMA free of proteinaceous material, and that the current studies have merely pointed out the inadequacy of current methods..

References

1. Coetzee GJ. Eliminating protein from reusable laryngeal mask airways: a study comparing routinely cleaned masks with three alternative cleaning methods. Anaesthesia 2003; 58: 346–53.[Web of Science][Medline]
2. Miller DM, Youkhana I, Karunaratne WU, Pearce A. Presence of protein deposits on ‘cleaned’ re-usable anaesthetic equipment. Anaesthesia 2001; 56: 1069–72.[Web of Science][Medline]
3. 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]
4. Blunt MC, Burchett KR. Variant Creutzfeldt-Jacob disease and disposable anaesthetic equipment: balancing the risks. Br J Anaesth 2003; 90: 1–3.[Free Full Text]
5. Tordoff SG, Scott S. Blood contamination of laryngeal mask airways and laryngoscopes: what do we tell our patients? Anaesthesia 2002; 57: 505.

Response

Department of Anaesthesia and Intensive Care, Cairns Base Hospital, Cairns, Australia Department of Anaesthesia and Intensive Care Medicine, Leopold-Franzens University, Innsbruck, Austria

In Response:

We would like to thank Dr Coetzee for his comments about our article, and for bringing attention to his excellent study comparing cleaning methods for reusable LMAs (1). We did not document the number of uses of the LMAs before testing; however, we recently found that the average number of uses of an adult-sized classic LMA in circulation at our institute is 37. All our LMAs would have undergone the same cleaning and sterilization processes described in our study from the outset, as these processes have been the standard of practice at out institute for many years. Interestingly, Stone et al. (2) found that there is no correlation between number of uses and the level of contamination for the ProSeal laryngeal mask airway.

While agreeing that most studies have merely pointed out the inadequacy of current cleaning methods, we should take cheer in the fact that more effective cleaning is possible. Coetzee himself (1) showed that systematic cleaning and scrubbing, and ultrasonic cleaning facilitated removal of protein deposits; and Laupu and myself (3) showed that potassium permanganate 2 mg/L removes 91% of residual protein. We are optimistic that a method will eventually be found to eliminate protein deposits from reusable LMAs. We only hope that when this Holy Grail of prion disease prevention is found, it will be both economic and practical.

References

1. Coetzee GJ. Eliminating protein from reusable laryngeal mask airways: a study comparing routinely cleaned masks with three alternative cleaning methods. Anaesthesia 2003; 58: 346–53.
2. Stone T, Brimacombe J, Keller C, et al. Machine washing does not augment hand washing in the removal of protein contamination from the ProSeal^TM laryngeal mask airway. Anaesth Intensive Care. In press.
3. Laupu W, Brimacombe J. Potassium permanganate reduces protein contamination of reusable LMAs. Anesth Analg. In press.

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