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Anesth Analg 2004;99:614-616
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000124033.87558.56

GENERAL ARTICLES

Potassium Permanganate Reduces Protein Contamination of Reusable Laryngeal Mask Airways

Wendy Laupu, EN*, and Joseph Brimacombe, MB ChB, FRCA, MD*,{dagger}

*Department of Anaesthesia and Intensive Care, Cairns Base Hospital, Cairns, Australia; and {dagger}James Cook University, Cairns, Australia

Address correspondence and reprint requests to Joseph Brimacombe, MB ChB, FRCA, MD, Department of Anaesthesia and Intensive Care, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia. Address e-mail to jbrimaco{at}bigpond.net.au


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
We tested the hypothesis that supplementary cleaning with potassium permanganate 2 mg/L eliminates protein deposits from reusable laryngeal mask airways (LMAs). Sixty previously used classic LMAs were hand-washed, machine-washed, dried, autoclaved, and then randomly allocated into two groups for supplementary cleaning. In Group A, the cuff was immersed in potassium permanganate 2 mg/L at 20°C for 20 min. In Group B (control), the cuff was immersed in sterile water at 20°C for 20 min. After supplementary cleaning, the LMAs were immersed in a protein staining solution and rinsed, and a high-resolution digital image was taken of the dorsal surface. The severity of staining was scored by an observer blinded to the type of supplementary cleaning. The severity of protein contamination was reduced after supplementary cleaning in potassium permanganate (P < 0.00001). Protein contamination was detected on 20% of LMAs after supplementary cleaning in potassium permanganate, compared with all LMAs in the control group. We conclude that supplementary cleaning with potassium permanganate 2 mg/L does not eliminate protein deposits from all LMAs, but it does reduce the number of devices contaminated from 100% to 20%.

IMPLICATIONS: Supplementary cleaning with potassium permanganate 2 mg/L does not eliminate protein deposits from all laryngeal mask airways, but it does reduce the number of devices contaminated from 100% to 20%.


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
New-variant Creutzfeldt-Jacob disease was first recognized having crossed the species barrier to humans in 1996 (1). It is caused by an infectious prion protein (2) that is highly resistant to decontamination by routine cleaning and autoclaving procedures (1,3). Although little is known about the risk of cross-infection from reusable surgical and anesthesia equipment, perhaps all equipment should be disposable (4,5); however, disposable equipment may not function as well (6). One of the most common reusable items of anesthesia equipment is the laryngeal mask airway (LMA), but routine cleaning and sterilization (4,7,8)—and even supplementary cleaning with guided scrubbing or ultrasonic cleaning (9)—does not remove protein contamination from reusable LMA devices. We tested the hypothesis that supplementary cleaning with potassium permanganate 2 mg/L eliminates protein deposits from the LMA.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
Sixty previously used ClassicTM LMAs (Laryngeal Mask Co., Henley-on-Thames, UK) were tested at the end of a working day (20–40 uses; preuse check tests were passed) (10). Each LMA was cleaned and sterilized as follows: 1) immersion in a mild enzymatic solution (Enzyme Rapid; 3M, Pymble, Australia) for 3 min; 2) washing the external surfaces with a cloth for at least 1 min or until all visible material was removed; 3) washing the airway tube with a soft bristled brush or until all visible material was removed; 4) placing the LMA in an automatic washer for 14 min, which included warm washing at 55°C with a disinfectant and hot washing at 85°C; 5) placing in a dryer for 30 min at 75°C; and 6) autoclaving at 134°C for 4 min at 206 kPa.

The LMAs were randomly allocated (by opening an opaque envelope) into two equal-sized groups for supplementary cleaning. In Group A, the cuff was immersed in potassium permanganate 2 mg/L at 20°C for 20 min. In Group B (control), the cuff was immersed in sterile water at 20°C for 20 min. After supplementary cleaning, the LMAs were immersed for 30 min in a protein staining solution (1.2% erythrosin B) (11) and rinsed in sterile water at 20°C for 1 min, and a high-resolution digital image (3.3 megapixels) was taken of the dorsal surface. The severity of staining was scored according to the percentage of area stained: none (0%), mild (>0%–25%), moderate (>25%–50%), heavy (>50%–75%), and severe (>75%). The images were analyzed by an observer blinded to the type of supplementary cleaning. Sample size was selected for a Type I error of 0.05 and a power of 0.95. Statistical analysis was performed with the {chi}2 test.


   Results
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 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
Data on the severity of staining are given in Table 1. The severity of protein contamination was reduced after supplementary cleaning in potassium permanganate ({chi}2 = 43; P < 0.00001). Protein contamination was detected on six LMAs after supplementary cleaning in potassium permanganate compared with all LMAs in the control group.


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  		Table 1. Severity of Staining
 

   Discussion
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 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
There are four studies which have examined protein contamination with reusable LMAs. Miller et al. (4), Chu et al. (7), and Clery et al. (8) found that all reusable LMAs had some protein contamination after routine cleaning and autoclaving. Coetzee (9) found that systematic cleaning and scrubbing was more effective than routine cleaning, but only for accessible locations, and that ultrasonic cleaning was more effective than routine cleaning, but only for inaccessible locations; however, none of these techniques eliminated staining altogether. In contrast, we found that potassium permanganate 2 mg/L eliminated protein deposits from 80% of reusable LMAs.

Potassium permanganate, also known as chameleon mineral, is a powerful antioxidant that chemically burns up organic material. It is widely used as a disinfectant when diluted with water or acetone. It has been used in humans to treat leg venous ulcers (12) and psoriasis (13) and as an abortifacient (14). Interestingly, Kimberlin et al. (15), in a 1983 study, found that potassium permanganate 2 mg/L reduced the infectivity titer of mouse-passaged scrapie, but it was not considered sufficiently powerful to be used as a decontaminant.

A limitation of our study is that we did not quantify the mass of residual protein removed by the potassium permanganate. This is a difficult measurement to make because the protein is too adherent to be dissolved into solution for a protein assay. However, an approximation of the amount removed can be made by assuming that the density of protein staining is uniform and that the actual area of staining for mild (0%–25%), moderate (25%–50%), and heavy (50%–75%) is the midpoint of these values, that is, 12.5%, 37.5%, and 62.5%, respectively. A simple calculation reveals that the average area of staining per LMA after permanganate was 2.5% [(12.5% x 6)/30] and after saline was 29% [(12.5% x 13 + 37.5 x 14 = 62.5 x 3)/30], suggesting that potassium permanganate removes 91% (26.5/29) of residual protein.

It is not known whether potassium permanganate reduces the longevity of reusable LMAs, but bench testing by one of the authors (JB) revealed no change in elastance after 10 cleaning/autoclaving cycles, which included soaking in potassium permanganate. Also, potassium permanganate is recommended by some manufacturers for cleaning silicone tubing (ESCO technical data catalog; http:// www.bibby-sterilin.com/cat/esco/esctids1.htm).

To prevent patient-to-patient transmission, it has been suggested that all patients should be screened for prion disease or that all equipment should be disposable; however, the economic consequences of each of these options on the health care system would be enormous. Tordoff and Scott (16) suggested that when considering the relative risks and options, we should ask ourselves whether we would use a second-hand LMA on our children and then follow the "golden rule." Work is urgently required to determine the risk of infection so that evidence-based policies can be made; however, in the meantime, we consider that there is no justification for abandoning the use of clinically proven reusable LMA devices for clinically unproven disposable LMA devices. Patients with suspected new-variant Creutzfeldt-Jacob disease should be managed with disposable airway devices provided that they are functionally comparable to their reusable counterparts; if a reusable device is used, it should be discarded. Supplementary cleaning of reusable LMA devices in potassium permanganate 2 mg/L should reduce the infection risk, but it is not sufficiently effective to permit the safe reuse of an LMA that has been exposed to prion proteins.

We conclude that supplementary cleaning with potassium permanganate 2 mg/L does not eliminate protein deposits from all LMAs, but it does reduce the number of devices contaminated from 100% to 20%.


   Acknowledgments
 
We thank V. Maguire, J. Batey, and G. Laupu for their assistance.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Will RG, Ironside JW, Zeidler M. A new variant of Creutzfeldt-Jacob disease in the UK. Lancet 1996; 347: 921–5.[Web of Science][Medline]
  2. Haltia M. Human prion diseases. Ann Med 2000; 32: 493–500.[Medline]
  3. Hilton DA. VCJD: predicting the future? Neuropathol Appl Neurobiol 2000; 26: 405–7.[Medline]
  4. 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]
  5. Smith G. Variant CJD: what you need to know at present. R Coll Anaesthetists Bull 2001; 302–4.
  6. Blunt MC, Burchett KR. Variant Creutzfeldt disease and disposable anaesthetic equipment: balancing the risks. Br J Anaesth 2003; 90: 1–3.[Free Full Text]
  7. Chu LF, Trudell JR, Brock Utne JG. Autoclaved reusable laryngeal mask airways contain significant protein contamination [abstract]. Anesthesiology 2002; 96: A570.
  8. Clery G, Brimacombe J, Stone T, et al. Routine cleaning and autoclaving does not remove protein deposits from re-usable laryngeal mask devices. Anesth Analg 2003; 97: 1189–91.[Abstract/Free Full Text]
  9. 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]
  10. Verghese C. LMA-ClassicTM, LMA-FlexibleTM, LMA-UniqueTM: instruction manual. Henley-on-Thames, UK: Laryngeal Mask Co Ltd, 1999.
  11. Leknes KN, Lie T. Erythrosin staining in clinical disclosure of plaque. Quintessence Int 1998; 19: 199–204.
  12. Hansson C, Faergemann J. The effect of antiseptic solutions on microorganisms in venous leg ulcers. Acta Derm Venereol 1995; 75: 31–3.[Web of Science][Medline]
  13. Huntley AC. Oral ingestion of potassium permanganate or aluminum acetate in two patients. Arch Dermatol 1984; 120: 1363–5.[Abstract/Free Full Text]
  14. Aguilar G, Repper C, Reyes C. Considerations on 200 cases of vaginal burns by potassium permanganate. Ginecol Obstet Mex 1971; 29: 275–9.[Medline]
  15. Kimberlin RH, Walker CA, Millson GC, et al. Disinfection studies with two strains of mouse-passaged scrapie agent: guidelines for Creutzfeldt-Jakob and related agents. J Neurol Sci 1983; 59: 355–69.[Medline]
  16. Tordoff SG, Scott S. Blood contamination of the laryngeal mask airways and laryngoscopes: what do we tell our patients? Anaesthesia 2002; 57: 505–6.
Accepted for publication February 5, 2004.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins and Stanford University Libraries' HighWire Press®. Copyright 2004 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press