BRIEF REPORT

Potassium Permanganate Reduces Protein Contamination ofReusable Laryngeal Mask AirwaysWendy Laupu, EN*, and Joseph Brimacombe, MB ChB, FRCA, MD*†

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

We tested the hypothesis that supplementary cleaningwith potassium permanganate 2 mg/L eliminates pro-tein deposits from reusable laryngeal mask airways(LMAs). Sixty previously used classic LMAs werehand-washed, machine-washed, dried, autoclaved,and then randomly allocated into two groups for sup-plementary cleaning. In Group A, the cuff was im-mersed in potassium permanganate 2 mg/L at 20°C for20 min. In Group B (control), the cuff was immersed insterile water at 20°C for 20 min. After supplementarycleaning, the LMAs were immersed in a protein stain-ing solution and rinsed, and a high-resolution digitalimage was taken of the dorsal surface. The severity of

staining was scored by an observer blinded to the typeof supplementary cleaning. The severity of protein con-tamination was reduced after supplementary cleaningin potassium permanganate (P � 0.00001). Protein con-tamination was detected on 20% of LMAs after supple-mentary cleaning in potassium permanganate, com-pared with all LMAs in the control group. We concludethat supplementary cleaning with potassium perman-ganate 2 mg/L does not eliminate protein depositsfrom all LMAs, but it does reduce the number of devicescontaminated from 100% to 20%.

(Anesth Analg 2004;99:614–6)

N ew-variant Creutzfeldt-Jacob disease was firstrecognized having crossed the species barrier tohumans in 1996 (1). It is caused by an infectious

prion protein (2) that is highly resistant to decontam-ination by routine cleaning and autoclaving proce-dures (1,3). Although little is known about the risk ofcross-infection from reusable surgical and anesthesiaequipment, perhaps all equipment should be dispos-able (4,5); however, disposable equipment may notfunction as well (6). One of the most common reusableitems of anesthesia equipment is the laryngeal maskairway (LMA), but routine cleaning and sterilization(4,7,8)—and even supplementary cleaning withguided scrubbing or ultrasonic cleaning (9)—does notremove protein contamination from reusable LMAdevices. We tested the hypothesis that supplementarycleaning with potassium permanganate 2 mg/L elim-inates protein deposits from the LMA.

MethodsSixty previously used Classic™ LMAs (Laryngeal MaskCo., Henley-on-Thames, UK) were tested at the end of aworking day (20–40 uses; preuse check tests werepassed) (10). Each LMA was cleaned and sterilized asfollows: 1) immersion in a mild enzymatic solution (En-zyme Rapid; 3M, Pymble, Australia) for 3 min; 2) wash-ing the external surfaces with a cloth for at least 1 min oruntil all visible material was removed; 3) washing theairway tube with a soft bristled brush or until all visiblematerial was removed; 4) placing the LMA in an auto-matic washer for 14 min, which included warm washingat 55°C with a disinfectant and hot washing at 85°C; 5)placing in a dryer for 30 min at 75°C; and 6) autoclavingat 134°C for 4 min at 206 kPa.

The LMAs were randomly allocated (by opening anopaque envelope) into two equal-sized groups forsupplementary cleaning. In Group A, the cuff wasimmersed in potassium permanganate 2 mg/L at 20°Cfor 20 min. In Group B (control), the cuff was im-mersed in sterile water at 20°C for 20 min. After sup-plementary cleaning, the LMAs were immersed for30 min in a protein staining solution (1.2% erythrosinB) (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 stain-ing was scored according to the percentage of area

Accepted for publication February 5, 2004.Address correspondence and reprint requests to Joseph Brima-

combe, MB ChB, FRCA, MD, Department of Anaesthesia and In-tensive Care, Cairns Base Hospital, The Esplanade, Cairns 4870,Australia. Address e-mail to jbrimaco@bigpond.net.au.

DOI: 10.1213/01.ANE.0000124033.87558.56

©2004 by the International Anesthesia Research Society614 Anesth Analg 2004;99:614–6 0003-2999/04

stained: none (0%), mild (�0%–25%), moderate(�25%–50%), heavy (�50%–75%), and severe (�75%).The images were analyzed by an observer blinded tothe type of supplementary cleaning. Sample size wasselected for a Type I error of 0.05 and a power of 0.95.Statistical analysis was performed with the �2 test.

ResultsData on the severity of staining are given in Table 1.The severity of protein contamination was reducedafter supplementary cleaning in potassium permanga-nate (�2 � 43; P � 0.00001). Protein contamination wasdetected on six LMAs after supplementary cleaning inpotassium permanganate compared with all LMAs inthe control group.

DiscussionThere are four studies which have examined proteincontamination with reusable LMAs. Miller et al. (4),Chu et al. (7), and Clery et al. (8) found that allreusable LMAs had some protein contamination afterroutine cleaning and autoclaving. Coetzee (9) foundthat systematic cleaning and scrubbing was more ef-fective than routine cleaning, but only for accessiblelocations, and that ultrasonic cleaning was more effec-tive than routine cleaning, but only for inaccessiblelocations; however, none of these techniques elimi-nated staining altogether. In contrast, we found thatpotassium permanganate 2 mg/L eliminated proteindeposits from 80% of reusable LMAs.

Potassium permanganate, also known as chameleonmineral, is a powerful antioxidant that chemicallyburns up organic material. It is widely used as adisinfectant when diluted with water or acetone. It hasbeen used in humans to treat leg venous ulcers (12)and psoriasis (13) and as an abortifacient (14). Inter-estingly, Kimberlin et al. (15), in a 1983 study, foundthat potassium permanganate 2 mg/L reduced theinfectivity titer of mouse-passaged scrapie, but it wasnot considered sufficiently powerful to be used as adecontaminant.

A limitation of our study is that we did not quantifythe mass of residual protein removed by the potas-sium permanganate. This is a difficult measurement tomake because the protein is too adherent to be dis-solved into solution for a protein assay. However, anapproximation of the amount removed can be madeby assuming that the density of protein staining isuniform 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 calculationreveals that the average area of staining per LMA afterpermanganate was 2.5% [(12.5% � 6)/30] and after

saline was 29% [(12.5% � 13 � 37.5 � 14 � 62.5 �3)/30], suggesting that potassium permanganate re-moves 91% (26.5/29) of residual protein.

It is not known whether potassium permanganatereduces the longevity of reusable LMAs, but benchtesting by one of the authors (JB) revealed no changein elastance after 10 cleaning/autoclaving cycles,which included soaking in potassium permanga-nate. Also, potassium permanganate is recom-mended by some manufacturers for cleaning sili-cone tubing (ESCO technical data catalog; http://www.bibby-sterilin.com/cat/esco/esctids1.htm).

To prevent patient-to-patient transmission, it hasbeen suggested that all patients should be screened forprion disease or that all equipment should be dispos-able; however, the economic consequences of each ofthese options on the health care system would beenormous. Tordoff and Scott (16) suggested that whenconsidering the relative risks and options, we shouldask ourselves whether we would use a second-handLMA on our children and then follow the “goldenrule.” Work is urgently required to determine the riskof infection so that evidence-based policies can bemade; however, in the meantime, we consider thatthere is no justification for abandoning the use ofclinically proven reusable LMA devices for clinicallyunproven disposable LMA devices. Patients with sus-pected new-variant Creutzfeldt-Jacob disease shouldbe managed with disposable airway devices providedthat they are functionally comparable to their reusablecounterparts; if a reusable device is used, it should bediscarded. Supplementary cleaning of reusable LMAdevices in potassium permanganate 2 mg/L shouldreduce the infection risk, but it is not sufficiently ef-fective to permit the safe reuse of an LMA that hasbeen exposed to prion proteins.

We conclude that supplementary cleaning with po-tassium permanganate 2 mg/L does not eliminateprotein deposits from all LMAs, but it does reduce thenumber of devices contaminated from 100% to 20%.

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

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Jacob disease in the UK. Lancet 1996;347:921–5.

Table 1. Severity of Staining

Variable Permanganate Control

None 24 (80) 0 (0)Mild 6 (20) 13 (43)Moderate 0 (0) 14 (46)Heavy 0 (0) 3 (10)Severe 0 (0) 0 (0)

Data are n (%).

ANESTH ANALG BRIEF REPORT 6152004;99:614–6

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12. Hansson C, Faergemann J. The effect of antiseptic solutions onmicroorganisms in venous leg ulcers. Acta Derm Venereol 1995;75:31–3.

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14. Aguilar G, Repper C, Reyes C. Considerations on 200 cases ofvaginal burns by potassium permanganate. Ginecol Obstet Mex1971;29:275–9.

15. Kimberlin RH, Walker CA, Millson GC, et al. Disinfection stud-ies with two strains of mouse-passaged scrapie agent: guide-lines for Creutzfeldt-Jakob and related agents. J Neurol Sci1983;59:355–69.

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