Year : 2008 | Volume
| Issue : 2 | Page : 58-61
Contamination problems with reuse of laryngeal mask airways and laryngoscopes
LF Chu, P Mathur, JR Trudell, JG Brock-Utne
Stanford University School of medicine, Department of Anesthesia, California, USA
J G Brock-Utne
Stanford University School of medicine, Department of Anesthesia, California
Source of Support: None, Conflict of Interest: None
|Date of Web Publication||18-Jul-2009|
| Abstract|| |
Background. In many countries around the world reusable laryngeal mask airways (LMAs) are still in use despite the availability of cheap disposable LMAs. This study was designed to determine if the technique recommended in U.S. hospitals for cleaning of LMAs and laryngoscope blades is sufficient to prevent contamination.
Materials and Methods . Previously used, cleaned, and autoclaved LMAs and laryngoscope blades were randomly collected from operating rooms and stained for 30 min at room temperature with erythrosinB dye. Two new and unused LMAs (negative controls) and two used and uncleaned LMAs (positive controls) were similarly stained. LMAs were rinsed with water and protein staining was evaluated by the investigators using specific criteria. In addition to the used and cleaned blades, an additional six used but not cleaned bladesacted as positive controls and two new blades were used as negative controls. Analysis of variance and two-tailed Fisher exact test were used to compare the difference in staining between various parts of the LMA.
Results. Our data showed that 19/19 (100%) of the used LMAs had some degree of surface protein contamination, ranging from light to heavy staining. Moderate to heavy staining was present in 14/19 (74%) of these LMAs. The location of protein stains on the inner surface, compared to the outer surface or edgeswas statistically insignificant (P>0.05). For the laryngoscope blade portion of the study, the cleaned blades were statistically indistinguishable from the blades just removed from a patient's oropharynx.
Conclusions. Cleaned, autoclaved, reusable LMAs and laryngoscope blades at a U.S.-based University hospital contained significant surface protein contamination. These results demonstrated that current cleaning methods are ineffective at removing LMA and blade surface proteins and confirm similar evidence from European hospitals. Hence reusing LMAs is not recommended. In our hospital, we now only use disposable LMAs while the laryngoscope blades follow the same cleaning protocol as before. The use of the Slater laryngoscope blade sleeves has been recommended.
Keywords: Laryngeal mask airway; Decontamination
|How to cite this article:|
Chu L F, Mathur P, Trudell J R, Brock-Utne J G. Contamination problems with reuse of laryngeal mask airways and laryngoscopes. Saudi J Anaesth 2008;2:58-61
|How to cite this URL:|
Chu L F, Mathur P, Trudell J R, Brock-Utne J G. Contamination problems with reuse of laryngeal mask airways and laryngoscopes. Saudi J Anaesth [serial online] 2008 [cited 2020 Feb 22];2:58-61. Available from: http://www.saudija.org/text.asp?2008/2/2/58/51857
| Introduction|| |
May be not surprisingly both disposable and nondisposable LMAs are reused in several countries (personal observation). This practice of reusing LMAs is mainly due to economic reasons. Contamination of reusable surgical instruments including LMAs following acceptable cleaning protocols does exist  . In the past, this protein contamination was not considered to be a concern because the proteins were rendered sterile by autoclaving or gas sterilization. However, within the past decade it was discovered that prions, a new class of infections proteins, are not rendered noninfectious by routine sterilizations techniques  .
Originally discovered by Stanley Prusiner, prions are naturally occurring proteins, which under certain conditions become unique infectious agents that can replicate without nucleic acids and can cause fatal spongiform encephalopathies in humans  . Prionborne diseases such as Kuru and Creutzfeldt-Jakob disease More Details originate from humans and require contact with infected human neuronal tissue for transmission. In 1996, a new transmissible prion disease, variant Creutzfeldt-Jakob disease (vCJD), was identified in humans in the United Kingdom  . Unlike Kuru or Creutzfeldt-Jakob, the prion responsible for vCJD was found to originate from cattle infected with bovine spongiform encephalopathy (BSE)  . Human infection with vCJD is thought to occur through consumption of BSE-infected cattle. Recently, prion proteins have been identified in high numbers in human tonsillar tissues  . The United Kingdom department of health was sufficiently concerned regarding this issue that it banned elective tonsillectomies until disposable surgical instruments could be made widely available  . The European anesthesia community has also cited concern regarding the iatrogenic spread of vCJD, specifically from reusable anesthesia equipment such as LMAs, which come into close contact with human tonsillar tissues  . One recent study of reusable anesthesia equipment in a United Kingdom hospital found significant protein contamination, even after cleaning and autoclaving  . The same is true for studies from Australia and Austria  .
The purpose of this study was to determine if protein contamination of reusable LMAs and laryngoscope blades (following routine cleaning and autoclaving using an approved protocol) is a significant clinical issue at a large U.S.-based University hospital. These results are important to anesthesiologists who reuse both non-disposable and reusable LMAs in several countries.
| Materials and Methods|| |
Following institutional approval, 19 previously used LMAs (Catalog #10140, LMA-Classic™,LMA North America, San Diego, CA), were randomly collected from Stanford University hospital operating rooms. These LMAs had been previously cleaned by designated hospital staff according to a set institutional cleaning protocol for reusable equipment. The cleaning staff was unaware that a test was going to be performed. Our institutional method of cleaning LMAs involves cleansing in mild detergent with a 0.5 inch soft cleaning brush (Part # 1701, Justman Brush Company, Omaha, NE) and autoclaving at 135 °C unwrapped for 10 min prior to placement in operating rooms. The selected LMAs were then stained for 30 min at room temperature with erythrosin B dye, a non-toxic dye which adheres to surface proteins, staining them violet-red (1.2% erythrosin B dye, Catalog # 19,826-9, SigmaAldrich Corp, St. Louis, MO). Two new and unused LMAs (negative controls) and two used and uncleaned LMAs (positive controls) were similarly stained. Stained LMAs were rinsed with water, air dried, and photographed. Protein staining was then evaluated by the investigators using specific criteria. The location and depth of staining were evaluated by the investigators. The outer surface of the LMA, inner surface (laryngeal aperture), and edges were examined and staining was subjectively rated as follows: 0, No appreciable stain; 1, Light; 2, Intermediate; 3, Dark; 4, Very Dark. A total staining score was calculated by adding three separate stain scores (0-4) of the inner surface, outer surface and edges of LMAs. For the laryngoscope section of the study, 30 laryngoscope blades were collected from the operating rooms of Stanford University hospital. Six additional, used but not cleaned blades were collected as positive controls and 2 new, unused blades were studied as negative controls.
Our institutional method of cleaning laryngoscope blades involves soaking them in a Klenzyme® solution (#1673-08, Steris Corporation, St. Louis, MO) for at least five minutes. Klenzyme® is a proprietary mixture of proteolytic enzymes. The blades were then brushed with a soft brush and rinsed with sterile water. The blades are soaked again in the Klenzyme® solution for at least 10 min and rinsed with sterile water. Finally, the blades are placed in a Steris System 1 processor that is run according to manufacturer instructions. All selected laryngoscope blades were soaked in a bath of 1% erythrosin dye for 20 min, rinsed, and then examined by three investigators. The evaluators were blinded as to the source of the blades, and were given specific criteria to score the blades. 0, no staining; 1, light staining up to 3 ml in longest dimension in only 1 area; 2, single area of staining between 3 and 10 ml or 2 separate areas of staining; 3, single area of staining greater than 10 ml or greater than 2 areas of staining. The final score for each blade was the arithmetic mean of the three individuals evaluators score.
Analysis of variance and two-tailed Fisher exact test were used to compare the differences in staining between the inner surface and the outer surface and edges of the LMA.
| Results|| |
The results of the control tests validate our staining methods as shown in [Table 1]. New unused LMAs were immersed in staining solution without retaining any erythrosin B dye [Figure 1a], while the used and uncleaned LMAs exhibited very dark staining for surface protein contamination [Figure 1b]. Examples of light to heavy surface protein staining observed in the sampled LMAs are shown in [Figure 2a], [Figure 2b], [Figure 2c], [Figure 2d].
Our data show that 19/19 (100%) of sampled LMAs showed some degree of protein staining; 74% (14/19) exhibited moderate to heavy staining [Table 1]. 26% (5/19) showed light staining, 37% (7/19) showed moderate staining, and 37% (7/19) showed heavy staining. The location of stains comparing staining of inner surface to outer surface and edges was statistically insignificant.
We also found some degree of protein staining on almost every previously used and cleaned laryngoscope blade. In general, staining was noted in the crevices around the replaceable light bulb, and at the junction of the blade with the handle. The mean score for cleaned reusable blades was 1.11 (0 being clean, 3 grossly stained) (95% confidence interval 0.86 to 1.37) while unclean blades scored 1.90 (95% CI 1.15 to 2.65) and the new blades were clean (both scored zero.) While it is important to note that the cleaned blades were statistically indistinguishable from the blades just removed from the patient's oropharynx, it is also important to note that four of the cleaned blades (13%) had a score of 2 or greater.
That indicated at least a moderate amount of staining on a significant portion of the blades that we place in patients mouths every day.
| Discussion|| |
The risk of iatrogenic spread of vCJD is difficult to assess because the number of carriers is unknown. The long incubation time between exposure and development of symptoms combined with an unknown number of exposures and incomplete penetrance have made these studies challenging. Using the number of known vCJD cases and complex mathematical modeling, investigators have projected estimates of the number carriers of vCJD. These estimates have ranged from thousands to as high as millions of people worldwide , . Recently, the U.S. had its first documented case of mad cow disease, adding to our concerns  . We have shown that once protein contamination of an LMA occurs, it is very difficult to remove even after routine prescribed cleaning methods. LMA decontamination is problematic because the silicone rubber mask readily absorbs cleaning chemicals and is sensitive to heat and harsh cleaning conditions. The manufacturer recommends only gentle cleansers and steam autoclaving to a maximum of 135 °C. Enzymatic cleansers have not been effective in removing surface protein contamination  . In addition; ethylene oxide, iodine- and phenol-based cleansers, glutaraldehyde (Cidex®) and quaternary ammonium compounds cannot be used  . Studies have shown that irradiation is completely ineffective in destroying prions  . Strong chemical agents including bleach and lye only modestly reduce infectious potential  . Conditions that may achieve complete prion inactivation, such as heating to 1000 °C for a minimum of several seconds, would destroy LMAs and many other types of reusable anesthesia equipment. Metal laryngoscope blades do not have such tight restrictions as to their cleaning methods. However, even the use of a proteolytic enzyme solution did not completely remove protein contamination. Even the more vigorous brushing possible on the stainless steel did not render them completely clean. The WHO recommends use of 1 N NaOH plus autoclaving or sodium hypochlorite for 1 hr plus autoclaving for prion contaminated material. This has not been instituted at our institution because of the difficulty of working safely and conveniently with either solution.
Our study demonstrates that routinely cleaned and autoclaved reusable LMAs contain significant surface protein contamination. The extreme resistance of prions to inactivation by heat and chemicals suggests that cleaning and autoclaving reusable LMAs may not provide significant protection from iatrogenic spread of transmissible spongiform encephalopathies such as vCJD. The clinical significance of these findings is difficult to assess given the challenges in estimating the number of potential carriers of vCJD in the United States and worldwide. One alternative to reusable LMAs is the disposable LMA-Unique™ (LMA North America, San Diego, CA). One recent study tracking the number of uses per LMA in a large university hospital found that on average, LMAs were used 517 times prior to replacement, through either loss or damage. The cost of an LMA-Unique™ ($16) compares favorably to the cost per use (excluding staff time and cleaning costs) of the LMA-Classic™ ($295 over 5-17 uses; $17-$29.50/use)  . Safe airway management is a fundamental role of the anesthesiologist. When weighing the risks and benefit of any technique, many factors must be evaluated. To this list of factors, we now add infection. Our data demonstrated significant protein contamination of routinely cleaned LMAs and laryngoscope blades. This raises concerns regarding potential iatrogenic spread of protein-born prion diseases such as vCJD. Further refinements in estimates of carrier risk will evolve as more cases of vCJD are diagnosed. We feel it is prudent to utilize disposable LMAs and the Slater laryngoscope blade sleeve (Tadco, INC., Farmington, NM 87401) until these risks are completely understood and the clinical significance of iatrogenic spread from reusable anesthesia equipment becomes more clearly defined. However, it is important to deal with this whole issue sensibly  . We have shown that cleaned autoclaved reusable LMAs laryngoscope blades contained significant protein contamination.
The importance of using disposable LMAs only once is stressed. For the laryngoscope, the Slater laryngoscope blade sleeve may prove invaluable in preventing cross infection between patients.
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[Figure 1a], [Figure 1b], [Figure 2a], [Figure 2b], [Figure 2c], [Figure 2d]