Decontamination of laryngoscope blades: Is our practice adequate?R Telang1, V Patil1, P Ranganathan1, R Kelkar2
1 Department of Anesthesiology, Critical Care and Pain, Tata Memorial Hospital, Mumbai, India
2 Department of Microbiology, Tata Memorial Hospital, Mumbai, India
Background : The laryngoscope has been identified as a potential source of cross-infection, because of blood and bacterial contamination. In India, there are no guidelines for cleaning and disinfection of anesthesia-related equipment. Practices for decontamination of laryngoscopes vary widely and in most healthcare institutes, laryngoscope blades are re-used after cleaning with tap-water. Materials and Methods: We prospectively compared two techniques for decontamination of laryngoscope blades - a) washing with tap-water and b) washing with tap-water followed by disinfection by immersing in 5% v/v (volume/volume, 1:20 dilution) aldehyde-free biguanide agent for 10 min. We calculated the cost-effectiveness of using 5% v/v aldehyde-free biguanide agent for disinfection of laryngoscopes. We also conducted a survey to assess the decontamination practices in other Indian hospitals. Results : Overall bacterial growth was 58% (29 out of 50 blades) after tap-water cleaning (of which 60% were pathogenic organisms) versus 3.4% (one out of 29 blades) after tap-water cleaning followed by immersion in disinfectant (all of which were commensals). The cost of disinfection with biguanide was Indian Rupees 1.13 (20 US cents) per laryngoscope. Most hospitals in India do not have guidelines regarding laryngoscope decontamination between uses, and cleaning with tap water is a commonly used method. Conclusion : Cleaning of laryngoscope blades with tap-water is a commonly used but inadequate method for decontamination. Washing with tap-water followed by disinfection with 5% v/v aldehyde-free biguanide for at least 10 min is an effective and inexpensive alternative. National guidelines for the decontamination of anesthesia equipment are necessary.
Keywords: Biguanide, decontamination, laryngoscope
The laryngoscope is an important instrument in the anesthetist's armamentarium. Laryngoscopy done to facilitate endotracheal tube placement is an invasive procedure involving contact with the mucous membrane, saliva and at times, blood. , A wide range of micro-organisms, including potentially harmful microbes, have been grown from routinely used laryngoscope blades. ,, The Centre for Disease Control (CDC) has determined that the potential of anesthesia equipment like laryngoscope blades for transmitting infectious agents is significant and has classified these items as semi-critical.  According to CDC recommendations, laryngoscope blades should be cleaned, followed by high-level disinfection, pasteurization, or sterilization with a US Food and Drug Administration (FDA)-approved agent. Many other professional organizations ,,, support these recommendations for disinfection of laryngoscope blades.
Inadequately disinfected laryngoscope blades and handles have been implicated in clusters of infections. ,, Blood and microbial contamination increases in patients with intraoral malignancy due to poor oral hygiene, presence of tumor and effects of treatments like radiotherapy. , This increases the potential for cross-infection if proper sterilization is not done.
Previous studies have compared various techniques for the decontamination of laryngoscopes. Orhan et al.,  demonstrated the growth of Staphylococcus aureus on laryngoscope blades cleaned with tap water. They found that cleaning of blades with tap-water followed by immersion in 2% glutaraldehyde or 10% poly vinyl pyrrolidine was an effective technique for decontamination. A study by Ballin  showed significant growth of pathogens on laryngoscope blades after washing and immersion in 4% chlorhexidine.
India is a vast country with non-uniform healthcare practices and there are no guidelines for cleaning and disinfecting anesthesia equipment. We conducted a prospective study to compare two techniques-- a) washing with tap-water and b) washing with tap-water followed by immersion in 5% v/v aldehyde-free biguanide - for adequacy of decontamination of laryngoscopes, and to calculate the costs involved in using 5% v/v aldehyde-free biguanide for disinfection of laryngoscopes. We also conducted a survey of the existing practices of decontamination of laryngoscopes among anesthesiologists in other hospitals in India.
This was a prospective study carried out over six months from March to August 2007. We selected a convenience sample of 50 consecutive patients who needed laryngoscopy and intubation during anesthesia - these included 25 patients with intra-oral malignancy and 25 patients without oral pathology. Patients with preexisting infections like Hepatitis B and C, and Human Immunodeficiency Virus (HIV) were excluded from the study. The study protocol was approved by the hospital Institutional Review Board, and written informed consent was taken from the participants.
After tracheal intubation, laryngoscope blades were examined for the presence of visible blood suggesting trauma during the procedure. After routine cleaning with tap-water (without addition of any detergent), three samples were collected by washings with 5 cc of Brain Heart Infusion broth - from the front, the back and the light bulb area of the laryngoscope blade. The blade was then immersed in 5% v/v aldehyde-free biguanide disinfectant (MedDis, MediChem International Ltd, Kent, United Kingdom) for a contact time of 10 min and subsequently rinsed with running tap-water. Samples were collected again from the same three sites. Therefore, from each laryngoscope blade, we obtained six samples - three after cleaning with water and three after washing with tap-water followed by immersion in 5% v/v aldehyde-free biguanide disinfectant. Samples were cultured aerobically on blood and MacConkey agars. Selective enrichment culture for Methicillin-resistant Staphylococcus aureus (MRSA) was carried out by incubating samples in mannitol salt agar and testing for oxycilline sensitivity. Microbial growth was assessed as:
The person who collected the samples and the microbiologist reporting on the specimens were blinded to the nature of the decontamination procedure. During the course of the study, samples of tap-water were sent everyday for microbiological analysis.
As a part of this study, we calculated the costs involved in decontamination of laryngoscopes using aldehyde-free biguanide. We also conducted a survey of "Practices of Decontamination of Laryngoscope blades" in India. We arbitrarily chose 50 delegates attending an anesthesiology conference in Mumbai, India, who were willing to participate in our survey. The survey involved a questionnaire [Annexure 1] [Additional file 1] which was filled by the participating anesthesiologists.
Data was entered into a database (SPSS 14.0, SPSS for Windows). Categorical data were analyzed using the chi-square test or Fisher's exact test.
Bacterial growth was seen on culture in 29 of 50 (58%) blades (67 of 150 samples) after cleaning with tap-water; disinfection with biguanide after washing with tap-water resulted in bacterial growth in only one of these 29 blades (3.4%) (P <0.001). The single sample which showed growth in the biguanide group showed growth of commensals. However, of the 29 blades which showed growth in the tap-water group, 15 (30%) grew pathogenic organisms (Klebsiella, Escherischia coli, Pseudomonas, Group A Streptococci, Streptococcus pneumonia) and 14 grew commensals (Bacillus species, Coagulase-negative Staphylococcus)
Blood was seen on the laryngoscope blade in 13 of 25 (52%) cases with oral cancers, and in none without oral pathology. Microbial growth was significantly (P = 0.02) higher from blades used on patients with oral cancers (19/25, 78%) compared to those with other cancers (10/25, 40%). None of the tap-water samples showed microbial growth.
Aldehyde-free biguanide solution costs Indian Rupees 845 (17 US dollars) for 250 ml. One hundred ml of biguanide (Indian Rupees 340 - 7 US dollars) was reconstituted to two liters with water, and had a shelf life of 15 days. We performed approximately 300 laryngoscopies in 15 days. The cost of disinfection per laryngoscope use was Indian Rupees 1.13 (20 US cents).
Fifty anesthesiologists from varying practice types [public hospitals - 24 (48%), nursing homes - 12 (24%), trust hospitals - 10 (20%) and private hospitals - 4 (8%)] participated in the survey. None of the hospitals had established guidelines for decontamination of laryngoscope blades. Only three of the 50 respondents used acceptable methods for disinfection of laryngoscope blades after routine surgeries. In patients with hepatitis B/C or HIV infection, 41 respondents used sterilization after proper cleaning (glutaraldehyde by 40 and autoclaving by one) whereas nine respondents used inappropriate methods like cleaning with alcohol (four) or other detergents (five). One of the questions in our survey was to ask the anesthesiologists whether they would be willing to put the laryngoscopes used by them into their own mouths and the answer was uniformly in the negative.
In the present study, we found considerable growth of pathogenic microbes on laryngoscope blades which were cleaned with tap-water after use; disinfection with aldehyde-free biguanide after washing with tap-water led to a significant decrease in contamination. The cost of using aldehyde-free biguanide for decontamination was a little more than one Indian rupee per laryngoscope. Washing with tap-water was a common method used for cleaning of laryngoscopes by anesthesiologists in several healthcare institutes across the country.
Emphasis is placed on maintaining asepsis in operation theatres and preventing transmission of infection in the peri-operative setting. Autoclaving of surgical instruments, the use of sterile gowns, hand-washing techniques and prophylactic antibiotic therapy have become routine and are considered mandatory. However, considerably less importance is given to invasive procedures like laryngoscopy and intubation, which also have the potential to transmit infection.
Despite the availability of guidelines on the subject, washing with tap-water appears to be the standard for cleaning used laryngoscopes in many hospitals in India, the possible reasons being time constraints, cost implications or lack of awareness among anesthesia professionals.
In this study we compared tap-water cleaning alone with tap-water cleaning followed by immersion in aldehyde-free biguanide for 10 min, for the disinfection of laryngoscope blades. Tap-water cleaning is essential to dislodge organic matter which may interfere with the action of the disinfectant. ,,, However, studies have shown that cleaning with tap-water alone is inadequate for decontamination.  In our study, there was significant growth of pathogenic microbes after cleaning with tap-water. Disinfection with biguanide after tap-water cleaning led to a reduction in the incidence of bacterial contamination, and specifically reduced the growth of pathogenic organisms.
Oral hygiene varies widely in patients and is dependent on social, cultural and economic factors. Suboptimal oral hygiene is common in patients with intra-oral malignancies due to the presence of the tumor, associated pain and bleeding. Advanced exophytic growths with necrosis act as a good culture medium for the growth of pathogenic organisms. In patients with intra-oral malignancies, the incidence of trauma during airway manipulation is high due to fragility of tumor tissues and thus, chances of cross-infection are increased if laryngoscopes are not adequately decontaminated. We found that the visible presence of blood and the growth of pathogenic organisms were significantly higher in patients with oral malignancy as compared to those without oral pathology.
Glutaraldehyde is a commonly-used anti-microbicidal agent. However, it has many disadvantages - irritation of skin and mucous membranes, particularly of the respiratory tract, and dermatitis after prolonged exposure. Glutaraldehyde causes organic matter present on the instrument to bond to the surface, making it difficult to remove. Side-effects of glutaraldehyde like endoscope-related colitis have been reported.  In addition, adsorption of glutaraldehyde into rubber  has been reported and can cause localized toxicity
Biguanides are disinfectants which disrupt the cell membrane of the bacterial cell and are effective against bacteria, viruses and fungi. ,, MedDis (MediChem International, UK) is an aldehyde-free polyhexamethylene biguanide derivative which is bactericidal, virucidal and fungicidal at immersion time of 10 min.  It is also sporicidal and fungicidal at contact time of 30 min and can be used to achieve high-level disinfection.  Biguanides do not have the disadvantages of glutaraldehyde.
One of the commonest problems faced in the implementation of an intervention which is an alternative to "routine practice" is objection to the additional expense involved. The low cost of the intervention in this study shows that we can deliver quality care at practically no extra charge.
The results of our survey indicate that hospitals in India do not have uniformity in cleaning procedures or guidelines for decontamination of used laryngoscopes. This is similar to the results of previous Dutch and UK surveys. , It appears that there is awareness among anesthesiologists about the hazards of using improperly sterilized equipment; however this knowledge is not implemented in the care of their patients.
Our study had certain limitations. Current recommendations ,,, advocate high-level disinfection or sterilization of semi-critical items like laryngoscope blades. At contact times of 10 min, biguanide achieves only low-level disinfection. In our study, several cases were done in patients needing diagnostic procedures for staging of head and neck cancers; in this setting, the turnover of laryngoscope blades was high and achieving ideal contact time of 30 min needed for high-level disinfection was not possible. This may be a problem in several institutes in India where the number of laryngoscopes is limited and time is a constraint. However, it should be emphasized that wherever possible, consideration should be given to achieving high-level disinfection with biguanides with a contact time of 30 min.
We restricted our study to the decontamination of laryngoscope blades; this was due to a limitation on the number of microbiological samples which could be processed. Laryngoscope handles have also been implicated as a source of contamination and possible cross-infection. Studies by Ballin,  Call,  and Simmons  found high bacterial colonization rates on laryngoscope handles, some of which were despite disinfection. It stands to reason that the laryngoscope handles in our study would also have been contaminated. Step-by-step guidelines for the cleaning and high-level disinfection and sterilization of all parts of rigid laryngoscopes were published in 2004;  however, a subsequent review article  has highlighted the lack of a consensus statement among professional organizations for the processing of laryngoscopes - especially the handles - after use, and has laid down recommendations to resolve inconsistent guidelines for the same.
Another drawback of our study was that we did not test laryngoscope blades for the presence of occult blood. Ballin et al.,  found the presence of occult blood on several laryngoscope blades which appeared free of visible blood. Several of these blades subsequently showed the growth of micro-organisms. This suggests that presence or absence of blood on the laryngoscope blade cannot be used as an indicator of the level of cleanliness.
We excluded patients with infections like HIV, Hepatitis B and C from the study. In our institute, all patients planned for invasive procedures are tested for the presence of these infections, and laryngoscope blades used on patients who test positive are autoclaved after use. Therefore, it is unlikely that any of the studied blades would have been contaminated with these organisms.
After this study, we changed the practice in our hospital and now, laryngoscope blades and handles are disinfected after use by cleaning with tap-water, followed by immersion in aldehyde-free biguanide for a contact period of at least 10 min, and preferably 30 min.
Given the societal and economic impact of peri-operative infection, it is essential that anesthesiologists and other operating room personnel use appropriate precautions to reduce the potential for transmission of infectious agents to the patients under their care.
Laryngoscopy is associated with contamination of laryngoscope blades with pathogenic organisms; this risk is significantly higher in patients with oral pathology like malignancy. Cleaning of used laryngoscope blades with tap-water alone is inadequate. Cleaning, followed by disinfection with aldehyde-free biguanide is an inexpensive alternative. Contact period of 10 min achieves low-level disinfection; longer contact times are needed to achieve current recommendations of high-level disinfection. While international guidelines on the subject are available, there is an urgent need to formulate and follow national guidelines for adequate decontamination of anesthesia-related equipment.