Which instruments and equipment must be sterilized

Journal Article

William A. Rutala,

Hospital Epidemiology, University of North Carolina Health Care System, and Division of Infectious Diseases, University of North Carolina School of Medicine

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Chapel Hill

Reprints or correspondence: Dr. William A. Rutala, Div. of Infectious Diseases, 130 Mason Farm Rd., Bioinformatics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7030 [].

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Published:

01 September 2004

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  William A. Rutala, David J. Weber, Disinfection and Sterilization in Health Care Facilities: What Clinicians Need to Know, Clinical Infectious Diseases, Volume 39, Issue 5, 1 September 2004, Pages 702–709, //doi.org/10.1086/423182

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Abstract

In 1996 in the United States, ∼46,500,000 surgical procedures and an even larger number of invasive medical procedures were performed [1]. For example, ∼5 million gastrointestinal endoscopies are performed per year [1]. Each of these procedures involves contact by a medical device or surgical instrument with a patient's sterile tissue or mucous membranes. A major risk of all such procedures is the introduction of pathogenic microbes, which can lead to infection. For example, failure to properly disinfect or sterilize equipment may lead to person-to-person transmission via contaminated devices [e.g., Mycobacterium tuberculosis—contaminated bronchoscopes].

Achieving disinfection and sterilization through the use of disinfectants and sterilization practices is essential for ensuring that medical and surgical instruments do not transmit infectious pathogens to patients. Because it is not necessary to sterilize all patient-care items, health care policies must identify whether cleaning, disinfection, or sterilization is indicated, primarily on the basis of each item's intended use.

Multiple studies in many countries have documented lack of compliance with established guidelines for disinfection and sterilization [2, 3]. Failure to comply with scientifically based guidelines has led to numerous outbreaks of infection [3–7]. In this article, a pragmatic approach to the judicious selection and proper use of disinfection and sterilization processes is presented that is based on the results of well-designed studies assessing the efficacy [via laboratory investigations] and effectiveness [via clinical studies] of disinfection and sterilization procedures.

A Rational Approach to Disinfection and Sterilization

More than 35 years ago, Spaulding [8] devised a rational approach to disinfection and sterilization of patient-care items or equipment. This classification scheme is so clear and logical that it has been retained, refined, and successfully used by infection-control professionals and others when planning methods for disinfection or sterilization [9–15]. Spaulding believed that the nature of disinfection could be understood more readily if instruments and items for patient care were divided into 3 categories—namely, critical, semicritical, and noncritical—on the basis of the degree of risk of infection involved in the use of the items. This terminology is employed by the Centers for Disease Control and Prevention [CDC] in the documents “Guidelines for Environmental Infection Control in Health-Care Facilities” [16] and “Guideline for Disinfection and Sterilization in Healthcare Facilities” [14].

Critical items. Critical items are those associated with a high risk of infection if the item is contaminated with any microorganism, including bacterial spores. Thus, sterilization of objects that enter sterile tissue or the vascular system is critical, because any microbial contamination could result in disease transmission. This category includes surgical instruments, cardiac and urinary catheters, implants, and ultrasound probes used in sterile body cavities. The items in this category should be purchased as sterile or should be sterilized by steam sterilization, if possible. If the item is heat sensitive, it may be treated with ethylene oxide [ETO] or hydrogen peroxide gas plasma or with liquid chemical sterilants if other methods are unsuitable. Tables 1 and 2 list several germicides that are categorized as chemical sterilants. These include ⩾2.4% glutaraldehyde—based formulations, 1.12% glutaraldehyde with 1.93% phenol/phenate, 7.5% stabilized hydrogen peroxide, 7.35% hydrogen peroxide with 0.23% peracetic acid, ⩾0.2% peracetic acid, and 1.0% hydrogen peroxide with 0.08% peracetic acid. The indicated exposure times are within the range 3–12 h, with the exception of ⩾0.2% peracetic acid [sporicidal time of 12 min at 50°C–56°C] [19]. Use of liquid chemical sterilants is a reliable method of sterilization only if cleaning precedes treatment, which eliminates organic and inorganic material, and if the proper guidelines for concentration, contact time, temperature, and pH are followed. Another limitation to sterilization of devices with liquid chemical sterilants is that the devices cannot be wrapped during processing in the liquid chemical sterilant; thus, maintaining sterility after processing and during storage is impossible. Furthermore, after exposure to the liquid chemical sterilant, devices may require rinsing with water that, in general, is not sterile. Therefore, because of the inherent limitations of the use of liquid chemical sterilants in a nonautomated reprocessor, their use should be restricted to reprocessing critical devices that are heat sensitive and incompatible with other sterilization methods.

Table 1

Methods for disinfection and sterilization of patient-care items and environmental surfaces.

Table 2

Summary of advantages and disadvantages of chemical agents used as chemical sterilants or as high-level disinfectants.

Semicritical items. Semicritical items are those that come in contact with mucous membranes or nonintact skin. Respiratory-therapy and anesthesia equipment, some endoscopes, laryngoscope blades, esophageal manometry probes, anorectal manometry catheters, and diaphragm-fitting rings are included in this category. These medical devices should be free of all microorganisms [i.e., mycobacteria, fungi, viruses, and bacteria], although small numbers of bacterial spores may be present. In general, intact mucous membranes, such as those of the lungs or the gastrointestinal tract, are resistant to infection by common bacterial spores but are susceptible to other organisms, such as bacteria, mycobacteria, and viruses. The minimum requirement for semicritical items is high-level disinfection using chemical disinfectants. Glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde [OPA], peracetic acid with hydrogen peroxide, and chlorine have been cleared by the US Food and Drug Administration [FDA] [19] and are dependable high-level disinfectants when guidelines for effective germicidal procedures are followed [tables 1 and 2]. The exposure time for most high-level disinfectants varies from 10 to 45 min, at 20°C–25°C. Outbreaks of infection continue to occur when ineffective disinfectants, including iodophor, alcohol, and over-diluted glutaraldehyde [5], are used for so-called high-level disinfection. When a disinfectant is selected for use with certain patient-care items, the chemical compatibility after extended use with the items to be disinfected must also be considered. For example, compatibility testing by Olympus America of 7.5% hydrogen peroxide showed cosmetic and functional changes in the tested endoscopes [Olympus America, personal communication]. Similarly, Olympus America does not endorse the use of products containing hydrogen peroxide with peracetic acid, because of cosmetic and functional damage [Olympus America, personal communication].

Semicritical items that will have contact with the mucous membranes of the respiratory or gastrointestinal tract should be rinsed with sterile water, filtered water, or tap water, followed by an alcohol rinse [14, 20, 21]. An alcohol rinse and forced-air drying markedly reduces the likelihood of contamination of the instrument [e.g., endoscopes], most likely by eliminating the wet environment favorable to bacterial growth [21]. After rinsing, items should be dried and then stored in a manner that protects them from damage or contamination. There is no recommendation to use sterile or filtered water, rather than tap water, for rinsing semicritical equipment that will have contact with the mucous membranes of the rectum [e.g., rectal probes or anoscopes] or vagina [e.g., vaginal probes] [14].

Noncritical items. Noncritical items are those that come in contact with intact skin but not mucous membranes. Intact skin acts as an effective barrier to most microorganisms; therefore, the sterility of items coming in contact with intact skin is “not critical.” Examples of noncritical items are bedpans, blood-pressure cuffs, crutches, bed rails, linens, bedside tables, patient furniture, and floors. In contrast to critical and some semicritical items, most noncritical reusable items may be decontaminated where they are used and do not need to be transported to a central processing area. There is virtually no documented risk of transmitting infectious agents to patients via noncritical items [22] when they are used as noncritical items and do not contact nonintact skin and/or mucous membranes. However, these items [e.g., bedside tables or bed rails] could potentially contribute to secondary transmission, by contaminating the hands of health care workers or by contact with medical equipment that will subsequently come in contact with patients [23]. Table 1 lists several low-level disinfectants that may be used for noncritical items. The exposure times for these disinfectants are 60 s or longer.

Current Issues in Disinfection and Sterilization

Reprocessing of endoscopes. Physicians use endoscopes to diagnose and treat numerous medical disorders. Although endoscopes are a valuable diagnostic and therapeutic tool in modern medicine and although the incidence of infection associated with their use has been reported to be very low [∼1 in 1.8 million procedures] [24], more health care—associated outbreaks of infection have been linked to contaminated endoscopes than to any other medical device [3–5]. To prevent the spread of health care—associated infection, all heat-sensitive endoscopes [e.g., gastrointestinal endoscopes, bronchoscopes, and nasopharyngoscopes] must be properly cleaned and, at a minimum, subjected to high-level disinfection after each use. High-level disinfection can be expected to destroy all microorganisms, although a few bacterial spores may survive when high numbers of spores are present.

Recommendations for the cleaning and disinfection of endoscopic equipment have been published and should be strictly followed [14, 20]. Unfortunately, audits have shown that personnel do not adhere to guidelines on reprocessing [25–27] and that outbreaks of infection continue to occur [28, 29]. To ensure that the personnel responsible for reprocessing are properly trained, initial and annual competency testing should be required for each individual who is involved in reprocessing endoscopic instruments [14, 20, 21, 30].

In general, endoscope disinfection or sterilization with a liquid chemical sterilant or high-level disinfectant involves the following 5 steps, which should be performed after leak testing: [1] clean: mechanically clean internal and external surfaces, including brushing internal channels and flushing each internal channel with water and an enzymatic cleaner; [2] disinfect: immerse endoscope in high-level disinfectant [or chemical sterilant], perfuse disinfectant [which eliminates air pockets and ensures contact of the germicide with the internal channels] into all accessible channels, such as the suction/biopsy channel and the air/water channel, and expose endoscope for the time recommended for specific products; [3] rinse: rinse the endoscope and all channels with sterile water, filtered water [commonly used with automated endoscope reprocessors], or tap water; [4] dry: rinse the insertion tube and inner channels with alcohol and dry with forced air, after disinfection and before storage; and [5] store: store the endoscope in a way that prevents recontamination and promotes drying [e.g., hung vertically].

Unfortunately, there is poor compliance with the recommendations for reprocessing endoscopes. In addition, in rare instances, the scientific literature and recommendations from professional organizations regarding the use of disinfectants and sterilants may differ from claims on the manufacturer's label. One example is the contact time used to achieve high-level disinfection with 2% glutaraldehyde. On the basis of FDA requirements [the FDA regulates liquid sterilants and high-level disinfectants used on critical and semicritical medical devices], manufacturers test the efficacy of their germicide formulations under worst-case conditions [i.e., minimum recommended concentration of the active ingredient] and in the presence of organic soil [typically, 5% serum]. The soil represents the organic loading to which the device is exposed during actual use and that would remain on the device in the absence of cleaning. These stringent test conditions are designed to provide a margin of safety, by assuring that the contact conditions for the germicide provide complete elimination of the test bacteria [e.g., 105–106 cfu M. tuberculosis in organic soil and dried on a scope] if inoculated into the most difficult areas for the disinfectant to penetrate and in the absence of cleaning. However, the scientific data demonstrate that M. tuberculosis levels can be reduced by at least 8 log10 cfu with cleaning [reduction of 4 log10 cfu] followed by chemical disinfection for 20 min at 20°C [reduction of 4–6 log10 cfu] [14, 15, 19, 20, 31]. Because of these data, professional organizations [at least 14 worldwide] that have endorsed an endoscope-reprocessing guideline recommend contact with 2% glutaraldehyde for 20 min [or