Chapter Outline
The Spaulding Classification of Equipment for Disinfection and Sterilization 330
Disinfection of Healthcare Devices 331
Limitations of the Spaulding Classification System 333
Special Considerations for Fiberoptic Endoscopes 333
Considerations for Bloodborne Pathogens and Antibiotic-Resistant Bacteria 333
Occupational Exposure to Disinfectants 334
Federal Regulation of Chemicals Used for Disinfection 335
Single-Use Devices 335
Prevention of Patient Infections Associated with Equipment 336
Patients and healthcare providers expect that surgical and invasive diagnostic or therapeutic procedures will not lead to infection. In the United States, there are more than 45 million surgical and invasive procedures performed annually, and lapses in infection control procedures may have devastating consequences producing patient morbidity or mortality. Based on estimates made by the Centers for Disease Control and Prevention (CDC), healthcare-associated infections (HAI) are one of the top 10 causes of death in the United States and produce a significant financial impact on the healthcare system.
Proper disinfection or sterilization of equipment is critical for preventing healthcare-related infection. The description of a recent outbreak of infection after thoracic surgery clearly illustrates the importance of adherence to accepted protocols. Seven patients having thoracic or cardiac anesthesia developed Pseudomonas aeruginosa pneumonia or bronchitis within several days after surgery. Investigation of several possible sources indicated that bronchoscopes used by anesthesiologists for placement of double lumen endotracheal tubes had not been properly disinfected after use. Inadequate cleaning of the used bronchoscopes and a problem with the automated equipment used for disinfection resulted in residual bacterial contamination of the bronchoscopes after processing. The pathogens remaining on the inadequately disinfected scopes were subsequently transmitted to several patients. Identification and correction of the flaws in the cleaning and disinfection processes terminated the outbreak.
The Spaulding Classification of Equipment for Disinfection and Sterilization
Infection control practitioners have used a classification scheme proposed by Earle Spaulding for determining appropriate disinfection and sterilization of patient care equipment. This approach has been generally accepted by the CDC and is contained in their most recent guidelines. Spaulding categorized devices as critical, semicritical, and noncritical corresponding to the risk of infection associated with its use. The greatest risk for infection is associated with contaminated critical items because these are devices that enter the patients’ sterile tissue or vascular system. Examples of critical devices include surgical instruments and vascular or urinary catheters. Semicritical items are those that contact mucous membranes or nonintact skin and include the majority of devices used in respiratory therapy and anesthesiology. Examples of semicritical items include the following: laryngoscope blades, esophageal stethoscopes, suction catheters, oral and nasal airways, and laryngeal mask airways. Noncritical items are devices that either do not touch the patient or contact only intact skin, but not mucous membranes and do not enter sterile tissues. Noncritical patient care items include devices such as blood pressure cuffs, pulse oximeter probes, and electrocardiogram (ECG) cables. Environmental surfaces can be considered noncritical items and include hospital beds and stretchers, the surface of the anesthesia machine, and laryngoscope handles. Since intact skin should provide an effective barrier to most pathogens, noncritical items are associated with a lower risk of infection, but they can serve as an environmental reservoir for pathogens. Because noncritical items are frequently touched by healthcare workers, secondary transmission of pathogens can occur to patients via contaminated hands or gloves.
Cleaning
A reduction in the number of microorganisms or their complete elimination from medical devices occurs along a spectrum, from cleaning through disinfection to sterilization. Cleaning is simply the physical removal of organic and inorganic material from devices and the surfaces of equipment. This can be accomplished by using water and detergents or enzymatic products to manually scrub and mechanically loosen the unwanted contaminating material. Cleaning may be used as a lower order process on noncritical items, but it is a mandatory step before disinfection or sterilization since the effectiveness of these higher order processes is compromised when residual inorganic or organic materials limit the active ingredients from contacting the device’s surfaces ( Figure 25–1 ). Decontamination is the process of removing pathogenic organisms from items before discarding or to make them safe to handle.
Disinfection
Disinfection can be used to eliminate most or all pathogenic micro-organisms, except bacterial spores or prions, from medical devices. Disinfection occurs across a range, from low level to high ( Table 25–1 ). The level of disinfection is determined by several factors: the type and quantity of microbial contamination; the specific germicide, including its concentration and the exposure time; the physical nature of the object; the presence of a biofilm (a tightly adherent mass of bacteria and accumulated material); and the temperature and pH of the disinfection process ( Table 25–2 ). Low level disinfection processes kill most vegetative bacteria, some fungi, and some viruses. Intermediate level disinfection kills the previously mentioned groups and most viruses and mycobacteria. High level disinfectants will eliminate all micro-organisms, except bacterial spores and prions. It is important to realize that disinfectants are chemicals and processes designed to kill micro-organisms but are intended only for application to inanimate objects. Chemicals used as disinfectants must be evaluated and cleared for medical use by the U.S. Food and Drug Administration (FDA). In contrast, antiseptics are germicides that are intended for use on living tissue, mucous membranes, or skin, and these substances are regulated by the U.S. Environmental Protection Agency (EPA).
| Most Resistant | Required Level of Disinfection or Sterilization ∗ |
|---|---|
| Prions (Creutzfeldt-Jakob disease) | Prion reprocessing |
| Bacterial spores (Bacillus atrophaeus) | Sterilization |
| Coccidia (Cryptosporidium) | |
| Mycobacteria (M. tuberculosis) | High-level disinfection |
| Nonlipid or small viruses (polio, Coxsackie) | Intermediate-level disinfection |
| Fungi (Candida, Aspergillus) | |
| Vegetative bacteria (S. aureus, P. aeruginosa) | Low-level disinfection |
| Lipid or medium-sized viruses (HIV, herpes, hepatitis B) | |
| Most susceptible |
∗ Level of disinfection or sterilization inactivates all microorganisms in the class and those classes listed below it.
| Factors | Effect |
|---|---|
| Cleaning | Failure to adequately clean an instrument results in higher bioburden, protein load, and salt concentration. These will decrease sterilization efficacy. |
| Bioburden | A larger number of microbes require a longer exposure to germicide for complete destruction. The natural bioburden of used surgical devices is 10 0 to 10 3 organisms (primarily vegetative bacteria), which is substantially below the 10 5 -10 6 spores used with biological indicators. |
| Pathogen type | Spore-forming organisms are most resistant to sterilization and are the test organisms required for FDA clearance. However, the contaminating microflora on used surgical instruments consists mainly of vegetative bacteria. |
| Protein | Residual protein decreases efficacy of sterilization. However, cleaning appears to rapidly remove protein load. |
| Salt | Residual salt decreases efficacy of sterilization more than protein load. However, cleaning appears to rapidly removal salt load. |
| Biofilm accumulation | Biofilm accumulation reduces efficacy of sterilization by impairing exposure of the sterilant to the microbial cell. |
| Lumen length | Increasing lumen length impairs sterilant penetration. May require forced flow through lumen to achieve sterilization. |
| Lumen diameter | Decreasing lumen diameter impairs sterilant penetration. May require forced flow through lumen to achieve sterilization. |
| Restricted flow | Sterilant must come into contact with microorganisms. Device designs that prevent or inhibit this contact (e.g., sharp bends, blind lumens) will decrease sterilization efficacy. |
| Device design and construction | Materials used in construction may affect compatibility with different sterilization processes and affect sterilization efficacy. Design issues (e.g., screws, hinges) will also affect sterilization efficacy. |
Sterilization
Sterilization is the process that eliminates all micro-organisms and can be performed using either physical or chemical methods. Some chemicals commonly used for high-level disinfection can also produce sterilization under specific conditions ( Table 25–3 ).
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| STERILIZATION TECHNOLOGIES |
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Disinfection of Healthcare Devices
With an understanding of the terminology of the Spaulding classification system, a matrix for appropriately processing medical equipment can be more easily understood. Critical items must be sterile and can either be purchased as sterile, single-patient use devices or may be reusable items that must be cleaned and sterilized between uses. Semicritical items must be sterile or require high-level disinfection. Most anesthesia airway equipment is considered semicritical and should undergo either high-level disinfection or sterilization. Because of the materials used and the difficulty sterilizing the long, narrow lumens, most bronchoscopes and endoscopes can only safely undergo high-level disinfection between patient use (see later discussion). Noncritical items should undergo cleaning or low level disinfection between patient use. This can be accomplished with disinfectant wipes to remove organic material including blood and secretions from external devices such as ECG cables and environmental surfaces (e.g., the work surfaces of anesthesia machines or drug carts) that may become soiled and are touched by healthcare providers.
Cleaning of equipment with detergents or enzymes is a critical part of the preparation process before disinfection or sterilization. Preferably, used items are soaked or rinsed before blood, tissue, or body substances dry on the instrument surface or in its channels ( Figure 25–1 ). Once secretions are dried, they become more difficult to remove. Although cleaning is often done by hand, there are several types of mechanical cleaning machines to automate the process.
Since they are made of materials that are stable during high temperatures, most surgical instruments undergo heat or steam sterilization. An increasing number of medical devices are made of less durable materials such as plastics and require low temperature sterilization. Traditionally, ethylene oxide gas sterilization has been used for heat-sensitive medical equipment, but more recently, many low temperature sterilization systems are available to sterilize devices that would be harmed by high temperatures. These low temperature sterilization techniques include the use of hydrogen peroxide gas plasma, peracetic acid immersion, and ozone.
The most widely used method for sterilization has been saturated steam under pressure in an autoclave ( Figure 25–2 ). Depending on the instrument being sterilized and the specific organisms that are to be eradicated, the autoclave processing cycle can be regulated by several parameters, including the amount of steam, pressure, temperature, and time. To confirm the effectiveness of the sterilization process, indicators are placed with the instruments in the autoclave.
