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Semi-critical devices pose a greater risk as they may also contact mucous membranes or non-intact skin during use. The most well-known examples are flexible gastro- intestinal endoscopes. Sterilization of semi- critical devices is preferred, but if this is not practical then high-level disinfection is considered acceptable. High-level disinfec- tants are expected to inactivate most forms of microbial life, including mycobacteria and some bacterial spores (although this may require extended time). Critical devices present the highest risk as they are intended to enter a normally ‘sterile’ area of the body, such as the bloodstream. Sterilization of these devices is required.
While heat-based disinfection and steril- ization are widely used for device process- ing, there are many instances when this is not possible. Examples include a variety of environmental surfaces and particularly devices that can be damaged by heat. In these cases chemical disinfection or ster- ilization is recommended. Some of the important guidelines and standards in the U.S. include: • CDC-HICPAC Guideline for Disinfection and Sterilization in Healthcare Facilities (2008)1
. This guideline provides a review of the methods for cleaning, disinfection and sterilization of patient-care medical devices and the healthcare environment.
• AORN Perioperative standards and recom- mended practices (2013)2
.
• ANSI/AAMI ST58 Chemical sterilization and high-level disinfection in healthcare facili- ties (2013)3
. This recommended practice, a parallel document to the widely used reference ANSI/AAMI ST79 for steam sterilization, provides detailed guidelines on high-level disinfectants, liquid chemi- cal sterilants and gaseous chemical steril- ization processes that have been cleared by the U.S. FDA for use in healthcare facilities.
It is also important to consider that chemical disinfectants and sterilization processes are registered in the U.S. by two agencies:
• Environmental Protection Agency (EPA), registers chemicals that are used on envi- ronmental surfaces.
• United States Food and Drug Administra- tion (FDA) has jurisdiction over chemicals and processes intended for medical de- vice processing.
Similar, yet often distinct, registration or licensure processes are used in other coun- tries or regions. An example for chemical sterilization are the requirements in the ANSI/AAMI/ISO 14937 standard for the characterization of a sterilizing agent and
the development, validation and routine control of a sterilization process for medical devices. It is therefore important to under- stand what specific use each type of product is intended for and to closely inspect the written instructions for use provided. They can vary significantly.
Device reprocessing The recently published recommended practice ANSI/AAMI ST58 (2013) provides up-to-date guidance on device process- ing with chemicals. It focuses on legally marketed products including high-level disinfectants, liquid chemical sterilants, and liquid chemical and gaseous sterilization processes. The terms “high-level disinfec- tion” and “sterilization” have already been described. When used appropriately, high-level disinfectants (which in the U.S. are often also labeled as liquid chemical sterilants) should be capable of rendering a device free of most pathogens, but often require significantly longer exposure times to ensure effectiveness against bacterial spores. A high-level disinfectant is essen- tially a liquid chemical sterilant, generally used for a shorter exposure time than that required to be considered a sterilant (i.e., to pass a specified spore test method). Chemi- cal sterilization is defined as using a chemi- cal agent to render a product free of viable microorganisms. Overall, these chemical products and processes utilize either the liquid (liquid chemical sterilization) or gas (gas sterilization) form of the active chem- istry. Notably ANSI/AAMI ST58 excludes consideration of gaseous chemical steriliza- tion process based on ethylene oxide, as it is the topic of a different recommended practice, ANSI/AAMI ST41.
Chemical disinfection and sterilization technologies Only a limited number of chemicals have been successfully developed for use in high- level disinfectants, sterilants and steriliza- tion processes.
These include liquid solutions (typically the active ingredient in combination with other chemicals, known as ‘formulations’) and gaseous processes (under controlled exposure conditions). The most widely used chemicals include: • glutaraldehyde solutions: 1.1-3.4% for- mulations with high-level disinfection claims ranging from 5 min (at 35C/95F) to 90 min (20C/68F). Any claims for steril- ant (sporicidal) activity typically require longer exposure times. It is important to review the specific label of each product
SELF-STUDY SERIES
prior to use, as they vary in preparation (activation) method, exposure time/tem- perature, rinsing, safety requirements, etc.
• ortho-phthaldehyde (OPA) solutions: high-level disinfectants including single use (0.05% OPA, 50-55C/122-131F for 10 min) and multiple use (0.55% OPA, 20C/68F for 12 min) formulations.
• hydrogen peroxide formulations: 2% (20C/68F for 8 min) and 7.5% (20C/68F for 30 min) for multi-use high-level dis- infection.
• a sodium hypochlorite solution created within a closed system: generates 650-675 ppm of a chlorine-based disinfectant for use at 10 min and 25C (77F).
• peracetic acid high-level disinfectant for- mulations: 0.08% (25 min) to 7% (5 min) at 25C (77C).
• a peracetic acid-based liquid chemical sterilization process, using formulated 0.2% PAA in buffered aqueous solution for 6 min at 46-60o
C (115-140o F) followed by extensively treated water rinsing.
• a specific mixture of water, alcohol and formaldehyde in a high-temperature sterilization process.
• Hydrogen peroxide gas, used for steriliza- tion processes. These may be categorized into two types: processes that contain plasma or no plasma during the process.
• Humidified ozone gas, used in a low- temperature sterilization process. It is important to remember that these products and processes can vary sig- nificantly in product claims as well as use requirements such as exposure times, rinse times (for liquid products to remove toxic substances following disinfection), stability (e.g., single or multiple use), device restric- tions, etc. Therefore, care should be taken to review in detail the manufacturer’s written instructions regarding the safe and effec- tive use of these technologies. In addition, it is important to check that the product or process is applicable for your particular intended use; for example, a list of U.S.- FDA cleared sterilants and high-level dis- infectants for processing reusable medical/ dental devices is maintained by the FDA at:
http://www.fda.gov/MedicalDevices/ DeviceRegulationandGuidance/Reprocess- ingofSingle-UseDevices/
ucm133514.htm.
In preparation ANSI/AAMI ST58 provides guidance on the full processing cycle, which starts with the safe handling of devices through transportation to a defined area where pro- cessing can occur. Although this can be in a defined, centralized sterilization depart-
See SELF-STUDY SERIES on page 52
www.hpnonline.com • HEALTHCARE PURCHASING NEWS • March 2014 51
Self-Study Test Answers: 1. D, 2. A, 3. D, 4. A, 5. D, 6. E, 7. C, 8. G, 9. E, 10. G
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