Definitions

Cleaning is a term that is both simple to understand and difficult to define precisely in terms of a measurable endpoint. The official definition of cleaning used by the FDA is “the removal, usually with detergent and water, of adherent visible soil, blood, protein substances, and other debris from the surfaces, crevices, serrations, joints, and lumens of instruments, devices, and equipment by a manual or mechanical process that prepares the items for safe handling and/or further decontamination.”¹⁰ Although this definition seems straightforward, there is as yet no uniform consensus on how this process is operationally defined or what the endpoint of the process should be. How hot should the water be, and what concentration of detergent should be used? How many times should the cleaning brush be passed down the endoscope channels? What does “visibly clean” mean, and how can this be applied to the internal channels of an endoscope that cannot be examined? Many experimental methods can be used to determine the efficacy of cleaning by the detection of residual protein, carbohydrate, blood, or viral or bacterial RNA or DNA,^11–16 although these are impractical for routine clinical use.

Despite the difficulty in precisely defining the process or the subsequent endpoint, there is ample evidence that endoscope cleaning (as currently performed) is an essential part of the disinfection process. Mechanical cleaning alone reduces microbial counts by approximately 10³–10⁶ (three to six logs), or a 99.9% to 99.9999% reduction.^17–24 Cleaning is an integral part of any endoscope reprocessing regimen because failure to clean endoscopes or their accessories adequately can defeat disinfection or sterilization processes.²⁵

Antiseptics are chemicals intended to reduce or destroy microorganisms on living tissue (e.g., skin), as opposed to disinfectants, which are used on inanimate objects (e.g., medical devices such as endoscopes). Disinfection is defined broadly as the destruction of pathogenic and other types of microorganisms. There are three levels of disinfection, as follows:

For liquid chemical germicides (LCGs), high-level disinfection is operationally defined as the ability to kill 10⁶ mycobacteria (a six-log reduction). The FDA defines a high-level disinfectant as a sterilant that is used for a shorter contact time.²⁶ This difference in the way the same chemical is used to achieve different levels of disinfection and sterilization is important for endoscopy because the contact times for sterilization with any given LCG are generally much longer (hours) than for high-level disinfection (minutes) and may be detrimental to the endoscope. The relative resistance of various microorganisms to LCGs is shown in Box 4.1.

Sterilization is the destruction or inactivation of all microorganisms, or the absence of all microbial life. As an endpoint, it is an absolute (sterile or not sterile). The process is operationally defined as a 12-log reduction of bacterial endospores.²⁷ Not all sterilization processes are alike, however. Steam and dry heat are the most extensively characterized processes; both are thermal methods that do not require the same physical contact as LCGs to achieve sterilization, and the processes are routinely monitored by the use of biologic indicators (e.g., spore test strips) to show that sterilization has been achieved. Although theoretically sterilization could be achieved with LCGs, the FDA and other authorities have stated that these processes do not convey the same sterility assurance as other sterilization methods.^26,28,29

The Spaulding classification system divides medical devices into categories based on the risk of infection involved with their use.^30,31 With some modifications, this classification scheme is widely accepted nationally and internationally and has been used by the FDA, the Centers for Disease Control and Prevention (CDC), epidemiologists, microbiologists, and professional medical organizations to determine the degree of disinfection or sterilization needed for various medical instruments. Three categories of medical devices and their associated level of disinfection are recognized, as follows:

Disinfection and Gastrointestinal Endoscopy

GI endoscopes are considered semicritical devices and should undergo at least high-level disinfection. This standard has been endorsed by the FDA³²; the CDC³³; and numerous professional medical organizations, including the American Society for Gastrointestinal Endoscopy (ASGE), the American College of Gastroenterology (ACG), the American Gastroenterology Association (AGA), the Society of Gastroenterology Nurses and Associates (SGNA), the Association of Perioperative Registered Nurses (AORN), the Association for Professionals in Infection Control and Epidemiology (APIC), and the American Society for Testing and Materials (ASTM).^34–37 Because of design considerations, GI endoscopes can be a challenge to clean and disinfect. Endoscopes are heat-labile instruments and cannot be steam autoclaved. They possess several long, narrow internal channels with bends (Fig. 4.1) that require exposure to the LCG to achieve high-level disinfection. Generally, the air and water channels are too narrow to allow the passage of a cleaning brush (although the LCG is routinely circulated through this channel); however, one manufacturer has designed an endoscope with air and water channels that can be brushed.³⁸ Despite the complex internal design, high-level disinfection is not difficult to achieve with rigorous adherence to currently accepted guidelines. Most accessory instruments used during endoscopy either contact the bloodstream (e.g., biopsy forceps, snares, and sphincterotomes) or enter sterile tissue spaces (e.g., biliary tract) and are classified as critical devices. As such, these devices require sterilization.

Fig. 4.1 Schematic of internal channels of an endoscope.

(Adapted from Olympus America.

Most accessories used during GI endoscopy are labeled by the FDA for single use (i.e., disposable) and are intended to be discarded at the end of the procedure. Because these items are sterilized by the manufacturer, reprocessing is not an issue. However, some accessories are designed to be resterilized and reused and are designated as such by FDA. In this case, cleaning and sterilization is performed by the user according to the manufacturer’s instructions. The issue of sterilization of endoscopic accessories becomes considerably more complex when the reuse of single-use devices (SUDs) is considered. Although labeled for single use (disposable), many hospitals safely clean, resterilize, and reuse SUDs, resulting in decreased costs and reduced medical waste generation.^39–42 Despite the absence of evidence suggesting that this practice resulted in patient injury, the FDA issued a guidance document on August 14, 2000, that altered the agency’s regulatory policy. The FDA considered the process of reprocessing (i.e., cleaning and sterilizing) a used SUD into a ready-for-patient-use device as “manufacturing,” and as a result hospitals or third-party reprocessing companies that reprocessed SUDs were required to follow the same regulations as the original equipment manufacturers: premarket notification and approval requirements, including 510(k) and premarket approval application (PMA); registration and listing; submission of adverse event reports; manufacturing and labeling requirements; tracking of devices; and correcting or removing from the market unsafe medical devices. Enforcement of these regulations was phased in over the subsequent 18 months (all aspects taking effect by February 14, 2002). The most onerous requirement was that a 510(k) or PMA was needed for each device that the institution intended to reprocess (both manufacturer and model-specific).⁴³ The regulatory burden imposed by these requirements essentially eliminated the practice of reprocessing of SUDs by most hospitals.

Risks of Inadequate Disinfection

Before discussing the specifics of current guidelines for endoscope cleaning and disinfection, it is helpful to understand how guidelines evolved over time in response to episodes of infection to minimize or eliminate vulnerabilities in the reprocessing procedure. Initially, endoscopes were simply washed with tap water and detergent, followed by exposure to alcohol.⁴⁴ In the 1970s, centers began using various “disinfectants” to reprocess endoscopes.^45–52 The germicides used were generally antiseptic agents. Many of the agents that were considered to be effective at that time (e.g., alcohols, phenolics, iodophors, quaternary ammonium compounds, and chlorhexidine) have since been shown to be inadequate for high-level disinfection of GI endoscopes (Table 4.1).⁵³

Table 4.1 Pathogens Reportedly Transmitted during Gastrointestinal Endoscopy

AER, automatic endoscope reprocessor; LCG, liquid chemical germicide.

From Nelson DB: Infectious disease complications of GI endoscopy. Part II. Exogenous infections. Gastrointest Endosc 57:695–711, 2003, with permission from the American Society for Gastrointestinal Endoscopy.

To standardize the cleaning and disinfection process, the ASGE, the AGA, and the ACG published joint guidelines on endoscope reprocessing in 1988. Key components of these guidelines were the emphasis on thorough manual cleaning of the instrument and all channels, high-level disinfection with an approved LCG (with a 10-minute exposure for glutaraldehyde specified at that time), a water rinse to remove residual sterilant, and a final drying step with forced air. The handles of nonimmersible endoscopes were to be cleaned with alcohol.⁵⁴ The British Society of Gastroenterology (BSG) published similar guidelines the same year, although notable differences included a recommended exposure time for glutaraldehyde of 4 minutes, the use of quaternary ammonium detergents as an acceptable second-line disinfectant, and only a brief mention of drying.⁵⁵ One of the authors of the BSG guidelines interpreted the guidelines as applying only to the insertion tube (which had direct patient contact) rather than to the entire endoscope (particularly the control handpiece, which was not high-level disinfected) and recommended that if the handpiece was “extensively contaminated,” or if the next patient was known to be immunocompromised, only then was high-level disinfection of the entire instrument necessary. If the instrument was not submersible, cleaning with alcohol and chlorhexidine was “practical.”⁵⁶

More recent guidelines in the United States from multiple organizations have been uniformly consistent (all endorsing a 20-minute exposure to glutaraldehyde at room temperature).^34–3657