medical device can include an instrument, apparatus, implement, machine, appliance, implant, reagent for in vitro use, software, material or other similar or related article, intended by the manufacturer to be used, alone or in combination, for medical purpose(s). These can include the diagnosis, prevention, monitoring, treatment or alleviation of disease, compensation for an injury, the investigation, replacement, modification, or support of the anatomy or of a physiological process, for supporting or sustaining life, in the control of conception, for the disinfection or sterilization of medical devices, and providing information by means of examination of specimens derived from the human body.1
Legally, products that may be medical devices in some jurisdictions but not in others can include disinfection substances, aids for persons with disabilities, devices incorporating animal and/or human tissue, and devices for in vitro fertilization or assisted reproduction technologies. A reusable medical device is a device that has been designated by the device manufacturer as suitable for processing and reuse. As they are used, they can become contaminated, and processing must ensure that the devices are rendered safe for the next patient use. Effective processing can include cleaning, disinfection, inspection and maintenance, and sterilization between patient use and is important to prevent adverse patient effects, particularly health care acquired infections (HAIs). In addition to medical devices, a variety of other surfaces can be contaminated in clinical practice, and these are also be subjected to routine processing to reduce the risks of pathogen transmission. Health care facility environments are known to be sources of pathogens such as methicillin-resistant Staphylococcus aureus
(MRSA), Clostridium difficile
, vancomycin-resistant enterococci, and other pathogenic organisms.2
These organisms have been isolated from surfaces frequently contacted by health care personnel or patient intact skin but regardless can lead to cross-contamination and infection.
The purpose of this chapter is to describe the risk classification of medical and surgical devices, determine the proper steps for processing, supporting validations to be performed to confirm the effectiveness of those steps, and current standards and guidance documents that apply. The types of processing that is appropriate for different device types is considered as well as what a manufacturer needs to do to ensure those processing steps are appropriate.
PROCESSING OF MEDICAL DEVICES
The definition of processing is the steps performed between patient use and the activities to prepare a new or used device for its intended use. A “processor” may be an organization and/or individual with the responsibility for carrying out actions necessary to prepare a new or reusable device for its intended use. Processing devices can range from just cleaning for some noncritical devices or surfaces to a full cycle of cleaning, disinfecting, and terminal sterilization for semicritical and critical devices. These processes are explained in detail later in this chapter. Figure 47.1
shows the typical processing cycle of devices as can occur in a health care facility or center.
The important steps of processing medical devices in a health care facility, depending on their risk criticality, can include
Precleaning to prevent soil from drying on devices, making it easier to clean and to ensure safe transport, reducing risk to staff or others that may be at risk of contacting the devices
Transport to a central processing area in which devices should be kept moist in a container by adding a towel moistened with water. Appropriate foam-, spray-, or gel-based products may also be used.
FIGURE 47.1 The typical processing cycle for reusable medical devices. The full cycle is typical for critical (eg, surgical) devices, with acceptable steps indicated for semicritical and noncritical devices.
Disassembly, sorting, and cleaning pretreatment that can include rinsing, soaking, and brushing
Thorough cleaning by manual or automated methods. This includes thorough rinsing and drying.
Terminal disinfection or sterilization according to the Spaulding classification (see in the following text) or other specific, local regulatory requirements
Low-, intermediate-, or high-level disinfection using physical (eg, heat) or chemical processes
Sterilization by processes using steam or gases such as vaporized hydrogen peroxide
Appropriate packaging of devices for terminal disinfection or sterilization, if applicable
Appropriate storage until subsequent use
Cleaning is of particular concern, and there are many factors that affect the efficacy of the cleaning processes. These include the following3
Amount and type of soil (contamination on a device following its use) present on the device can affect the effectiveness of cleaning chemicals and sterilants used because they may become diluted or ineffective in the presence of soils.
Water quality and temperature as cleaning chemicals are designed to be optimally effective at specific temperatures and water hardness (concentration of calcium and magnesium ions in water) can alter the effectiveness of cleaning.
Availability and use of cleaning chemicals, for example, if specific cleaning chemicals recommended to be used are not available, can alternatives be used?
It is essential that the staff performing the processing are trained and competent in the use of all equipment, chemicals, and accessories to adequately clean each device (eg, lumens and other hard to access areas, disassembly, and reassembly of items).
Rinsing of the devices ensures that no harmful residuals (from soil or the cleaning process) remain on the device that can interfere with subsequent processing or patient use.
One important aspect of processing medical devices is to have a quality management system at the facility responsible for processing. This includes the requirements for
Documentation and document maintenance for the appropriate time period
Infection prevention and control
Education and training
Personal protective equipment (PPE) requirements specific for each process performed
Automated washer or washer-disinfector, disinfectant, and sterilizer monitoring (eg, biological and chemical indicator controls) and preventative maintenance procedures
Key parameter monitoring (eg, temperature, exposure time, concentration) to ensure that the processed device has met the validated process parameters
Traceability to ensure the ability to track back to a patient from the devices and appropriate processing steps conducted in the event of a device recall or investigation of an adverse patient event
HUMAN FACTORS ISSUES
The incidence of hospital-acquired infections (HAIs) is a concern throughout the world. They have heightened regulatory attention on reusable devices, with impacts on manufacturers and health care users of these devices. Reusable devices must be designed to be cleaned, disinfected, and sterilized, when appropriate, between patient use. Manufacturers are expected to design devices and perform associated validations to ensure that the devices can be processed at health care facilities and publish clear procedures in their instructions for use (IFU) that are easy for health care personnel to follow. Health care personnel should also carefully follow the manufacturer’s instructions. Correct processing of medical devices plays an important role in the prevention of HAIs. Many cases of inappropriate cleaning, disinfection, or sterilization of medical devices have been identified as causes of HAIs or other adverse patient reports. Other concerns such as epidemics and increasing prevalence of antimicrobial resistance has intensified resources and improved practices to strengthen infection prevention strategies in health care facilities.
Human factor safety margins should be built into design and instructions to better manage device safety in the health care setting. Considerations include the complexity of device design, accuracy of validated processing instructions, and the practical use of instructions in health care facilities. Common human factor consideration practices can include4
Processing instructions that are clear, legible, and written in a step-by-step manner (chronological) from the initial processing step through to the terminal processing step and storage requirements
Instructions written in simple and clear language
The use of charts, pictures, or diagrams that provide visual aids for processing steps
Specific instructions for known risk areas due to the design of the device, for example, difficult to clean locations
Visual inspection procedures following the cleaning processes
The ability to clean a medical device should be considered early in the initial device design and engineering planning. Features that effectively facilitate processing (eg, the design of flushing ports for internal device areas or the ease of device disassembly) should be incorporated when designing a reusable medical device. This has a significant impact on the ability of health care personnel to effectively clean the device, which correlates directly to patient safety. Human factors in medical device processing can be as minor as a simple variation in a cleaning step. For example, health care facility personnel may scrub laterally instead of the recommended circular motion to ensure proper cleaning. Manufacturers may also need to be aware that some health care facilities have elected to develop facility-specific cleaning processes instead of following device manufacturer’s validated cleaning instructions that may be unpractical or less efficient.
Health care facility processing personnel must be properly trained to follow manufacturer’s written cleaning instructions but then also assessed to show competency in following those instructions. If instructions and department requirements are not followed, the subsequent patient that comes into contact with that device is at risk for developing a HAI or other complication. A notable example of this has been highlighted by outbreaks
of HAIs following the use of contaminated flexible endoscopes.5
In a recent safety communication, the US Food and Drug Administration (FDA) noted that “although the complex designs of duodenoscopes improves the efficiency and effectiveness of endoscopic retrograde cholangiopancreatography (ERCP), it causes challenges for cleaning and high-level disinfection. Some parts of the scope may be extremely difficult to access and effective cleaning of all areas of the duodenoscope may not be possible.” In addition, a recent FDA engineering assessment and a growing body of literature have identified design issues in duodenoscopes that complicate processing of these devices. For example, one step of the manual cleaning instructions in the device labeling is to brush the elevator area at the patient insertion end of these devices; however, the moving parts of the elevator mechanism contain microscopic crevices that may not be easily reached with a brush. Residual body fluids and organic debris may remain in these crevices after cleaning and disinfection. If these fluids contain microbial contamination, subsequent patients may be at risk of serious infection development.10
The ability of health care personnel to be able to practically follow the IFU should be considered. A US FDA guidance recommends in-use testing to verify that medical devices can be adequately cleaned after patient contact in a health care facility.4
First, the contaminants present on the device during patient procedures should be identified and understood. Next, the devices determined to have the greatest cleaning challenges should be subjected to a worst-case contamination challenge. Complex invasive devices that have a clear potential for serious harm resulting from use errors should be particularly considered for human factors. Identification of such risk design can be based on investigation of medical device adverse reports and recall information, such as those in the United States.12
Human factor data may need to be considered in developing and submitting instructions for processing for regulatory approval, unless the submission does not involve any changes to users, user tasks, user interface, or use environments from those of predicates. These devices can include but may not be limited to4
ablation generators (associated with ablation systems)
artificial pancreas systems
automated external defibrillators
duodenoscopes with elevator channels
gastroenterology-urology endoscopic ultrasound systems with elevator channels
hemodialysis and peritoneal dialysis systems
implanted infusion pumps
insulin delivery systems
negative-pressure wound therapy intended for use in the home
robotic catheter manipulation systems
robotic surgery devices
ventricular assisted devices
Classroom training for health care personnel can be important to educate personnel on how to appropriately clean, inspect, and further process devices during in-use testing. During this exercise, the manufacturer solicits feedback from the trainees about the ease of use of the processing instructions. This training can aid the manufacturer in understanding how their processing instructions are being interpreted in a health care facility setting. Depending on the feedback, the manufacturers may adjust the processing instructions if any issues with usability are identified.
Overall, human factor analysis related to health care processing of medical devices is a valuable component during product development of medical devices. In-use testing can be a powerful method to ensure health care personnel can appropriately follow and perform all of the processing steps. This is an integral part of ensuring the device can be processed properly between patient use. Manufacturers are recommended to use similar methods, terminology, and document layout to aid health care personnel in the comprehension and adherence to the instructions. The processing instructions for a device should be validated to ensure health care personnel will be able to understand and follow the processes. This can include observing and documenting participants while performing the cleaning and subsequent processing steps as well as asking if the instructions are feasible or at all difficult. This information should be documented, and changes to the instructions should be made if appropriate.
Dr E. H. Spaulding originally categorized reusable medical devices into four groups: critical, semicritical, noncritical, and nonpatient contacting surfaces.13
These categories have been essentially accepted worldwide, are endorsed by many regulatory agencies including in the United States by the Centers for Disease Control and Prevention (CDC) and FDA and are commonly used today. These classifications are used to specify what level of disinfection or sterilization is appropriate for the device, depending on the risk to the patient; however, it is important to note that thorough cleaning of the device is typically required prior to any terminal disinfection and sterilization processes.
Critical devices have a substantial risk of transmitting infection if the item is contaminated with microorganisms at the time of use. These are devices that are introduced directly into the body, either into or in contact with the bloodstream or other sterile areas of the body. Examples include needles, scalpels, transfer forceps, cardiac catheters, implants, and the inner surface components of extracorporeal blood-flow devices such as
of the heart-lung oxygenator and the blood side of artificial kidneys (hemodialyzers). These items must be, at a minimum, cleaned and then sterilized between patients.
Devices classified as semicritical come in contact with mucous membranes (that can be naturally contaminated with microorganisms) but do not ordinarily penetrate body surfaces. Examples of these devices are many types of flexible fiber-optic endoscopes, endotracheal and aspirator tubes, bronchoscopes, laryngoscopes, respiratory therapy equipment, vaginal specula, and some urinary catheters. These devices are recommended to be cleaned and preferably sterilized, although high-level disinfection is acceptable at a minimum. If sterilization is not an option, treatment with a broad-spectrum chemical disinfectant that labeled with a tuberculocidal claim (a high-level disinfectant) may be used.
Noncritical devices usually come into direct contact with the patient but, in most instances, only with intact skin. Such items include facemasks, blood pressure cuffs, and most neurologic or cardiac diagnostic electrodes. Use of these devices carry a relatively lower risk of transmitting infection directly to patients but can be a source of microbial transmission. These devices are processed by cleaning and may require low- to intermediate-level disinfection.
The category that carries the least risk of disease transmission is nonpatient contacting surfaces. These surfaces potentially contribute to secondary cross-contamination such as by the hands of health care personnel that will subsequently come into contact with patients. Examples of these devices are medical equipment surfaces, such as frequently touched adjustment knobs or handles on hemodialysis machines, instrument carts, or dental units. These devices are often recommended to be processed by cleaning and may also benefit from periodic low- to intermediate-level disinfection. A wide range of disinfectants may therefore be used.
FIGURE 47.2 General resistance of microorganisms to disinfection and sterilization.
Microorganisms vary widely in their resistance to physical and chemical disinfection and sterilization methods (see chapter 3
). The types of microorganisms that are present on medical items or surgical materials following patient use can have a significant effect on the desired effectiveness of disinfection or sterilization. The most resistant types of microorganisms are generally regarded to be bacterial spores, some of which are significantly more resistant to both chemical and physical stresses than a wide variety of other microorganisms.14
In a broad descending order of relative resistance, considerably below that of bacterial endospores are considered mycobacteria species (eg, Mycobacterium tuberculosis
). Following that, in descending order of resistance, are small nonlipid viruses, the vegetative and spore forms of fungi, vegetative bacteria, and medium-sized or lipid-containing viruses (Figure 47.2
). This hierarchy is useful in determining the appropriate level of disinfection or sterilization process that needs to
occur after the cleaning process and before the next patient use.17
This hierarchy is also important in determining the correct level of terminal disinfection or sterilization recommended to be appropriate (Table 47.1
TABLE 47.1 Level of disinfection or sterilization appropriate to kill microorganisms
Level of Disinfection or Sterilization
Prions (eg, causative agent in Creutzfeldt-Jakob disease)
Bacterial spores (eg, Bacillus subtilis, Clostridium difficile)
Mycobacteria (eg, Mycobacterium tuberculosis)
Nonlipid or small viruses (eg, poliovirus, rhinovirus)
Fungi (eg, Cryptococcus neoformans, Candida albicans)
Vegetative bacteria (eg, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus)
Lipid or medium-sized viruses (eg, herpes simplex, hepatitis B)
a Unique processing recommendations (see chapter 68).
Examples of notable pathogens that produce bacterial spores include Bacillus cereus
, Clostridium botulinum
, and C difficile
. M tuberculosis
and nontuberculous mycobacteria are frequently associated with heath case-associated transmission, including cases due to inappropriately cleaned, disinfected, and sterilized device. Examples of fungal pathogens include Candida albicans
and Aspergillus fumigatus
. Important pathogenic gram-negative bacteria include Pseudomonas aeruginosa
, Klebsiella pneumoniae
, and Salmonella
species. P aeruginosa
is known for its preference for moist environments and its propensity to form biofilms that are difficult to remove or inactivate (see chapter 67
species are found to be common microorganisms associated with gastrointestinal (GI) endoscopy procedures. Outbreaks with these bacteria are often related to inappropriate use of disinfectants that did not meet the criteria of high-level disinfection. Examples of gram-positive bacteria include S aureus
and Streptococcus pyogenes
. Finally, enveloped viruses including key blood-borne pathogens such as HIV and hepatitis B viruses (HBVs).
CLINICAL CONTAMINANTS ON MEDICAL DEVICES
Even though critical and semicritical devices are often considered to present the greatest challenge to cleaning, disinfection, and sterilization with the amount of contaminants following clinical use and associated patient risks following processing, noncritical devices and surfaces also need to be cleaned and disinfected properly. Clinical contaminants found on medical devices directly relate to the surgical procedure in which they are used or the environment the device or surface is located. Noncritical devices and surfaces can be contaminated with a variety of soils including patient materials and microorganisms, including notable pathogens often associated with outbreaks such as C difficile
, noroviruses, MSRA, etc. A recent review on the role of the patient environment in the transmission of microorganisms, in particular multidrug-resistant organisms, highlighted that the role of the environment in the acquisition of HAIs are underestimated.19
New techniques and technologies may be used to reduce these risks such as improving manual chemical disinfection, the use of automated environmental disinfection methods (eg, ultraviolet [UV] and hydrogen peroxide gas), environmental monitoring, molecular detection methods, and self-disinfecting surfaces.19
The clinical contaminants that can be present on devices following patient use include organic and inorganic materials. Organic materials include blood, mucus, urine, tissue, carbohydrates, fats, protein, and microorganisms (such as bacteria, virus, and fungi). Inorganic materials can include salts, metals, calcium deposits, and iodine or chlorhexidine (eg, from antiseptics use during surgery). Studies on the biochemical nature of contaminants following surgical use of devices found that the levels of visible contamination can range considerably, as did the quantitative levels of contaminants, including detectable microorganisms.20
This is important to note that many of these contaminants may inhibit the activity of subsequent disinfection or sterilization processes and, if present following processing, may also lead to toxic reactions in patients or device damage. High levels of total organic carbon (TOC), protein, and hemoglobin were observed on many device types indicating how important processing is between patient use.19
Overall, the levels of microorganisms on surgically used devices were actually low (<600 detectable colony-forming units [CFUs]).20
Another study showed that surgical devices used in sterile body cavity procedures have relatively low bioburden levels, averaging about 102
per device when compared with devices used in nonsterile body areas (eg, GI endoscopes), which are in the range of 105
These results would suggest that the microbial challenge may actually be greater on many of the semicritical devices in comparison to critical devices. In a study that tested 50 surgical instruments obtained from 25 surgical procedures, 30% of the devices resulted in no growth, 14% resulted in 11 to 100 CFUs, and 14% resulted in greater than 100 CFUs.22
Two devices had higher levels of bacterial growth and both were contaminating with coagulase-negative Staphylococcus
, a normal part of the skin flora.
Any contaminating soil (such as blood, mucus, or feces) remaining on a device after the cleaning process
may contribute to the failure of a disinfection or sterilization process. The clinical soil may prevent penetration to microorganisms and may inactivate disinfectant chemicals such as chlorine, iodine, oxidizing agents, and quaternary ammonium compounds. This effect can be a greater concern when lower concentrations of biocides are used and with low-level disinfectants compared to higher concentrations or more potent, high-level disinfectants. In addition, this factor underscores the necessity and importance of thoroughly cleaning a medical device prior to chemical disinfection or sterilization. An example of this was reported in an outbreak of septicemia caused by a Serratia
species from a flexible fiber-optic endoscope.23
This device had been sterilized in an ethylene oxide (EO) gas process but had not been cleaned properly before the sterilization cycle. This testing and other research has shown that even a rigorous cycle capable of killing all microorganisms, including bacterial spores, may not kill even relatively sensitive vegetative bacterial cells if they are protected by extraneous organic material. This observation may also be intimately associated with the number of microorganisms present. Effective cleaning procedures that remove organic soil simultaneously tend to lower the general level of microbial contamination associated with the soil by physical removal alone and increase the effectiveness of the subsequent antimicrobial process.
Because the presence of microbial pathogens are assumed to be present as biohazards on contaminated devices, specialized protective equipment for the eyes, face, head, and extremities (eg, masks, gloves, goggles, face shields, and gowns) are appropriate, particularly during the handling and cleaning of devices prior to an antimicrobial process. Protective clothing, respiratory devices, and protective shields and barriers have been designed to protect the wearer from injury. The PPE is used by health care personnel and others whenever necessary to protect from such hazards and reduce the risks of injury or impairment in the function of any part of the body through absorption, inhalation, or physical contact.
Cleaning is the first and most important step of processing. The formal definition in regard to processing medical devices is the removal of contaminants to the extent necessary for further processing or for intended use.1
Cleaning consists of the removal, usually with a detergent-based formulation and water, of clinical soil (eg, blood, protein substances, and other debris) from the surfaces, crevices, serrations, joints, and lumens of a medical device by a manual and/or automated process that prepares the devices for safe handling and/or further processing. The goals of these processes are to remove microbiological and chemical (organic and inorganic materials) contaminants. These processes include the use of various cleaning (detergent-based) chemistries with water combined with various brushing, flushing, soaking, and rinsing steps. Cleaning can be performed manually, by wiping and immersion in a sink or basin, or by using automated systems such as ultrasonic cleaning systems and automated washers or washer-disinfectors.
For many devices, precleaning moistens and loosens gross clinical soil and makes the subsequent cleaning steps more efficient. This should be performed as soon as possible after devices have been used and most often includes just the use of water. Other chemicals that may be available in surgical or clinical practice (eg, antiseptics and saline solutions) should be avoided due to the potential for device damage and other complications. Close attention to rinsing devices at this stage can reduce the gross clinical soil load in the subsequent cleaning steps. Manual cleaning in many countries is the most widely used method performed to thoroughly clean devices using a variety of methods such as immersion, wiping, brushing, and flushing. If a device is able to go through an automated process, this method is preferred and is often conducted in addition to manual cleaning steps when appropriate. This allows minimal handling of contaminated devices and allows for larger processing capacity. The automated process, such as in washer-disinfectors, combines cleaning with disinfection (and often drying) to allow devices to be safely used or handled for packaging depending on the terminal antimicrobial process applicable. The steps for a manual cleaning may typically include
Prerinsing to remove soil
Washing with a detergent-based formulation diluted according to manufacturer’s recommendations and at the appropriate water temperature
Soaking, brushing, and flushing (as applicable for the device type)
Rinsing to remove any remnants of soil and cleaning chemistries
Manual disinfection and/or drying as appropriate
The steps for a manual cleaning with the use of ultrasonics can include
Prerinsing to remove soil
Washing with a detergent-based solution diluted according to manufacturer’s recommendations and used at the appropriate water temperature
Soaking, brushing, and flushing (as applicable for the device type)
Cleaning in an ultrasonic washer at a given power frequency (eg, >38 kHz) and time, which will typically be conducted in a detergent-based solution
Rinsing to remove any remnants of soil and cleaning chemistries
Manual disinfection and/or drying as appropriate
Note that during these cleaning processes, it is important to consider parameters for efficient cleaning, including time, temperature, type(s) of cleaning agent(s), and
water quality specifications. The steps for an automated cleaning may include
Prerinsing to remove soil
Detailed manual washing of certain device features (if appropriate) with a detergent-based solution diluted according to manufacturer’s recommendations and at the appropriate water temperature. This may include soaking, brushing, moving, and flushing of device features.
Rinsing to remove any remnants of soil and cleaning chemistries
Processing in a mechanical washer-disinfector compliant with International Organization for Standardization (ISO) 15883-1 with a defined, validated cycle.24
The automated cycle may include the following cleaning cycle parameters
These parameters also include requirements to meet time, temperature, type(s) of cleaning agent(s), and water quality specifications.
Automated washer-disinfectors may also include validated disinfection and drying phases of cycles, such as thermal or chemical disinfection, purging, and hot air drying.
The final results from the cleaning process must result in a visually clean device, a device that meets the appropriate low amounts of organic soil and microbial load, is not cytotoxic, and must be fully functioning for the next patient use or further processing (eg, packaging and sterilization).
The determination of the appropriate type of detergent(s) used in the cleaning processes is an important part of the cleaning process. Considerations include appropriate labeling with the detergent product (eg, safe for use on medical devices), material compatibility, tolerance of water quality being used during cleaning, types of processing methods that can be used, temperature and contact times, and even in some cases environmental safety requirements. Currently, there are no specific regulatory requirements to determine the effectiveness or specifications for such detergent formulations. But the characteristics of an ideal cleaning agent can include nonabrasiveness, low foaming, free rinsing, biodegradable, able to rapidly dissolve/disperse various types of soil (lipids, proteins, etc), nontoxic, effective in the presence of varying water quality, have an acceptable shelf life, and be cost effective.24
Cleaning chemistries are typically classified by the type of active chemistry present such as acidic, alkaline, and enzymatic (although these can often be combined). Acidic cleaners are commonly more effective at removing mineral (inorganic) deposits and, when appropriately used, can also allow for oxidation to protect certain types of material surfaces, such as stainless steel. Certain types of formulated enzymatic and acidic cleaners are also better for removing certain types of starches, carbonates, and insoluble hydroxides from surfaces. Alkaline cleaners are very effective at breaking down and removing various organic materials such as patient soil components (eg, blood, proteins, hemoglobin). Alkaline cleaners can remove oils, fats, greases, proteins, and an array of other soils. For medical device cleaning, the most widely used cleaning chemistry formulations are enzymatic (which can be alkaline or acidic in formulation), neutral detergent cleaners, and mild to strong alkaline cleaners, or combinations of these. In some cases, combinations of an alkaline cleaner followed by an acidic (or neutralizing) cleaner are used in different phases of a cleaning cycle. Enzymatic detergents often have the benefit of being in the neutral pH range (pH 6-8), with enzymes added to enable soil component breakdown, and classically demonstrate the greatest compatibility on surfaces, depending on the detergent formulation. The different types of enzymes that may be added in these products can include
Proteases that break down many proteins contained in blood and saliva
Amylases that target starches and certain carbohydrates
Lipases that break down certain types of fats and lipids
Cellulases, which are active against certain types of fibers and may even be useful against certain types of biofilms
Overall, the effectiveness of enzymatic-based detergents depends on the enzymes included, as well as the other components in the formulation (eg, buffers, surfactants), and the correct use in accordance with manufacturer’s instructions. Acidic and alkaline-based products, in general, can be equally effective cleaning chemistries, when used correctly but may also be more aggressive on device surfaces over repeated use. Overall, the cleaning abilities and device compatibility profiles can vary considerably based on the individual product formulations.
The benefits of lubrication include easing stiffness, prolonging instrument life, and reducing the risk of rust, tarnish, and corrosion damage. The typical recommendation is to add lubrication to the appropriate device after the cleaning and drying steps (eg, prior to sterilization or clinical use). Lubricants should be used in accordance with their manufacturer’s instructions and only on devices requiring lubrication.
Equipment Used in Cleaning
A variety of accessories can be used for manual cleaning. Example of these accessories are brushes of many shapes and sizes that are specified by the size and length or by a part number. Brushes are an integral part of cleaning various types of device crevices, surfaces, and lumens. It is particularly important to use the appropriate-sized brush for cleaning device lumens to ensure cleaning and reduce the risk of damage to the inside of the lumen. ISO 17664 states that the requirements for brushes and all of the accessories required need to be included in the cleaning steps in the IFU.1
A variety of other cleaning accessories include cloths and sponges as well as specific aids to safely remove certain types of stubborn soils (such as cements and cauterized blood) if present. It is important to note that most manufacturers recommend against the use of accessories such as scouring pads due to potential damage to device surfaces over time.
Ultrasonic cleaning equipment provides a sonication process to aid in the cleaning process while the device is immersed in a low-foaming detergent solution. Sonication is a process using ultrasonic waves, which cause the disruption and removal of soil from surfaces by the effect of cavitation. Cavitation is a process where microbubbles are produced in the presence of sonication and implode on contact with surfaces to dislodge soil from the device surfaces. Because ultrasonic cleaning is especially effective in removing soil and other debris from hard-to-reach areas, it is usually a necessary step for complex devices.25
Automated washers and washer-disinfectors are designed to clean and disinfect (when applicable) a large range of devices. These are computerized processes that are programmed for cleaning, disinfection, and most often drying. There are many different types, sizes, and processes available. ISO 15883-1 describes the central design and performance criteria for such equipment, including cleaning, disinfection, and drying requirements.24
The next steps after cleaning are appropriate disinfection and/or sterilization. Disinfection may be an intermediary step between cleaning and sterilization to render devices safe for handling during inspection and packaging or it may be the terminal step of processing, depending on the classification and intended use of the device. Disinfection is the process to reduce the number of viable microorganisms to a level specified as being appropriate for a defined purpose. High-level disinfection is a process that is expected to kill all microorganisms but not necessarily large numbers of bacterial spores (see Figure 47.2
) and is often recommended during the processing of critical device (prior to packaging and sterilization) or the terminal processing of semicritical devices. Intermediate-level disinfection is a process that is expected to kill most viruses, fungi, vegetative bacteria, and some mycobacteria but not typically fungal or bacterial spores. Low-level disinfection is a process that should inactivate most vegetative bacteria, some viruses, and some fungi but not mycobacteria or fungal and bacterial spores.26
These terms are widely used in certain parts of the world, such as in the United States, but may not be widely used or defined in other areas (see chapter 2
There are many methods of disinfection depending on the device type, but these can be generally divided into two major types, high-temperature or low-temperature (chemical) disinfection. These methods include manual disinfection by means of soaking, spraying, or wiping with a chemical disinfectant, automated chemical disinfection within a washer-disinfector, or automated thermal disinfection that takes place under controlled temperature conditions in a pasteurizer or washer-disinfector or by immersing the devices into hot water at a specified temperature for a specific amount of time.
In the United States high-level disinfection is the minimum treatment recommended by CDC in guidelines for the processing of semicritical devices.28
The most widely used high-level disinfection process is the use of hot water typically at >70°C. Common chemical high-level disinfectants include a number of glutaraldehyde-, chlorine dioxide-, hydrogen peroxide-, and peracetic acid-based formulations; these are commercially available disinfectants but often require regulatory approval in different countries such as being cleared by FDA in the category of sterilants/disinfectants.
Intermediate-level disinfectants are not necessarily capable of killing bacterial spores, but they do inactivate Mycobacterium
species, which are significantly more resistant to chemical disinfectants than other vegetative bacteria. These disinfectants are also expected to be effective against fungi including asexual spore forms but not necessarily dried chlamydospores or sexual spores as well as lipid and many nonlipid medium-sized and small viruses. The specific activity of these disinfectants can vary and may require specific antimicrobial test requirements to support label claims in different areas of the world (see chapter 61
). Examples of intermediate-level disinfectants can include alcohol-based formulations (eg, containing 70%-90% ethanol or isopropanol), chlorine compounds (free chlorine, ie, hypochlorous acids derived from sodium or calcium hypochlorite, or chlorine dioxide, 500 mg/L, and certain chloramines), and some phenolic or iodophor preparations, depending on the formulation and label claims. The effects of intermediate-level disinfectants can often vary in efficacy against specific microorganisms, for example, alcohol efficacy against nonenveloped viruses (see chapter 19
Low-level disinfectants cannot be relied on to destroy, within a practical period, bacterial spores, mycobacteria, most fungi, or all small or nonlipid viruses. But these disinfectants may rapidly kill vegetative forms of other
types of bacteria and most fungi as well as medium-sized or lipid-containing viruses. Examples of low-level disinfectants are products based on quaternary ammonium compounds, iodophors, or phenolics. They, like other disinfectants, can be marketed in a variety of ways such as concentrates (requiring dilution in water before use), ready-to-use products (not requiring dilution), two-part components (that are activated prior to use), and as saturated wipes. Many of these products, such as those based on quaternary ammonium compounds, may be used for both cleaning and disinfection due to the surfactant activity in aiding the physical removal of microorganisms from surfaces. The antimicrobial activity of these products can be variable, depending on the concentration and/or formulation of the active ingredients. Some iodophor- and phenolic-based disinfectant formulations may be labeled for use for intermediate-level or low-level disinfection depending on the concentrations of the products being used. All disinfection chemicals do not have this capacity, such as the limited capacity of many quaternary ammonium compound-based formulation to meet the tuberculocidal or viricidal criteria of intermediate-level disinfectants.30
Overall, care should be taken to review and understand the label claims associated with chemical disinfectants to ensure safe and effective use, rather than depending on a list of antimicrobials present.
Chemical disinfection occurs with many types of chemicals and chemical processes. The correct disinfectant to be used depends on the device material, device characteristics, and level of disinfection necessary. It is also important to ensure that the chemicals are labeled for use on medical devices, when applicable, and approved for use in accordance with local regulatory requirements (eg, in the United States, cleared by FDA or US Environmental Protection Agency [EPA] depending on their use and label requirements), and used in accordance with the label claims. In many applications, removal of disinfectant residuals may be required due to toxicity concerns postdisinfection and depending on the subsequent use of the device or equipment. It is also important in these cases that the disinfected surfaces are not recontaminated, such as in the case of using contaminated rinse water.31
The following section provides a brief overview of some of the most widely used disinfectants for device disinfection.
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