Cleaning (or Precleaning): The removal, usually with detergent and water, of adherent visible soil (blood, protein substances and other debris) from the surfaces, crevices, serration, 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. [AAMI, 1995]
The first step in preparing an instrument for reuse after it has been used on a patient is cleaning. The importance of this step cannot be underestimated, as studies [Alfa, 1998] have shown that a soiled instrument cannot be effectively sterilized. This is because the soil shields bacteria and viruses from the sterilizing medium. As a result, the bacteria and viruses may very well survive the sterilization process and can cross infect the next patient.
Methods
Before any specific methods of cleaning instruments can be discussed, the issue of how to protect the staff from the possibility of infection must be considered.
General Precautions
Healthcare workers who do the hands-on work of cleaning soiled instruments should be protected from the possibility of infection from infectious material on the instruments. This is not just a good idea; it is the law. OSHA, the Occupational Safety and Health Administration of the U.S. Department of Labor has issued regulations (29 CFR 1910.1030 subpart Z) concerning handling of bloodborne pathogens that spell out universal precautions that must be taken to avoid, or at least minimize the chance that a healthcare worker will be exposed to infectious material. Some of the most important points discussed in these regulations are:
• provide initial and annual training on the bloodborne pathogen regulations,
• provide personal protective equipment such as disposable gloves,
• dispose of soiled dressings and potentially contaminated waste according to biohazardous material regulations,
• but, the use of personal protective equipment is required only when there is reasonably anticipated exposure to blood or other potentially infectious materials.
Since soiled instruments will normally have body fluids on them, personnel assigned to handle and reprocess them must use universal precautions.
Manual Cleaning
The oldest method of cleaning dental and medical instruments is manual cleaning. This method is still used frequently in areas ranging from the small medical or dental office to the largest hospitals. Manual cleaning has the advantage of flexibility, in that any type of instrument can be cleaned. It also has the weakness that the cleanliness of the instruments will be different from worker to worker, since each person will vary in technique to some degree. It also has the drawback that the healthcare workers are more exposed to body fluids than in machine cleaning, as they would spend more time in contact with the soiled instruments.
Recommended procedures for manual cleaning are to first soak the instrument in a tepid or lukewarm water or detergent bath for at least 10 minutes, preferably until all soil on the instrument is softened. This step softens and loosens much of the soil that may have dried on the instrument between the time it was used and the time cleaning is begun. The duration of the soak depends upon how much soil is on the instruments and how long the soil has been allowed to dry. The use of enzyme detergents is preferred, as they help to break up organic soil more readily and rapidly than do conventional detergents.
The next step is to completely brush the instrument with a medium-soft brush while it is in the soak bath. In the case of tubed devices like endoscopes and handpieces, the insides (tubes, lumens, channels, etc.) should be brushed out as well. Care should be taken to use brushes recommended by the manufacturer so as to avoid damaging the instrument. Brushing must be done under the surface of the soak bath with brush strokes away from the body to avoid exposure to spray from the brush, removing the instrument from the soak bath only to inspect its cleanliness. This will remove most to all of the soil on the instrument. The instrument must then be rinsed with clean water, and if difficult-to-remove soil remains, another enzyme soak followed by brushing and rinsing must be done. Clean detergent solutions must be used for each cleaning session, so as to make sure that soil that was removed from on instrument or set does not deposit on the next instrument, creating the chance for cross infection.
Manual cleaning is the first step. It removes a great deal of soil from instruments, but does not do a very good job on removal of very small particles that may be found in hinges, textured surfaces, and other hard-to-reach parts of the instruments. For this, ultrasonic cleaning provides a solution that is the next, essential step in reprocessing instruments safely.
Ultrasonic Cleaning
Ultrasonic cleaning is the follow-up to manual cleaning. While manual cleaning removes most or all of the visible soil from an instrument, it cannot remove small or microscopic particles that are protected by the texture of a surface or design features like hinges. Ultrasonic cleaning works by creating microscopic bubbles in the solution that collapse when they contact the instrument. When the bubbles collapse, the energy that was used to make them is released. This energy 'kicks' any soil that is in the area off the instrument. This process is called cavitation. To avoid the soil particles attaching to the instrument again, detergents are mixed into the ultrasonic bath. These detergents help suspend the soil that is removed from the instruments in the bath. Ultrasonic processing cleaning should be done for a duration specified by the detergent or ultrasonic bath manufacturer, whichever is longer. The detergent solutions must be changed following the instructions of the manufacturer of the detergent or the ultrasonic bath, whichever states a shorter change interval. This procedure ensures that the potential for cross contamination of instruments and instrument sets is reduced to a minimum. Following ultrasonic cleaning, the instruments are rinsed with clean water and dried. Distilled water is preferred, to ensure removal of as much detergent as possible, but is only essential if the tap water has a high mineral content that could spot or . After they are dry, they may be packaged for terminal sterilization, the step that completes the reprocessing procedure.
Automatic Cleaning
Some offices, and many clinics and hospitals do not exclusively use manual cleaning of instruments that are being reprocessed. Larger practices need to reprocess more instruments than can reasonably be done by hand, and so use automatic cleaning machines. These machines may resemble home dishwashers or be specialized for the specific needs of cleaning endoscopes or dental handpieces. In all cases, they are more rugged and powerful and have been validated to meet the special needs of cleaning dental and medical equipment. All washers sold in the US medical and dental market have been validated by the manufacturer and the FDA has reviewed the validation data prior to the manufacturer being given permission to market the washer by that agency. A more-rigorous evaluation is done for disinfection and sterilization claims. These units also provide options for dealing even more specialized situations. These options may include specialized racks that allow cleaning of the interior of anesthesia tubing, for example, and a wide range of temperature settings that allow the goods to be processed at the maximum safe temperature for their use. Higher temperatures both speed cleaning, which is important in a high-volume setting, and provide some disinfection of the goods, which is part of the point of reprocessing instruments in the first place.
Aside from increasing throughput and providing specialized solutions to difficult cleaning situations, automatic washers serve one very important purpose, no matter what their specialized capabilities. This purpose is to provide the same level of cleaning every time. These machines remove the variability of cleaning discussed previously. When used as recommended by the manufacturer, and they are properly maintained, these machines eliminate one source of uncertain results in instrument reprocessing, the human factor. In addition, they decrease opportunities for personnel to be exposed to infectious soil by doing some of the work that would otherwise require hands-on involvement of a healthcare worker, providing another benefit from their use.
Automatic washers have more things in common than differences. There are basically three classes of washer found in the healthcare reprocessing setting. These are washers, washer-disinfectors and washer-sterilizers. In the US, these categories are defined and regulated by the Food and Drug Administration (FDA), and a unit may not be offered for sale without the permission of that agency. Only washers and washer-disinfectors intended to process "general purpose" articles, such as laboratory glassware, pipettes, bottles and containers, are exempt from FDA review, unless they are promoted for use in the reprocessing of reusable medical devices [FDA, 1998].
The differences between these categories are given in the table below.
| Category | Performance |
| Washer | removes soil from goods |
| Washer-disinfector | removes soil from goods, provides at least a 1,000-fold reduction in the number of viable organisms present on the instrument by use of a hot-water (180-200°F) or chemical disinfectant cycle. |
| Washer-sterilizer | removes soil from goods, provides a sterility assurance level of one chance in one million that the items processed will have a viable organism on them after processing. |
Each of these classes have advantages and disadvantages, which are discussed below.
Washers
Washers provide the basic function of cleaning that is needed to successfully reprocess instruments. The capabilities of a specific model and variability of cleaning results from one washer to then next must be taken into account to make an informed purchase decision. FDA permission to market provides a baseline, but the best information, including information on reliability, cost of ownership and ease of use, can be found by surveying the literature for so-called 'round-robin' studies in which products are compared.
Washer-Disinfectors
Washer-disinfectors performance meets certain criteria, which were described in the table above. Per FDA, there are three levels of disinfection that may be claimed. The least demanding is low-level disinfection, in which 6-log (one-million fold) reduction of a suspension of vegetative organisms such as Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli or representatives of the Klebsiella-Enterobacter group is accomplished. The next level of disinfection is intermediate-level disinfection in which 3-log (one-thousand fold) reduction of an appropriate mycobacterium species is accomplished. The most demanding is high-level disinfection, in which 6-log (one-million fold) reduction of an appropriate mycobacterium species is accomplished [FDA, 1998a]. In order to meet these criteria, washer-disinfectors must thoroughly clean the instruments as well as subsequently disinfect them. This is because one cannot disinfect or sterilize soil. Again, some washer-disinfectors are better suited for some cleaning tasks than others, so review of the manufacturer's literature and published articles is an essential part of a purchase decision.
Washer-Sterilizers
These units are used to clean and sterilize items that do not require packaging before use. The items processed in these unit are those that do not generally come in direct contact with open wounds. These devices do not allow items to be wrapped in a sterile barrier, so the items are unsterile by definition as soon as the washer-sterilizer door is opened. Thus, washer-sterilizers are used for things like pans and trays that receive instruments in an operatory. For those situations in which a sufficient number of these items are to be reprocessed, washer-sterilizers are a good investment. Note also that washer-sterilizers are steam sterilizers and cannot be used for reprocessing materials or devices that cannot tolerate the heat and pressure of a steam sterilization cycle.
Instrument Preparation for Cleaning in an Automatic Washer
Regardless of the washer type used, instruments must be prepared for processing before being placed into a washer, with the extent of preparation depending upon the capabilities of the washer. The actual preparation must be done in accord with the washer manufacturer's instructions. For the simplest washers, manual presoaking and sonication remain as necessary reprocessing steps. More-sophisticated washers include a presoaking step in the automated process. In all cases, standard operating procedures must be developed that take the capabilities of the washer into account, as assumption of a capability that is not present can compromise worker and patient safety.
Use of Containers
In many practices, instrument cassettes are used to hold instruments both during washing and sterilization. These cassettes use rubber strips to hold the instruments in place and have many perforations that allow free flow of wash water/detergent solution through the cassette and over the instruments. Their use is only recommended in conjunction with automatic washers, as manual methods will not provide sufficient penetration of the cassette and the instruments within. Following the cleaning procedure, the cassette is dried and wrapped for sterilization.
Care of the Washing Equipment
Automated washers and washer-disinfectors provide a consistent level of cleaning if maintained properly. However, the internal parts of the unit, which are normally in a warm, moist atmosphere, can provide sites for the growth of pathogenic organisms in the form of biofilm [Health InfoCom Network News, 1991]. These organisms can be transferred to and infect patients if the instrument is not sterilized after cleaning. The best approach is to use a program of preventative maintenance that includes disinfection of the areas of the unit that are exposed to moisture and not actively rinsed. The manufacture of the unit should be consulted to determine where these areas are located. If the unit was cleared by FDA since about 1992, the manufacturer will have had to document these potential problem areas to receive their permission to market the device.
Multi-Step Automatic Cleaning
The ultimate in automatic cleaning is the multi-step or 'tunnel' washer. These units incorporate separate soaking, sonication, washing, rinsing and drying stations and automatically transfer racks of instruments between these stations. These are expensive machines whose cost can be justified only by the highest-volume instrument processing requirements. However, these machines also provide the most-complete automation of instrument processing possible, permitting soiled instruments to be placed in a rack at one end of the unit and to be removed clean and dry and ready to be wrapped for terminal sterilization at the other end of the unit.
Difficult to Clean Instruments
Dental and Orthopedic Handpieces
Cleaning of handpieces is more difficult and requires more attention than cleaning of less-complex instruments. Handpieces are precision, turbine-driven instruments that have both air and water flowing through them. In normal use, these devices are in direct contact with internal body tissues. Because of their design and use, there is a good chance that body fluids and tissues may contaminate the inner surfaces and mechanism of the handpiece. If this soil is not removed, it may be sprayed out of the handpiece and into the next patient. To avoid this, the manufacturers' instructions for cleaning procedures must be followed closely [CDC, 1993]. In addition, the usable life of these expensive instruments is shortened by allowing soil to accumulate in their mechanisms, providing an economic reason as well as a patient care reason to clean the units properly.
All water and air channels in a handpiece are small, making it difficult to gain access to them and making cleaning difficult. Also, when the handpiece is turned off, the water supply tends to suck water back, pulling soil into the handpiece, and into the areas most difficult to access. How, then does one clean these instruments? The same sort of sequence described above for regular instruments is used. This is to remove gross soil, fine soil and microscopic soil, in that order.
Gross Soil Removal
There are two very different parts to removal of soil from a handpiece. These are the cleaning of the outside and the cleaning of the insides. Cleaning of the outside is no different than cleaning of a less-complex instrument, and is described in the sections above. Cleaning of the inside is very different.
The first step in cleaning the inside of the handpiece is to attempt to remove the soil that was sucked into the water channels. To do this, you simply operate the handpiece in the normal manner for 20-30 seconds, pointing the instrument into a narrow-necked receptacle or drain, or a high-speed evacuation receptacle. The handpiece head must be inside the neck of the receptacle, ensuring that none of the spray or spatter is allowed to escape and contact the healthcare worker doing the cleaning. This action flushes out most or all of the soil in these channels. Some handpiece manufacturers also suggest the use of lubricating oil fed through an automatic handpiece lubricator for this rinsing.
Following this, the handpiece should be disassembled in accord with the manufacturer's instructions and cleaned following the manual and ultrasonic procedures described above. Note that the handpiece manufacturer's instructions are the final authority on the specific procedures used on a particular handpiece.
Endoscopes
Endoscopes may be even more difficult to clean than handpieces. They are currently the most challenging reusable medical device for cleaning and sterilization. This is because of their longer length and the relative narrowness of the tubing in them. Rigid endoscopes, like those used in arthroscopies and laporoscopic cholycystectomies, are typically able to be disassembled from cleaning, which makes their cleaning relatively easier. Flexible endoscopes, like those used in colonic procedures, are more complicated and generally cannot be disassembled. This causes them to present the greatest challenge to cleaning.
Manual Cleaning-Rigid Endoscopes
Cleaning of endoscopes is done in a manner similar to normal instruments, with the exception that both the inside and outside of the endoscope must be cleaned. The first step is a presoak in enzyme detergent solution, followed by disassembly of the endoscope. All parts of the endoscope are then cleaned by brushing beneath the surface of the detergent solution to remove visible soil from the instrument. At this point, all surfaces of the endoscope are rinsed and inspected for soil. If any is found, the previous steps should be repeated. The inside of the outer tube that makes up the endoscope requires special attention, as it is frequently coated with a low-friction material like Teflon®. If scratched during cleaning, the operation of the endoscope may be adversely effected. However, the tube must also be clean, which is not easy to accomplish without brushing, so only brushes recommended by the manufacturer should be used in these areas. After all visible soil is removed, the endoscope components should be rinsed with clean water or a final rinse with 70% ethanol or isopropanol may be used to both provide final disinfection and drying of interior channels of an endoscope [BSG, 1997].
The next step is ultrasonic cleaning. This is done in a manner similar to what is done for normal instruments, and does not require any further discussion. After cleaning, the endoscope components are to be rinsed with water or alcohol and allowed to dry. Any joints requiring lubrication are then lubricated and the endoscope may be reassembled in preparation for sterilization. If the endoscope is to be disinfected using a liquid disinfectant, reassembly and lubrication should be done after disinfection.
Manual Cleaning-Flexible Endoscopes
The inital steps of cleaning of flexible endoscopes are similar to what has been described above, except that all valves on the endoscope must be locked open to ensure flow of cleaning and disinfecting solutions though them. All removable components must be removed and cleaned separately. The external surface is brushed clean in a manner similar to the rigid endoscopes described above. A syringe is used to direct cleaning solutions through the endoscope toward the end of the endoscope that is normally in contact with the patient. That end of the endoscope must remain submerged in the detergent solution to avoid splashing workers with soil. While the endoscope is being flushed, any directional controls should be manipulated through their full range of motion to ensure that as much of the endoscope as possible is contacted and rinsed by the detegent and rinse water. Since it is impossible to inspect the inner channels of the endoscope for cleanliness without special instrumentation, this is a case where the adage, "If you can't be good, be thorough," applies. As is the case for rigid endoscopes, a final rinse of clean water or alcohol should be used. The alcohol provides low-level disinfection, an important consideration for devices that even when cleaned correctly can harbor living microorganisms [Forbes, 1999].
Ultrasonic cleaning should follow manual cleaning for all submersible parts of the endoscope. Note that due to the small diameter of the endoscope lumens, ultrasonic waves will not penetrate much more than one inch from the end of the tube, so this cleaning method's effects are limited to the outside of the endoscope.
Automatic Cleaning
Automated systems exist for cleaning endoscopes. These include special racks for normal washers and dedicated endoscope washers. As is the case for other automatic washers, performance will vary between different washers from different manufacturers, with FDA approval effectively providing a minimum performance standard. Note that FDA does not test the items submitted to it, but evaluates the data submitted to it by the manufacturer. Preparation for washing depends for upon the capabilities of the washer, but precleaning and disassembly are always an appropriate first step, since it is difficult for any washer to remove hard, dried soil. Some automated endoscope washers also employ ultrasound to aid in cleaning, but as discussed before, ultrasound does not effectively penetrate a lumen for any significant distance, and this approach therefore primarily benefits cleaning of the outside of the endoscope. Prior to making a purchase decision, the literature must be reviewed for performance and reliability information.
Summary
Cleaning is the first and possibly the most important step in reprocessing of reusable medical and dental instruments. The sequence soak, wash, rinse, dry (with appropriate preparation of the instrument) will provide a clean instrument that can be readily disinfected or sterilized prior to its next use on a patient. Automated systems improve both the number of instruments processed in a given time period and the consistency of cleaning of these instruments. Difficult-to-clean instruments, like handpieces and endoscopes require special attention and care on the healthcare worker's part to ensure their fitness for reuse.
References
AAMI, 1995: Association for Advancement of Medical Instrumentation (AAMI) Standards and Recommended Practices: Volumes 1 and 2: Sterilization, 1995 Edition.
Alfa, 1998: "Comparison of liquid chemical sterilization with peracetic acid and ethylene oxide sterilization for long narrow lumens," Michelle J. Alfa, Pat DeGagne, Nancy Olson, Romeo Hizon, American Journal of Infection Control 1998; 26: 469-77.
BSG, 1997: "Cleaning and Disinfection of Equipment for Cleaning and Disinfection of Equipment for Gastrointestinal Endoscopy," British Society of Gastroenterology, Guidelines in Gastroenterology, 1997.
CDC, 1993: "Recommended infection-control practices for dentistry," Centers for Disease Control and Prevention, MWMR 1993;42(No. RR-8), 1993.
FDA, 1998: "Guidance Document For Washers And Washer-Disinfectors Intended For Processing Reusable Medical Devices," June 2, 1998, U.S. Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health, Infection Control Devices Branch, Division of Dental, Infection Control, and General Hospital Devices, Office of Device Evaluation, http://www.fda.gov/cdrh/ode/washdsnf.html.
FDA, 1998a: "Guidance on the Content and Format of Premarket Notification 510(k) Submissions of Washers and Washer-Disinfectors-Draft Guidance," U.S. Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health, Infection Control Devices Branch, Division of Dental, Infection Control, and General Hospital Devices, Office of Device Evaluation
Forbes, 1999: "Blood Money," Neil Weinberg, Forbes, p. 123, March 22, 1999.
Health InfoCom Network News, 1991: Nosocomial Infection and Pseudoinfection from Contaminated Endoscopes and Bronchoscopes -- Wisconsin and Missouri, Health InfoCom Network News, Volume 4, Number 25, Page 6, December 25, 1991, Scottsdale, AZ.
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