Manual Cleaning of Surgical Instruments

Instruments may be rinsed and cleaned manually with hand brushes (with or without detergents) before sterilization. Manual cleaning is preferable for delicate or detailed instruments and for instruments that are heat or moisture sensitive.³¹ Manual cleaning may be inferior to some mechanical cleaning devices for general instruments.³¹ Use of enzymatic cleaners or detergents that are compatible with the material and design of the instruments may help to loosen blood, tissue, and gross debris. Use of cleaners that produce bubbles may make instruments harder to rinse and should be avoided.⁵ Surgical instruments must be completely submerged and rinsed to minimize aerosolization of contaminants.⁴ Manual cleaning may require the use of soaps and detergents, and this requires exposure of instruments and staff to these chemicals. Brushes should be used on any instrument with a lumen. Abrasive brushes and sponges are often used but may damage delicate surgical instruments. Manufacturers’ instructions should be followed in cleaning these specialized instruments. Manual cleaning can be time-consuming and costly. Special training for staff on proper cleaning techniques and handling of delicate instruments and protection from chemicals and injuries are required.

Mechanical Cleaning of Surgical Instruments

Mechanical cleaning of surgical instruments includes the use of ultrasonic cleaning devices, washer decontaminators/disinfectors, or washer sterilizers.⁴ Mechanical cleaning is the preferred method of cleaning as it facilitates washing and rinsing without the risks of manual cleaning and efficiently removes soil and debris.¹¹ Many different medical mechanical washing decontaminators/disinfectors are available. The manufacturer’s instructions on the recommended mechanical cleaning method and detergents must be followed to prevent damage to the surgical equipment.¹¹ Ultrasonic cleaning devices utilize the process of cavitation, whereby ultrasonic waves are used to create minute gas bubbles, which then implode, creating a minute vacuum that facilitates the removal of particles and debris.^1,4,11 Washer decontaminators/disinfectors are akin to dishwashers in that they use a combination of circulating water and detergents to facilitate the cleaning process. Washer decontaminators carry no specific claims of antimicrobial efficacy, whereas washer disinfectors can achieve high-level disinfection.⁵ Washer sterilizers are modified steam autoclaves that bubble steam through water and detergent to accomplish the cleaning. These various mechanical devices are quick and are capable of removing tightly bound particles that are poorly removed by manual cleaning, but mechanical devices are obviously more expensive. These different cleaning devices use variations in pH of detergent solutions and possible addition of enzymes to facilitate the process. Care should be taken to follow the directions of the manufacturer in selecting cleaning solutions. Once the cleaning cycle is complete, dense particles fall to the bottom and finer soil rises to the surface; therefore instruments must be thoroughly rinsed.⁴ The residual cleaning solution itself may be a source of contamination, as it is not always designed to deliver specific levels of disinfectant efficacy (especially in ultrasonic cleaners).³¹

In summary, manual cleaning is preferable for certain delicate instruments but is less efficacious than the various mechanical cleaners. Mechanical cleaners are expensive but effective and therefore are preferred for most instruments. If detergents, enzymatic cleaners, or disinfectants have been used in the cleaning process, instruments should be thoroughly rinsed before sterilization, as chemical residues could affect the sterilization process or result in harm to the patient or to hospital personnel.⁵

Wrapping Materials

Once the surgical equipment has been properly cleaned, the instruments must be organized and prepared for wrapping. Instruments should be dry before sterilization; however, few veterinary practices have filtered medical-grade compressed air available, which is the only approved method for drying instruments.⁵ Clinicians must weigh the risks of lint contamination or airborne contamination when resorting to alternate means. Packaging and wrapping of cleaned and disinfected instruments in preparation for sterilization should be performed in a controlled environment to prevent contamination during processing. The instrument packing area should be a clean area with limited access, where airflow, temperature, and humidity are controlled and clean surgical scrubs and caps must be worn. Specific guidelines and recommendations on packaging system parameters for the various sterilization techniques and controlled environments during sterilization are published.¹¹ Wrapping materials should be permeable to steam or appropriate gases, resistant to heat, and resistant to physical damage; they should possess minimal wrap memory and should have a long shelf-life with sufficient strength and durability. The wrapping material must be free of toxic ingredients and dyes that might fade or run and must provide a barrier to microorganisms and fluids.¹¹ Double-layer wrapping has been traditionally preferred over single-layer wrapping for longer storage times and reduced contamination, but this may be dependent on the material.^12,39 A chemical or biologic indicator specific to the sterilization process should be placed in the pack before wrapping. The packaged instruments should be wrapped in a manner that facilitates unwrapping without breaking sterile technique.

The most common wrapping materials used for steam sterilization include cotton muslin (140 or 270 count), pima cotton, nonwoven paper material (more flexible and durable), paper-plastic pouches, nonwoven polypropylene fabric, and plastic pouches. The packages may be taped with specifically designed autoclave tape or sealed with heat-sealing devices, or they may be self-sealing. The ideal packaging material is resistant to penetration, allows ready passage of the sterilizing agent, allows for aeration (in the case of ethylene oxide), prevents microbial penetration, and resists moisture penetration. It should be easy to work with and should be transparent and economical. The ideal combination does not exist. Cotton muslin can generate lint, is not moisture resistant, and requires a double-layer wrap, but it can be used with both gas (ethylene oxide) and steam sterilization. Reusable woven textiles are the most permeable type of wrap and therefore have the shortest shelf-life.² Paper should not be reused because of the risk of unnoticed perforations; it requires a double layer and is not moisture resistant. Linens and paper wrapping cannot be used with hydrogen peroxide gas sterilization. Nonwoven polypropylene fabric and plastic pouches are moisture resistant; however, a double layer is still recommended to prevent puncture or contamination of the material. The most commonly used wrapping materials for ethylene oxide sterilization are polyethylene/mylar, polycoated paper, and uncoated paper.⁷ Nylon, polyvinylchloride, polyvinylidene chloride (kitchen wrap), and foil should not be used.

Regardless of the type of wrap or sterilizer, certain principles apply to making up the packs to be sterilized. Instruments with hinges should be opened to maximize the surface area accessible to the sterilizing agent. Packs should not be too densely packed for the same reason. Furthermore, care should be taken as to the size and weight of the pack to ensure that it is manageable by all personnel. Once wrapped, surgical instruments should be placed in a perforated tray, box, or basket in a manner that protects the instruments from damage and prevents puncture to the wrapping material.¹¹ Wraps with perforated trays should be placed flat, and those with solid trays or plastic pouches should be placed on edge.⁵ Wrapped linens should be folded in such a way as to facilitate easy opening without breaking sterile technique.

Liquid Chemical Germicides (Cold Sterilization)

The term cold sterilization is used to refer to the process of soaking instruments or other equipment in a disinfectant (frequently a liquid) to achieve acceptable reductions in microbial presence. The use of chemicals to sterilize equipment or surfaces has been practiced for centuries.¹⁴ Despite this experience, agents that combine acceptable efficacy (especially against spores) with low levels of user, instrument, and environmental toxicity have proved elusive. Additionally, these products suffer from decreased ability to access microbes in the interiors or crevices of items when compared with thermal methods of sterility.³¹ Furthermore, their use is limited in that they typically need to be rinsed with water that in turn needs to have sterility guaranteed. Most chemical liquid sterilants do not have an appropriate biologic sterility indicator available.³¹ Currently, cold sterilization is not advised for surgical equipment or other items that, if contaminated, would carry the risk of highly significant sequelae. These agents are commonly investigated for use with endoscopic equipment, but their approval by different manufacturers of endoscopic instruments varies, and such recommendations should be heeded.

Glutaraldehyde, one of the most frequently used chemical sterilants, has reasonable efficacy against bacterial spores, but only with prolonged exposure.³⁵ Glutaraldehyde is acidic in aqueous solution and must be alkalinated to boost its efficacy. It has a shelf-life of approximately 14 days, although newer formulations (glutaraldehyde-phenol-sodium, potentiated acid glutaraldehyde, and stabilized alkaline glutaraldehyde) have an extend shelf-life of around 28 days.³¹ Additionally, it is irritating to the respiratory passages and can even decrease pulmonary function.³ The use of ortho-phthalaldehyde (OPA, commercially available as Cidex) may be superior in clinical settings as it is less irritating and more efficacious without requiring pH adjustment.^31,33 Ortho-phthalaldehyde causes staining of skin and tissues and has multiple efficacy claims worldwide as a result of different testing methods employed by certifying bodies.³¹ Glutaraldehyde is considered a high-level disinfectant but is too expensive to be used on noncritical items. A similar product, formaldehyde, is available as a 37% aqueous solution (formalin). It is slightly less efficacious than glutaraldehyde and is considered a carcinogen, which makes it a poor candidate for most clinical applications.³¹

Hydrogen peroxide has shown some promise as a chemical sterilant by producing hydroxyl free radicals to interfere with membranes and nucleic acids. Commercially available concentrations are not sufficient to achieve adequate antimicrobial activity. Concentrations of 7.5% or greater exceed the efficacy of glutaraldehyde.³¹ Hydrogen peroxide must be carefully stored in dark containers to prevent loss of efficacy. Additionally, it is toxic to mucous membranes and can discolor some metals.³¹

The oxidizing agent peracetic acid has good antimicrobial efficacy and breaks down into environmentally inert products, but it is relatively unstable, leading to a short useful efficacy (approximately 6 days).³¹ Some peracetic acid systems are marketed that yield primarily nontoxic acetic acid. Some automated devices have been marketed using peracetic acid or peracetic acid in combination with hydrogen peroxide. The expense of these units has precluded their widespread adoption despite good efficacy.

Other compounds such as quaternary ammoniums and hypochlorites should be considered as disinfectants rather than sterilants. At certain concentrations or exposure times, they may reach antimicrobial levels associated with sterility, but their overall efficacy or undesirable properties make them poor candidates for use as sterilizing agents. The use and development of additional agents such as superoxidized water (currently available in some countries as Sterilox [Sterilox Technologies, Inc., Philadelphia, PA]) and various proprietary chemicals can be anticipated.