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May 31, 2024
Ultrasonic cleaners in hospitals provide an automated cleaning process for surgical instruments and support compliance with the manufacturer's instructions for use (IFUs) of those instruments. Many complex instruments have crevices or narrow lumens, which can be difficult for other washing methods, such as a washer/disinfector, to clean. Correctly performing ultrasonic cleaning requires knowledge of the equipment, cleaning chemistries, and techniques to maximize cavitation and remove soils.
Ultrasonics can be particularly useful for washing hard-to-reach areas on a medical device, including fine serrations and box lock joints. Ultrasonic cleaning is also useful on small surgical instruments, including select microsurgical and ophthalmology devices.
Ultrasonic cleaning is only one part of the complete cleaning (or decontamination) process. The cleaning process starts in the procedure room, where pre-treatment products are applied to keep surgical instruments moist. Once the instruments arrive in the sterile processing department (SPD) for decontamination, they are rinsed, and lumens are flushed. They are often soaked for an amount of time specified in the IFU. Manual cleaning uses specialized instrument cleaning brushes and cleaning chemistries to remove soils from instrument surfaces. If the device IFUs require ultrasonic cleaning, this is the next step in the decontamination process.
Ultrasonic cleaning provides the power needed to remove residual soils from intricate instruments. In sterile processing, these ultrasonic cleaners use powerful sound waves to create cavitation capable of removing residual soils from complex instruments.
Ultrasonic cleaners work based on a successful combination of three key parameters:
First, instruments are fully submerged in a cleaning solution with detergents such as Prolystica™ HP Instrument Cleaning Chemistries in a specialized basket or holder. The ultrasonic cleaner then creates high-frequency sound waves that agitate the solution.
Ultrasonic systems consist of generators and transducers. The generators produce high-frequency electrical signals, which transducers convert into vibrations to agitate the solution. Some systems mount the transducers to the bottom of the tank. Since the ultrasonic waves are coming up from the bottom of the tank, cavitation may only reach instruments in the bottom tray.
Large-capacity ultrasonic cleaners, such as the InnoWave™ Pro Sonic Irrigator, mount transducers to the sides of the tank to evenly clean multiple layers of trays.
As the ultrasonic waves pass through the solution, they create alternating high and low-pressure cycles. During the low-pressure cycle, small bubbles are formed. When the high-pressure cycle occurs, these bubbles rapidly collapse or implode in what is known as cavitation.
The bubbles imploding across the instrument's surfaces act like scrubbers and remove contaminants from the devices' surfaces.
The solution the instruments are submerged in allows for efficient cleaning, while the use of pressurized flow can provide additional mechanical cleaning to the internal channels of lumened or cannulated medical devices.
Innowave Ultrasonic Irrigators have sonic irrigation capabilities, delivering ultrasonic energy and cavitation to reach the devices' exterior and interior. Lumen flushing facilitates the cleaning of the challenging soils within lumens, and power flushing provides a high-pressure irrigation force through lumens. This combination provides cleaning inside these hard-to-reach lumens.
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Typical steps for using an ultrasonic cleaner for surgical instruments include:
After the ultrasonic process, instruments must be thoroughly rinsed with critical water. Though the instruments have been cleaned and rinsed, they may still be contaminated with microorganisms. Appropriate precautions must be taken to ensure technicians are not exposed to potential pathogens left on devices. Processing in an automated washer after an ultrasonic can offer thermal disinfection to make the devices safe to handle. Always refer to the device IFU before running a device through a washer/disinfector.
Incorrect cleaning and sterilization of ophthalmic instrumentation have been linked to the formation of Toxic Anterior Segment Syndrome (TASS). TASS is an acute inflammation of the anterior chamber of the eye occurring postoperatively and has caused blindness in some patients. It occurs when foreign matter such as enzymatic cleaners, residual debris, steam chemical carryover, powder from surgical gloves, or other material is transferred to the eye during surgery.
Due to the low threshold of contaminant needed to cause TASS, ophthalmic instrumentation must undergo special processing. For example, some manufacturers require the use of treated water only instead of cleaning chemistries.
Many organizations, such as the Association for the Advancement of Medical Instrumentation (AAMI) and the Association of periOperative Registered Nurses (AORN), provide special recommendations for ophthalmic instrumentation. A common recommendation is that surgical eye instruments be cleaned in a designated area and with an ultrasonic unit dedicated to these instrument sets. A dedicated sonic is often recommended because enzymatic detergents cannot be used on these instruments, and a shared ultrasonic needs to be cleaned before use.
Beyond cleaning - selecting a suitable detergent for ultrasonic cleaning is an important consideration. The cleaning chemistry's formulation should be:
Prolystica Instrument Cleaning Chemistries go beyond cleaning to meet all these requirements.
Suitable cleaning chemistries designed for use on medical instruments (with or without enzymes) and optimized for use at lower temperatures should be used. Most ultrasonic units heat the solution to temperatures ranging between 27 °C (80 °F) and 49 °C (120 °F). Enzymatic-based chemistries are sensitive to the effects of temperature ranges. The enzymes work less efficiently or not at all at suboptimal temperatures. Ensure the enzymatic cleaning chemistry is compatible with the ultrasonic cleaner's temperature range.
The medical instrument manufacturer's written instructions should provide specific details on solutions and process conditions for cleaning various instruments. In addition, maintaining a proper level of solution in the tank is important. Low levels of solution can cause adverse effects on the cleaning process as well as the unit itself.
As noted above, cavitation is the cleaning power of ultrasonic cleaners. Conditions or materials that prevent the formation of cavitation prevent cleaning. Since sound waves pass through materials differently, the acoustical properties of the materials have a significant impact on the formation of cavitation. Materials that block or absorb sound waves and inhibit the formation of cavitation include plastics, such as polycarbonate and silicone. On the other hand, metals readily conduct sound waves, which is why metal baskets are often used to hold instrumentation.
Some materials are also not appropriate for ultrasonic cleaning, as they can be damaged:
Overloading the ultrasonic can also impede sound wave transmission, reducing cavitation and cleaning effectiveness. Weight limitations, as defined in the IFUs, must be followed. In addition to too much weight, too much gross soil within the tank can also impede the transmission of sound waves. Tissue, bone cement, and other residuals can block or absorb sound waves and reduce cavitation. Lastly, improper cleaning agents may inhibit the formation of cavitation. Avoid cleaning chemistries with excessive foaming, and only use cleaning agents specifically designed for ultrasonic cleaners.
An ultrasonic cleaner must be maintained in proper working order according to the manufacturer's IFU. Staff must perform daily maintenance, including solution changes and degassing. Larger or more complex ultrasonic cleaners may require calibration and preventative maintenance. Quality controls ensure that the process is followed, the equipment functions, and the expected outcome is achieved.
Ultrasonic Indicator – a test that provides a realistic challenge using a synthetic test soil that mimics blood and tissues found on surgical instruments can ensure that your equipment is functioning properly.
The VERIFY Ultrasonic Indicator provides an independent objective test to evaluate the ultrasonic cycle. Problems such as insufficient energy, water level, improper temperature, and degassing may impact the results.
Residual Protein Test - A residual soil analysis looks for the presence of bioburden that may remain on instruments that have completed the cleaning process. Samples collected from instrumentation are chemically evaluated, and the detection of residual protein shows can indicate that the cleaning process was not successful.
VERIFY RESI-TEST Cleaning Indicators detect the absence or presence of protein and protein residues with a sensitivity of ≥ 1μg. Cleaning verification is provided by collecting a sample from the device. Both cleaning indicators are intended for use after manual or automated cleaning and prior to high level disinfection or sterilization. Easy-to-read results are available in just five seconds.
All staff using the ultrasonic cleaner should follow policies and procedures for operating an ultrasonic cleaning unit. The facility should develop policies and procedures based on the manufacturer's owner's manual and IFUs for the equipment.
Best practice in SPDs for ultrasonic cleaning must be stated in written policies and procedures, as recommended by AAMI: "The health care organization should establish policies and procedures for all methods of cleaning and decontamination of reusable items." (ANSI/ AAMI ST79:2017 7.2; Policies and Procedures).
Daily and preventative maintenance procedures should be in place to ensure the ultrasonic cleaning unit is in optimal working order for the expected performance. Daily maintenance procedures can be found in the manufacturer's IFUs. Some examples might include proper cleaning of the ultrasonic unit's exterior surface, internal surfaces of the tank, and the drain screen.
An ultrasonic preventive maintenance program that the facility designs should follow the manufacturer's recommendation as to how often preventive maintenance is to be performed. These regular maintenance programs should include adjustments and replacements of worn parts so that untimely or costly schedule interruptions can be avoided. The maintenance records should be available for the department, surveying bodies, facility operations, biomedical department, and maintenance department, depending on your facility's organization.
As surgical and reusable medical devices evolve in complexity, the need for proper cleaning equipment is essential to the SPD. Ultrasonic cleaners are one piece of equipment that can assist in this process.
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1 American National Standard/ Association for the Advancement of Medical Instrumentation. (2017). ANSI/AAMI ST79:2017 Comprehensive guide to steam sterilization and sterility assurance in health care facilities. Arlington, VA: Author.
2 American National Standard/ Association for the Advancement of Medical Instrumentation. (2017). ANSI/ AAMI ST90:2017 Processing of health care products – Quality management systems for processing in health care facilities. Arlington, VA, Author
3 Association of periOperative Registered Nurses. (2020). Guidelines for perioperative practice. Denver, CO: Author.
4 Association for the Advancement of Medical Instrumentation (2014), AAMI TIR34:201 Water for the reprocessing of medical devices. Arlington, VA, Author
5 Centers for Disease Control and Prevention. (2019) Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008. https://www.cdc.gov/infection-control/about/index.html?CDC_AAref_Val=https://www.cdc.gov/infectioncontrol/pdf/guidelines/disinfection-guidelines-H.pdf%2520downloaded%252011/23/2020
6 Occupational Safety and Health Administration (OSHA) (2020) Electronic Code of Federal Regulations– Bloodborne Pathogens 1910.1030 https://www.osha.gov/laws-regs/regulations standard number/1910/1910.1030downloaded 11/23/2020G
7 McDonnell and D. Sheard (2012) A Practical guide to Decontamination in Healthcare: Pondicherry, India. SPi Publisher Services.