Guide to Ultrasonic Cleaning of Medical Devices: How Ultrasonics Work and More

What Is Ultrasonic Cleaning?

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.

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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.

How does an Ultrasonic Cleaner work?

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.

How an Ultrasonic Cleaner Works

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:

• Detergents
• Cavitation
• Flow/Sonic Irrigation

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.

Generation of Ultrasonic Waves

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.

Cavitation

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.

Flow and Sonic Irrigation

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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How To Use An Ultrasonic Cleaner For Surgical Instruments

Typical steps for using an ultrasonic cleaner for surgical instruments include:

• Visually inspect instruments for debris and manually clean them at the sink
• Instruments should be separated in batches by metal type because mixing metals within a solution causes metal ions to transfer between instruments, which can result in pitting and etching of the instrument surfaces
• Prepare an appropriate cleaning solution following the manufacturer's instructions:
  • Most modern ultrasonic cleaners in hospitals use an automated fill and dosing system
  • It is good practice to empty, clean, rinse, and dry the unit at least daily, or preferably after each use, as defined by facility procedures
• Load the ultrasonic cleaner, ensuring instruments are submerged but not overcrowded
  • Place instrumentation within a validated basket or on the ultrasonic cleaner's shelf. Instruments should not be placed directly on the bottom of the tank, as they might damage the transducers and scratch the tank surface. Follow the ultrasonic cleaner's instructions for instrument placement, including the maximum weight allowed.
• Connect any lumened instruments to flow ports, ensuring the tubing is not kinked, then follow the instructions of your ultrasonic cleaner to begin the cycle.
• Set parameters or select the cycle to be run

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.

Ultrasonic Cleaning Of Ophthalmic Instrumentation

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.

Cleaning Chemistries for Ultrasonic Machines

Beyond cleaning - selecting a suitable detergent for ultrasonic cleaning is an important consideration. The cleaning chemistry's formulation should be:

• Compatible with the cavitation process
• Effective over a range of different water qualities
• Low foaming
• Free rinsing
• Non-toxic and non-abrasive
• Effective for all soil types
• Preferably biodegradable

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.

Barriers to Ultrasonic Cleaning

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:

• Chrome-plated instruments: the mechanical vibrations remove the chrome-plating
• Power instruments: the internal parts can be damaged by fluid invasion
• Endoscopic lenses: the vibration can damage adhesive seals and delicate optic light cables of flexible endoscopes, fiber optic light cables, and some rigid endoscopes
• Delicate small instruments: vibrations can damage delicate fiberoptic, microsurgical, and lensed instruments
• Certain materials: cork, glass, rubber, wood, and chrome

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.

Quality Control Tests for Ultrasonic Cleaning

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.

Ultrasonic Cleaning Recommendations

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: 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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Related Resources

The purpose of this write-up is to provide clinical staff with details surrounding ultrasonic cleaning. In Sterile Processing, we are tasked with multiple IFU’s, parameters, and regulatory checklists. We want to provide you with the basics of what you need to know when it comes to ultrasonic cleaning.

How does ultrasonic cleaning work?

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Ultrasonic cleaning removes particulates by cavitation (bubbles) and implosion. Cleaners are used in conjunction with detergents and enzymatic cleaners. Waves of acoustic energy are transmitted in aqueous solutions and disrupt the bonds that hold particulate matter to surfaces.

Most instrument manufacturers recommend ultrasonic cleaning as the most effective way to clean instruments, particularly those with hinges, locks, and other moving parts. Ultrasonic cleaners are considered a Class 1 medical device by FDA. They do not disinfect or sterilize instruments; however, when used in conjunction with manual cleaning, sonic cleaning can enhance the cleaning process and increase the effectiveness of disinfection and sterilization.

The parameters include; cavitation, flow sonic irrigation, and detergents.

The ultrasonic cleaning process allows for scrubbing action to reach small crevices, irregular surfaces, and internal passages, without damaging the intricate device. Ultrasonic washers are designed to dislodge challenging soils from the surface and lumens on instruments and provide consistent cleaning results throughout the washer chamber.

Per AAMI ST79/ 7.6.4.3.3 Selection of Mechanical and Disinfection Equipment: there are several types of Ultrasonic cleaners:

1. Ultrasonic cleaning equipment

2. Ultrasonic irrigators

3. Ultrasonic irrigator washers

4. Ultrasonic irrigator washer-disinfector

When to test your sonic:

Per AAMI ST79/ 7.6.4.4.1 General Consideration

B) Perform cavitation testing daily whenever the equipment is in use. Per AAMI ST79/ Annex D3 Cleaning Verification Tests for Users: Verification Tests for Ultrasonic Cleaners

Top considerations for your ultrasonic

1. Test for cavitation in an ultrasonic bath

• Indication can be the physical measurement of visual assessment
• Test for Soil Removal (external) in Ultrasonic Bath
• Indication is visual assessment or absence of marker on coupon placed in the ultrasonic bath
• Test for soil removal (internal within lumens) in Ultrasonic Bath
• Indication is visual assessment or absence of marker on a coupon placed in the ultrasonic bath

2. Water change after each use

AAMI ST79/

7.6.4.4 Ultrasonic Cleaning Equipment

7.6.4.4.1 General considerations

Ultrasonic cleaning should be:

d) performed with fresh cleaning solutions; solutions should be changed after each use (a “use” should be defined in the health care facility’s policies and procedures); and

e) followed by thorough clean water rinsing or detergent washing to remove ultrasonic cleaning equipment bath residues and contaminants.

3. Critical water is recommended

AAMI Standards TIR34

5.2.1.3 Rinsing

Tap water is often adequate for rinsing and removing soil loosened by the cleaning process and for rinsing and removing detergent residues, provided that it meets the requirements for Utility Water. However, if the quality of the tap water could cause corrosion, tarnishing, or salt deposits, it might be necessary to use various water treatment processes (e.g., softening, deionizing) to ensure that devices are not damaged and the ensuing disinfection or sterilization process will be effective. For devices that will contact the bloodstream of other sterile areas of the body, the final stage in rinsing requires water that does not have excessive levels of organics (e.g., endotoxins or other microbial constituents); therefore, critical water is recommended.

Per AAMI ST79/

7.6 Cleaning

7.6.1 General Considerations

c) Devices should be thoroughly rinsed. If a basin is used, the rinse water should be changed after each use. The final rinse (mechanical or manual) should be with purified water (e.g., distilled or RO water). See TIR34 for recommendations on the use of critical water.

4. Not all ultrasonics reprocess the same

There are some ultrasonics that are validated for reprocessing da Vinci Endowrists. We validated the Skytron Flex for mixed loads in the same cycle. That means you can reprocess your da Vinci, Orthopedic, cannulated, and non-cannulated in the same 35-minute cycle which includes thermal disinfection and critical water final rinse.

Meet our Skytron Flex washer-disinfector

• Clean All Ultrasonic Approved Instruments in One Cycle: Versatile design with the ability to irrigate cannulated instruments such as the da Vinci products and non-cannulated instruments in the same cycle.
• The Flex ultrasonic instrument cleaner can wash and disinfect up to 125 pounds of instrumentation using your current ultrasonic trays. Includes up to 6 trays per cycle
• Achieve optimal disinfection standards: the Flex Ultrasonic surgical cleaner only irrigates with fresh water and detergent and drains contaminated water after each cycle.

What do our customers say?

“The Skytron Flex has been a lifesaver for our department. The efficiency of throughput and being able to sonicate and wash along with a thermal rinse cycle in less than 40 minutes has been a game-changer for us. Being able to process up to 24 robotic arms in one cycle as well as using our existing trays to place orthopedic items into the unit reduces overall throughput time in decontamination.”

See how Skytron’s Flex Ultrasonic Washer can assist in your surgical instrument cleaning protocol with this video https://youtu.be/Xvlgh_acrBU or learn more about product specifications here http://www.skytron.com/products/sterile-processing/flex-ultrasonic-washer-disinfector/

Disclaimer: The purpose of this article is to provide you with a broad knowledge of Ultrasonic cleaning. Proper device and instrument reprocessing requires strict adherence to IFUs, national standards, and professional society guidelines. Your facility should have its own copies of AAMI guidelines and equipment IFUs.

If you are looking for more details, kindly visit Medical Ultrasonic Cleaner.