The foundation of sterilization is cleaning. How can we be sure that the mechanical cleaning equipment being used is producing clean medical devices?
There are methods available to verify that the mechanical equipment used to clean medical devices is functioning appropriately. ANSI/AAMI ST79:2017 Comprehensive guide to steam sterilization and sterility assurance in health care facilities (ST79 Steam sterilization standard) and 2020 Amendments A1, A2, A3, A4 provide recommendations on routine verification testing of decontamination equipment.
Mechanical cleaning equipment used in the decontamination room are documented, reproducible, automated, or semi-automated systems that use both automated and manual cleaning processes and are validated for use. There are different types of equipment used, with the typical mechanical cleaning equipment being washer disinfectors, ultrasonic washers, and cart washers.
According to ANSI/AAMI ST79, verification testing should be performed on all mechanical cleaning equipment as part of the overall quality assurance program. Mechanical cleaning equipment should be tested upon installation, each day it is used, and after major repairs. When evaluating or changing to a new type of cleaning solution, all cycles used should be tested to ensure that the cleaning solution and action are effective. There are different methods to perform cleaning verification, with the following being the most common:
• Directly testing individual medical devices for residual soils (eg, adenosine triphosphate or ATP, protein, hemoglobin);
• Using a cleaning verification test device that provides a consistent and repeatable challenge to the cleaning effectiveness of the equipment;
• Monitoring critical parameters (eg, cycle printout) to evaluate the performance of the cleaning equipment.
Monitoring and verifying cleaning processes should be recorded. Some mechanical washers have digital readouts and cycle printouts that should be reviewed for each cycle and initialed by the operator to indicate an acceptable cycle. Most commercial cleaning verification products include record-keeping methods for use that may demonstrate the level or type of failure. Key performance outcomes include clean surfaces and adequate fluid flow in equipment that has adaptors for lumened devices.
Before operating any decontamination equipment, the manufacturer’s written instructions should be reviewed and followed for indications for use and operation, including loading practices such as having hinged instruments loaded in the open position; use of accessories; and cycle selection. Gross debris should be removed from the medical devices before undergoing mechanical cleaning; if not removed, they will circulate through the washer and deposit onto other devices, impeding the cleaning. For automated cleaning to be effective, all device surfaces should have contact with the cleaning solutions.
Washer disinfectors are typically used for handheld instruments and utensils. Some washer disinfectors include flushing devices for lumened devices. A washer disinfector reduces microbial contamination using a multistep method consisting of cleaning solutions, water temperature, rinsing, lubrication (some cycles), and drying. These washers clean via impingement, which is the spray-force action of pressurized water against instruments being cleaned to physically remove bioburden. This impingement is similar to a dishwasher in that the cleaning is dependent on a combination of the water temperature, detergent, and spray force to remove soil from devices being processed.
These washers use successive steps during the wash cycle. The first step is a cool prerinse to prepare them for the next cycle (cool water is used to prevent coagulation of proteins). The next step is at a higher temperature with detergent to maximize the effectiveness of the detergent activity. The third step rinses the debris and detergents from the instruments. Again, some washer cycles may include a lubrication cycle. It is important that all cycles perform/function effectively in order to achieve thorough cleaning.
Instrument washer racks and conveyor systems should be inspected daily. A visual inspection includes checking the spray arms and washer jets for obstructions such as debris, paper, and mineral build up, because these will hinder spray action and disrupt cleaning efficacy. Commercial cleaning verification devices should be used to confirm this cleaning action. To ensure all spinning arms are functioning properly, verification testing devices should be placed on each level of an otherwise empty shelf. The cycle is run, then upon completion of the cycle, the testing mechanism is evaluated according to the verification manufacturer’s instructions for use, and these results are then recorded.
Washer traps/screens at the bottom of the unit should be visually inspected for debris at least daily and cleared of obstructions. The detergent container should be checked to ensure detergent is available. The chamber walls should also be visually checked for any scaling, such as a white scale.
If a white scale is observed, it should be immediately removed with a descaler recommended by the equipment manufacturer. This white scale can fall on instruments and clog pumps, motors, and spray arms. If the washer has a printout, that printout should be reviewed and initialed after each use to ensure that the cycle has reached the expected parameters.
Cart washers were originally designed to clean transport carts. They function in a manner similar to washer disinfectors but on a larger scale. Spray arms deliver high-temperature water and detergent, and successive steps provide rinse water and hot air drying cycles. Cart washer equipment can also be designed to process rigid sterilization containers and instruments. If a cart washer is designed and used to clean sterilization containers and instruments, the same cleaning verification used for instruments applies to cart washers.
Ultrasonic cleaners may also be referred to as “sonic cleaners.” The term “ultrasonic” is an appropriate name for this type of mechanical cleaner. “Ultra” means beyond, and “sonic” means sound; they are used for fine cleaning—to remove soil from joints, crevices, lumens, and other areas that are difficult to clean by other methods. The cleaning action of ultrasonic cleaners is performed by the use of cavitation. Cavitation is the process in which low-pressure bubbles in a cleaning solution burst inward and dislodge soil from instruments. To produce cavitation, an ultrasonic wave passes through a liquid, which makes the liquid vibrate.
A hospital sonic cleaner can produce from 20,000 to 38,000 vibrations per second. The vibrations are transmitted through the detergent bath and create cavitation. With this process, ultrasonic waves pass through a cleaning solution, the molecules of the solution are set in very rapid motion, and small gas bubbles develop. As the bubbles grow larger, they become unstable until they implode inwards (not explode). Creating a vacuum in the solution draws minute bits of foreign material (including microorganisms) from cracks and crevices such as hinges and serrations on instruments. This vacuum action results in the cleaning of hard-to-reach areas. For this process to work effectively, the water must be degassed each time it is changed in the sonic cleaner. Excess bubbles in the water are formed during filling, and these gas bubbles reduce the energy released during implosion. The de-gas process involves filling the sonic cleaner, closing the lid, and running it for 5 to 10 minutes. Degassing should only be done after the tank is filled (not while it is being filled) to avoid damaging the equipment. Some ultrasonic cleaners will automatically de-gas the solution when the chamber is filled. As a safety precaution, the lid of the sonic cleaner should be closed at all times when the unit is operating to prevent aerosols from being dispersed.
An ultrasonic unit may have one, two, or three chambers. The first chamber is for the detergent bath, the second is for rinsing, and the third is for drying. Some single-chamber ultrasonic cleaners may only provide a cleaning process, whereas other single-chamber units perform both cleaning and rinsing functions. There are different types available, each with specific features intended for a specific purpose.
Basic ultrasonic washers.This is the simplest design, consisting of one or more chambers. Some models have automated processes consisting of several phases: filling with water, adding a cleaning agent, degassing, rinsing, and draining. Simpler models are completely manual, with the user performing all the functions of filling, rinsing, and draining.
Ultrasonic irrigators. This type is designed to clean minimally invasive surgical devices with lumens (flushing the inside of instruments as well as exterior surfaces). The cavitation process is used, with the addition of flushing and irrigation to remove the bioburden from lumens, channels, box locks, and other crevices. These types of ultrasonic cleaners contain water ports with hoses and special adapters to connect to various devices such as laparoscopic and robotic instruments.
Ultrasonic irrigator washers. These ultrasonically clean external surfaces and interior lumen channels using rapid-flow, high-pressure irrigation. This equipment provides programmable wash cycles.
Ultrasonic irrigator washer disinfectors. This equipment has programmable, automated ultrasonic cleaning processes. It cleans internal lumens and channels through high-pressure irrigation, detergent solution washing, optional lubrication, and thermal disinfection.
The solution temperatures for cleaning instruments should be between 80°F and 109°F (27°C and 43°C), unless otherwise specified by the equipment or detergent manufacturer. Temperatures above 140°F (60°C) will coagulate protein, making it more difficult to remove. Water should be changed when it is visually soiled—or at regular intervals—to prevent soiled particles from redepositing on instruments. The unit’s tank should be cleaned, and the drain should be checked for debris at each water change. The ultrasonic cleaning process lifts proteins, starches, and lipids from instruments; therefore, it is important to routinely clean the tank according to the manufacturer’s instructions. An ATP test can used to measure the tank’s cleaning effectiveness.
There are different types of sonic cleaners, and each function requires verification testing. A cavitation test is commercially available to test the cavitation energy, and soil removal verification tests are also available. For ultrasonic washers with irrigation capabilities, verification tests that test for channel irrigation should be used. If using multiple channel irrigation ports, each should be tested to ensure adequate flow.
Cleaning equipment is an essential step in the processing of medical devices. For that reason, this equipment should undergo cleaning verification to ensure it is functioning appropriately. ✥
Susan Klacik, BS, FCS, ACE, CHL, CIS, CRCST, AAMIf, is Clinical Educator for the International Association of Healthcare Central Service Materiel Management (IAHCSMM) and a Fellow of the Association for the Advancement of Medical Instrumentation (AAMI).
Association for the Advancement of Medical Instrumentation. ANSI/AAMI ST79:2017 & 2020 Amendments A1, A2, A3, A4. Comprehensive guide to steam sterilization and sterility assurance in health care facilities.
International Association of Healthcare Central Service Materiel Management. Central Service Technical Manual, Eighth Ed. 2016.