Cleaning processes before sterilisation

Ultrasonic cleaners are an optional pre-cleaning step that use high-frequency sound waves to create microscopic bubbles in water. These bubbles rapidly form and collapse (a process called cavitation), producing energy that helps dislodge dirt and contaminants from medical devices. This section incorporates relevant content from AS 2773:2019 Ultrasonic cleaners for health service organisations, which sets out the requirements and recommendations for safe and effective use of ultrasonic cleaners.

Ultrasonic cleaning is not a complete cleaning process – it does not remove all debris and does not provide thermal disinfection.

Therefore, items need to be promptly transferred to a washer-disinfector immediately after the ultrasonic cycle for thorough cleaning and thermal disinfection. Delays can allow loosened contaminants to redeposit on device surfaces. Only after this step can items proceed to packaging and sterilisation. Timely progression through the cleaning cycle ensures items are appropriately decontaminated and safe for reuse.

Ultrasonic cleaners are efficient and effective in pre-cleaning, but they are not suitable for all items as they may damage some materials, such as soft plastics, rubber, metallic instruments with poor-quality chromium plating, and mirrors. Check the manufacturer’s instructions for each reusable medical device.

Ultrasonic cleaners are best suited to cleaning:

• delicate instruments or those with joints or serrations
• high-quality stainless-steel instruments with good chromium plating
• rigid materials, such as some metal and glass items (check device’s instructions for use).

Ultrasonic cleaners are not suitable for cleaning:

• internal surfaces of cannulated reusable medical devices
• plastics and other similar materials
• cemented glass syringes
• mirrors and lenses (these will be damaged if repeatedly subjected to this process)
• fine-pointed reusable medical devices (the vibration caused by the process can blunt fine points).

Before using ultrasonic cleaners, always check the manufacturer’s instructions for use of each reusable device to confirm compatibility with ultrasonic cleaning.

⚠️ Never immerse fingers or other body parts into an operating ultrasonic tank. The energy produced can damage tissues and cause long-term joint injury. A warning label should be present on the cleaner.

Method

Only staff who have received appropriate training in the use, testing and maintenance of ultrasonic cleaners should operate the equipment.

When using ultrasonic cleaners:

• follow the manufacturer’s instructions for both the cleaner and the devices being cleaned
• degas the solution after filling or refilling the tank to help ensure effective cavitation by removing trapped air
• use cold water first, then add the recommended cleaning agent compatible with both the ultrasonic cleaner and the device materials.
• keep the solution temperature between 20°C and 40°C. Do not exceed this range.
• visibly soiled instruments need to be dry-wiped, damp-wiped, or rinsed before placing them into the ultrasonic cleaner
• instruments need to be placed in a single layer in a dedicated basket; do not stack or overload the basket
• the solution needs to be replaced before the next use if it becomes cloudy or visibly dirty.

Advantages and disadvantages to ultrasonic cleaners

Ultrasonic cleaners are not a requirement in general practice – they are an optional precleaning step. Table 10.14 outlines the advantages and disadvantages for using an ultrasonic cleaner in general practice.

Table 10.14 Advantages and disadvantages for using an ultrasonic cleaner in general practice

Maintenance monitoring of ultrasonic cleaners

Practices that use ultrasonic cleaners need to establish and document routine maintenance, testing, and monitoring procedures, including:

• daily function testing before use is required, preferably using a validated commercial test device that changes colour to confirm sufficient energy
• emptying and cleaning the cleaning tank at least once per day of use
• changing the cleaning solution daily or more often if it becomes cloudy or visibly soiled
• always degassing the solution when refilled, before processing instruments
• keeping the lid closed during operation to minimise aerosol release and noise.

Daily logbooks should include records of:

• solution changes
• degassing
• test results and maintenance
• the name of the person performing each check.

Automatic washer-disinfectors are considered best practice for cleaning reusable medical devices prior to sterilisation, as they provide a consistent, validated, and efficient method of cleaning and thermal disinfection, reducing the variability and potential errors of manual cleaning and supporting effective sterilisation and patient safety.

Washer-disinfectors operate by combining:

• high-temperature water cycles
• specially formulated alkaline detergents.

This controlled, automated process delivers mechanical cleaning action and thermal disinfection, ensuring a high level of decontamination before sterilisation. It is important to note that washer-disinfectors do not achieve sterilisation; sterilisation still needs to occur in a dedicated steriliser.

Key considerations for using washer-disinfectors:

• Items processed in a washer-disinfector do not require additional rinsing or drying before packaging for the steriliser.
• Manufacturer instructions must always be followed for correct operation and load configuration.
• Cycle monitoring is essential. Variables such as temperature, cycle duration, and detergent concentration need to meet validated requirements. Loads that fail to meet these criteria need to be reprocessed before sterilisation.
• Washer-disinfectors require regular servicing, maintenance, calibration, and validation to ensure ongoing effectiveness.
• Domestic dishwashers are not suitable and are not to be used for reprocessing medical devices.