Cleaning processes before sterilisation
Effective cleaning to remove all organic matter and other soiling is essential for ensuring successful sterilisation. If items to be sterilised are not cleaned thoroughly, adherent soiling can protect microorganisms from the action of the sterilisation cycle. If any matter is allowed to dry or harden on the item, the cleaning process will be more difficult and may be compromised. If an item cannot be cleaned due to its shape (eg narrow lumen), effective sterilisation cannot be guaranteed.
The sequence before sterilising involves initial treatment (above), optional pre-cleaning using an ultrasonic cleaner, then cleaning in an automatic dishwasher–disinfector (best practice) or by manual cleaning (not best practice). Some automatic dishwasher–disinfectors include an initial ultrasonic cycle (Table 10.5. Advantages and disadvantages of washing and drying devices used in reprocessing of reusable medical devices).
Manual cleaning is no longer acceptable as a method of pre-cleaning before sterilisation, except where specified by the manufacturer of a reusable medical device. Manual cleaning should only be used for pre-treatment before using a washer-disinfector, or if the practice does not yet have a washer-disinfector.
Pre-cleaning with ultrasonic cleaners
Ultrasonic cleaners pass ultra-high frequency sound waves through water, creating microscopic bubbles which implode, causing high-energy vacuum and movement (cavitation). Cavitation pulls dirt and contaminants from the surfaces of the items being cleaned. Therefore, before packaging for sterilisation, items must immediately be thoroughly cleaned after the cycle to avoid redepositing of matter, either by thorough rinsing followed by manual cleaning (including scrubbing), or using a washer-disinfector (if the practice’s washer-disinfector does not provide an ultrasonic cycle).
Ultrasonic cleaners are efficient and effective in pre-cleaning, but they are not suitable for all items as they may damage some materials (eg 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 used for delicate instruments, difficult-to-clean instruments such as jointed and serrated stainless steel instruments.
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).
When using ultrasonic cleaners:
- operate according to the manufacturer’s instructions
- items with gross residual soil must first be dry-wiped, damp-wiped, or rinsed in warm water before immersion into the ultrasonic cleaner
- items must form only one layer in the machine – they must not be placed on top of other items and the basket must not be filled
- the solution must be changed before the next use if it has become cloudy.
After removing items, they must be cleaned using one of the following methods:
- Place in an automatic instrument washer–disinfector
- Rinse under running warm water and then scrub manually (see manual cleaning). Wear an apron or gown and face shield during rinsing.
Maintenance monitoring of ultrasonic cleaners
Testing of the ultrasonic cleaner is required every day. This involves filling and degassing according to the manufacturer's instructions. Degassing is necessary after each fill, before instruments are processed.
The use of commercially available validated cleaning verification products is recommended. These use a colour change to indicate that the ultrasonic cleaner is supplying sufficient energy and conditions are correct. Alternative non-validated methods, such as the aluminium foil test or pencil test, are complicated and difficult to perform correctly.
The machine must be emptied, degassed, cleaned and dried at the end of each day of use, in accordance with the manufacturer’s instructions for use.
Practices that use ultrasonic cleaners must refer to the manufacturer’s instructions.
Record testing, solution changes and degassing in a log.
The use of automatic washer-disinfectors to clean reusable medical devices before sterilising is now considered to represent best practice, in preference to manual cleaning or ultrasonic cleaning.
Automatic washer–disinfectors use high temperatures and alkaline detergents to clean reusable medical devices. They clean and disinfect (by heat), but do not sterilise.
Their use is preferable to manual cleaning because the process can be validated by objective measures of temperature reached, time at temperature, and cleaning parameters. It also avoids operator contact with contaminated solutions and sharps.
Items that have been subjected to a washer-disinfector cycle do not require further rinsing and drying before being packaged for the steriliser.
Small benchtop or under-bench models are suitable for general practice. Cycles typically take 35–50 minutes.
Practices that use washer disinfectors must refer to the manufacturer’s instructions for their appropriate use.
Washer-disinfector cycles must be monitored to ensure that the required variables have been achieved. If not, the load must be failed and the items reprocessed before a steriliser cycle.
Washing/drying devices need regular servicing, maintenance, calibration and validation.
Domestic dishwashers, while similar, are not suitable for washing reusable medical devices and must not be used for this purpose.
⚠ When handling soiled devices, staff must use personal protective equipment, including long-cuffed, chemically resistant gloves, eye protection (eg full face shield), and apron/gown, as appropriate.
It is not appropriate to limit pre-cleaning to manual cleaning, unless validated instructions provided by the manufacturer of a reusable medical device specifies this (eg for a very delicate item that cannot be machine-cleaned). Automatic cleaning is recommended as best practice. Manual cleaning should only be used for pre-treatment before using a washer-disinfector, or if the practice does not yet have a washer-disinfector.
Manual cleaning involves the following steps:
- Fill the designated ‘dirty’ sink or bowl with warm water and dilute instrument-cleaning detergent.
- Scrub all used devices (even those not visibly soiled) under the surface to reduce generation of aerosols.