The purpose of medical device cleaning validation is to assure that the medical device cleaning procedure consistently controls potential carryover, contaminants, cleaning agents and extraneous material into the device to a predetermined level which will not pose a risk to the patient and will meet cleaning validation acceptance criteria.
Based on regulatory requirements, equipment and medical devices should be cleaned and stored in a way that prevents contamination and cross-contamination which may risk patient health.
There are several aspects to be considered before the cleaning process is established; the desired cleanliness level, the cost of the cleaning agents and cleaning process, the risk of cleaning process residues, toxicity and cleaning agent safety and compatibility.
This article focuses on several medical device cleaning techniques, such as manual cleaning and use of an ultrasonic bath, and cleaning validation.
Preparation of a Medical Device Cleaning Process
After identifying, analyzing and assessing the risks involved with the use of the medical device and the subsequent required cleanliness level, a cleaning process should be developed and validated. There are several things to consider before validating a cleaning process:
- Required level of cleanliness
- Cost of cleaning agents and cleaning process (energy, time, labor and materials)
- Safety and compatibility of cleaning agents
- Risks to the patient posed by cleaning process residues
Manual cleaning is often used when automated cleaning processes (Clean in Place/ Clean on Place) cannot be implemented and/or may damage the medical device, or when small quantities of devices must be cleaned (for example, for medical devices that should be cleaned prior to being used in a clinical trial with few subjects).
Manual cleaning methods can include a combination of solvents, detergents, soaking, scrubbing, rinsing and washing under pressure and temperature. This type of cleaning incurs high labor costs and may lead to inconsistency due to lack of measurable or quantifiable cleaning process parameters and controls.
Manual cleaning methods cannot be validated properly, but may be used as an initial step of a multiple-stage cleaning process.
Medical Device Cleaning Using an Ultrasonic Bath
Use of ultrasonic baths for cleaning is common in the medical device industry for products like guide wires and metal parts, assemblies and implants. This method is usually used after devices have been initially cleaned to remove bulky impurities, particles and greasy material residuals. This method is designed to remove fine impurities only.
An ultrasonic bath may be used with water, detergent or solvents (such as ethanol) and operated at temperatures that vary from 15˚C to 140˚C. The detergent is to be chosen based on the physical and chemical characteristics of the impurities to be removed by the cleaning.
For organic impurities, alkaline detergent is suitable. For inorganic impurities, acidic detergent is suitable. The process may be followed by rinsing with purified water.
Ultrasonic cleaning processes for medical devices involve generating ultrasound waves at a frequency of 20–130 kHz to create cavitation bubbles that inflect force against contaminants adhering to or embedded in the surface of the medical device part.
At higher frequencies, the cavitation bubbles increase in number and decrease in size. Larger bubbles release more energy when they interact with the material. For smaller parts it is better to employ a large amount of smaller bubbles that are able to penetrate small areas.
Ultrasonic cleaning is suitable for devices with uneven or homogeneous surfaces that may “trap” impurities. Ultrasonic cleaning has the potential to cause significant damage to small medical devices like stents, specifically devices that react to a resonant frequency close to that used in the ultrasonic bath.
An ultrasonic bath cleaning method should include the following parameters:
- Ultrasonic frequency
- Ultrasonic power
- Cleaning time
- Cleaning agents
- Ultrasonic bath temperatures
- Quantity of parts/medical device to be cleaned per cycle
- Ultrasonic bath location (clean room classification)
- Drying procedure
Medical Device Washing and Disinfecting Machines
This type of multi-stage cleaning process comprises several stages which may vary, depending on the type of impurities to be removed by the cleaning and the desired level of cleanliness.
An example of a typical medical device cleaning cycle is washing with highly alkaline pH, followed by rinsing to neutralize the pH, then continuing with a highly acidic rinse solution and, finally, rinsing with purified water.
Cleaning of medical device sub-parts might necessitate additional soaking, enzyme incubation and ultrasonic treatment. The advantages of medical device cleaning using washing machines are that they use an automated process, are easy to operate, and usually minimize pre-treatment stages and labor.
Procedures and validation for use of an automatic washer should include the following parameters:
- Washing time
- Washing temperature
- Loading patterns
- Water quantity
- Acid and alkaline solutions
- Ultrasonic capabilities
- Critical parameters online monitoring (conductivity)
Medical Device Cleaning Validation
Per regulatory requirements, equipment and medical devices shall be cleaned in order to eliminate contamination and to minimize risk to the patient.
The purpose of medical device cleaning validation is to assure that medical device cleaning procedures consistently control potential carryover, contaminants, cleaning agent residuals and ingress of extraneous material into the device at a predetermined level which will be reflected in the cleaning validation acceptance criteria.
Medical device cleaning validation is to be performed based on an approved cleaning validation protocol. The cleaning validation should include worst case scenarios for medical device cleanliness level, shortened cleaning processes, etc.