The standard prEN 15883 "Validation of Washer Disinfectors" outlines requirements for washer-disinfectors and the process as well as test methods. Here the cleaning performance plays a pivotal role. In this STANDARD it is presupposed that during the cleaning step the washer-disinfector provides for adequate detachment, dissolution and removal of typical soils.
The updated GUIDELINE OF THE ROBERT KOCH INSTITUTE "Hygiene Requirements for Processing Medical Devices" even calls for medial devices that are free of any residues, as otherwise disinfection and sterilisation could be impeded. It is, however, obvious that it is not possible to achieve a state where absolutely no residues remain.
A small survey conducted by the Quality Task Group revealed that some instruments are not being properly cleaned even in washer-disinfectors with optimal settings. This is attributable either to the design of the instrument or to the nature of residues and to the degree to which they have dried. Such "problem-causing instruments" can vary depending on the medical discipline and on the way they are used. Below we give examples of processing for some disciplines and instrument groups.
Clips for compression of vessels on the scalp: these small micro-tweezers are applied with an application forceps. The clips cannot be dismantled. The branches may be as small as 1 - 2 mm. Blood becomes encrusted in the clips and is therefore difficult to remove.
Trepans for drilling a hole through the skull: blood and bone meal compromise their functionality. The material begins to cake due to the heat generated while drilling, thus hampering the cleaning process.
Residues become very dry because of the long operations - often lasting up to 10 hours. The curettes are covered in blood that has dried out. This could possibly be prevented by placing them in a detergent desinfectant that protects the material. Contrast media (blue fluid) and mucosal disinfectants also cause problems because both result in fixing of proteins. Speculas are not adequately cleaned in some cleaning processes. Efforts were made to overcome this by using special inserts in which they are placed separately and easy to reach. Furthermore, the dried mucous was not removed by neutral detergents.
Bone cement, e.g. for operations on the hip joint, cannot be removed even mechanically once it has dried, not to mention in a washer-disinfector. The dishes in which the cement was mixed must be wiped out immediately after use otherwise they will have to be discarded. Bone files must be freed of bone meal and splinters for example in an ultrasonic bath. Then they can be washed and disinfected in a washer-disinfector. Bone splinters that become detached in the machine could block nozzles and bring to a standstill the movement of a rotary arm. Intramedullary reamers are rinsed through manually and then washed in an ultrasonic bath. If an MIS carrier is available, it can be connected and mechanically processed. Pre-cleaning in the operation theatre is vital here. Screws, drills or screwdrivers with lumens for a guidewire (Ø approx. 1.5 to 2 mm) can be very difficult to clean in the washer-disinfector because they have no connection for a special similar trolley. They must therefore be rinsed manually and cleaned in an ultrasonic bath, followed by cleaning and disinfection in a washer-disinfector.
Any residual soils present in instruments that cannot be dismantled and in instruments that have no cleaning adapter can become detached or be released during sterilisation. Based on present-day knowledge, these instruments cannot be reliably processed. MIS instruments can be automatically cleaned and disinfected only in special carriers, because only in such cases is provision made for adequate circulation of the detergent solution and hot water for disinfection purposes. Despite this, manual pretreatment is often recommended, e.g. rinsing and brushing with special brushes (pipe cleaner) and use of compressed air.
Instruments for closing vessels:
Mono- and bipolar instruments have almost always denatured blood on their tips which cannot be removed during automated processing. Placing the instruments in a 3% hydrogen peroxide solution during surgery and wiping them off from time to time have proved useful. Surgical staff are very familiar with this method because it is continuously practised during surgery to preclude functional impairment due to caking of blood. This should be done even after surgery so as to facilitate cleaning in the CSSD. Once the blood has dried, these instruments can be cleaned in the CSSD only with a tremendous effort and time investment. This phenomenon applies to all instruments exposed to coagulation. Cleaning the smooth surfaces of bipolar forceps is also an onerous task, with the forceps coatings proving to be a particular problem. Blood penetrates the material at the transition to the insulation and is very difficult to remove manually. It is hardly possible to clean the grooves of clamps.
Ointments and tamponades are commonly used in the ENT setting. Often the nasal ointments have very high melting points, hence they cannot be emulsified during automated cleaning at temperatures of 60 °C or less. They dissolve in the Vario programme during subsequent disinfection at temperatures of over 80 °C and spread out over the other instruments and the chamber. The only remedy here is manual processing with wiping or to use what is known as the RKI programme (see Recommendation No. 11). Furthermore, it must be pointed out that some products result in fixing of blood and can damage instruments due to their corrosive properties.
Proposals for solving problems
What can be done with these items that are demonstrably difficult to clean? They are subjected to manual pre-cleaning as described above, e.g. in an ultrasonic bath. Hence in the case of these instruments part of the automated processing procedure is omitted. Strictly speaking these pretreatment tasks cannot be validated. In the context of quality assurance, these pretreatment tasks must be defined for the specific instrument in working instruments.
Disruptions caused by pretreatment tasks
Manual and ultrasonic pretreatment tasks can lead to disruptions in the ensuing automated process and lead to ad absurdum where a validated process is concerned. Such forms of pretreatment can have particularly negative effects when used with aldehyde-based disinfectant solutions if they result in COAGULATION OF PROTEIN, which cannot be removed during processing. If this takes place in lumened instruments, it may not be noticed.
Another common source of interference is entrainment of foaming surfactants during the automated process. Due to FOAM FORMATION in the washer-disinfector the mechanical action is impeded or brought to a standstill. Nor is heat conduction assured due to air bubbles, hence disinfection is jeopardised.