Washer-disinfectors can be operated with three different programmes, with provision made for changing the programme controls during the various steps to suit the respective requirements. In addition, the washer-disinfector may have several permanently set programmes. The RKI programme was outlined in the last edition of Central Service. The following article now gives a general overview of the Vario programme and of a programme with a chemical disinfection step for heat-sensitive items.
Vario or Alternative Programme
The ever-increasing use of minimally invasive techniques and instruments (MIS) - the latter should ideally also undergo automated processing - has resulted in preference being given to an alternative programme control: VARIO PROGRAMME (fig.1). In this programme, thermal disinfection takes place in the final rinse. Hence it is possible to rinse first of all once or several times with cold water in order to remove all water-soluble residues, e.g. native blood. This considerably reduces the demands made on the detergent and the adverse effects generated on performance by foam-forming residues (blood) are minimised in the automated cleaning cycle. The actual cleaning step follows preliminary rinsing.
The DETERGENTS are selected on the basis of the materials used for the items being cleaned. Accordingly, neutral detergents, which may contain extra enzymes, are given preference for surgical motors and instruments with optics.
The TEMPERATURES and EXPOSURE TIMES in the cleaning cycle are tailored to the respective detergent. For example, for alkaline detergents temperatures of approx. 60 °C and exposure times of between 3 and 5 minutes are selected. Enzymatic detergents with proteases are able to derive maximum benefit from the enzymatic activity at around 40 °C and require accordingly longer exposure times which should be between 5 and 10 minutes. The manufacturer's special recommendations must be observed. The following table gives an overview:
||approx. 60 °C
||3 - 5 min|
|approx. 40 °C
||7 - 10 min|
|approx. 50 °C
||5 - 7 min|
Prolongation of the exposure time can greatly enhance the cleaning effect and, in the light of the total time needed for processing, plays hardly any role. It is often noted that after experiments and readjustments, the appropriate optimal temperatures and exposure times are not reset. The shortcomings manifest in the cleaning performance are compensated for by resorting to manual pre-cleaning or to use of ultrasound, possibly also because there is a fear of admitting these shortcomings and of incurring costs by consulting the customer service engineer.
Depending on the detergent, various types of water quality are required for the cleaning and rinse cycles. The rinse cycles follow the cleaning cycle. If alkaline detergents are used, a NEUTRALISING AGENT is added to the first rinse water. Detergent residues need not be neutralised if neutral detergents are used. Nevertheless, the addition of an acidic product (acid-based neutralising agent) to the first rinse cycle helps to prevent deposits, especially if the general water quality is poor (hardness and heavy metal contents).
Thermal disinfection with a temperature of 93 °C and a hold time of 10 min takes place in the final rinse. For this purpose, demineralised (supply unit) water must absolutely be used to prevent staining and corrosion.
Chemical-Thermal Processing Programme for Heat-Sensitive Items
The CHEMICAL-THERMAL PROGRAMME has to be selected if medical devices or utensils which tolerate a maximum of 60 °C have to be processed. Since the temperature of 60 °C even with a prolonged exposure time does not generate an adequate microbicidal effect, a SEPARATE DISINFECTION STEP must be appended to the cleaning cycle. Following the disinfection step, at least two rinse cycles take place in order to remove all residues, including disinfectant residues. In the case of medical devices which are to be used for patients without subsequent sterilisation, the final rinse must meet special microbicidal requirements. The rinse water must be free of Pseudomonas aeruginosa, legionellae and atypical mycobacteria.
Disinfectants for automated use must meet special requirements. They must be foam-free, easy to rinse and compatible with the detergent. The required microbicidal action must be certified in an EXPERT OPINION. Generally a bactericidal, fungicidal, tuberculocidal and virus-inactivating action, e.g. including HBV, is required for processing heat-sensitive medical devices such as flexible endoscopes. From the Expert Opinion it must be possible to conclude with what concentration, temperature and exposure time the requirements are met. The requirements are preferentially met using aldehyde-based disinfectants.
Even washer-disinfectors that have undergone a type test are checked for problem-free functioning after installation and technical commissioning. In this course of this test it is established whether the required performance can be achieved with the associated tray inserts, also using the operating water available in the individual case and with the programme set and the products being used in the given concentrations and with the instruments and utensils to be processed with the normal load or tray arrangements. This ACCEPTANCE TEST will in future be the base for validation and must be organised by the operator. Performance is confirmed in tests to be conducted twice yearly and during running routine tests. Until recognised European test methods have been published, tests in Germany are carried out with open (not welded-in or otherwise enclosed) bioindicators based on the instructions from the Robert Koch Institute (RKI).
with kind permission of|
What programmes are there for washer-disinfectors?
VARIO PROGRAMME denotes a programme with thermal disinfection in the final rinse. Several preliminary rinses with cold water remove all water-soluble residues. Hence fewer demands are made on the detergent.
THE DETERGENTS used preferentially for surgical motors and optics are neutral products.
THE TEMPERATURES and EXPOSURE TIMES are selected on the basis of the detergent.
A NEUTRALISING AGENT is added to the first rinse water to neutralise the residues of the alkaline detergent solution. When using neutral detergents, addition of an acidic product in the first rinse cycle prevents formation of deposits.
THE CHEMICAL-THERMAL PROGRAMME is suitable for processing medical devices that can tolerate a maximum temperature of 60 °C.
A SEPARATE DISINFECTION STEP must be appended after cleaning, because the temperature of 60 °C even with prolonged exposure does not generate adequate microbicidal action.
THE EXPERT OPINION for a disinfectant must attest to the microbicidal action. Concentration, temperature and exposure time at which the requirements are met must be specified.
THE ACCEPTANCE TEST of a washer-disinfector must be conducted under the normal individual conditions and with the normal individual load. This test is the basis for validation.