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Central Service - Issue 4/1999

Central Service - Issue 4/1999



M. Hornung*, U. Junghannß:
Assessing the Cleaning Performance of Washer-Disinfectors
(Zentr Steril 1999; 7 (4): 221-233)

Within the framework of a thesis, a method was devised which allows objective assessment of the cleaning performance of washer-disinfectors. This method might be able to bridge the gap still existing between, on the one hand, optical inspection - which proves to be inadequate - and, on the other hand, the exact evaluation of the cleaning performance required for validation. The method being presented here is based on the following consideration: if the cleaning performance of a washer-disinfector is sufficiently intensive to duly meet the test requirements addressed to it, then based on the state of the art it can be deemed to be optimised.
The new method is based on a process challenge device (PCD) that reflects field conditions, with a suitable test soil and a procedure for quantitative determination of the test soil. The challenge device takes account of the design features of real surgical instruments which are of relevance when cleaning. BAMS was chosen as test soil. Quantitative determination of any test soil residues remaining on the challenge device after cleaning was performed by means of absorption measurement in the ultraviolet range, once the test soil residues had been eluted in a multi-step procedure.
Following experiments conducted with two newly installed washer-disinfectors, a mandatory requirement was formulated for the cleaning performance. This requirement stipulated that the cleaning programme should remove at least 87% of the applied test soil. If this stringent requirement is not met, adjustments have to be carried out on the washer-disinfector undergoing testing. The method presented here surely needs to be improved. This can only be achieved by further experiments focusing primarily on optimisation of the test soil elution from the challenge device.
Key Words
Washer-disinfector, cleaning performance, validation, process challenge device, test soil


R. Reichl*, K. Roth, P. Heeg, G. F. Bueß:
Requirements Governing Washer-Disinfectors for Surgical Instruments
(Zentr Steril 1999; 7 (4): 234-239)

Just as the array of reusable instruments currently used in the clinical setting is composed of instruments reflecting very divergent states of the art, so stringent are also the demands being made on a universally deployable washer-disinfector for processing all instruments. The forward pressure and volume flow are closely related and must be sufficiently high to assure efficient cleaning. A check of the flow rate of each instrument or component with lumen to be cleaned is indispensable. Furthermore, two-phase flow and sonication can considerably enhance cleaning. The microbiological requirements for washer-disinfectors are being compiled by CEN in TC 102 WG 8. The "General Requirements" have been put forward as prEN. An automatic process, which is based on defined cleaning, disinfection and drying cycles, is a precondition for a validated process. This also includes online parameter monitoring and documentation.
Only very few of the washer-disinfectors available on the market presently meet all the aforementioned requirements. Based on the state of the art, the development and construction of such a washer-disinfector is no longer a problem. Of course the price plays a major role as regards the user's decision on what to buy and hence also in the strategic decision-making on the part of the manufacturers of washer-disinfectors. But adopting a responsible approach to processing, no attempts should be made to skimp on investments in critical areas of the hospital, such as instrument processing, despite increasing cost pressure.
Key Words
washer-disinfectors, processing, minimally invasive surgery, surgical instruments

T. Miorini*, V. Buchrieser:
Small Steam Sterilisers in the Light of Standardisation Drafts
(Zentr Steril 1999; 7 (4): 240-247)

For some time now, there have been European standard drafts available for small steam sterilisers (prEN 13060 Part 1-4). These introduce a number of new requirements for the design, monitoring, documentation and performance of equipment. By classification into three different device types (B, N and S), specification will in future be a decisive factor when deciding what to buy.
Since processes must also be validated for small steam sterilisers, questions arise as to the spatial, personnel and organisational requirements in homes for the elderly and nursing homes, doctors' surgeries and other small sterilisation units.
Key Words
Small steam steriliser, validation, requirements for sterilisers, EN 13060


P. Heeg:
Series on Infectiology - Infections by Pathogenic Escherichia coli


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