The Principles of Medical Device Decontamination

Manufacturers will provide information about the medical devices which can be processed. Generally simple devices will be able to be processed in shorter cycles (ca 30 mins) compared to more complex devices such as endoscopes which will require a much longer processing time (ca 3 hours). Sterilizers Vaporised Hydrogen Peroxide (VH 2 O 2 ) sterilizers for use in hospital settings are typically free-standing units that require minimal infrastructure or complex services to operate. The sterilizers generally feature chamber capacities ranging from 200 to 500 litres. The sterilant is commonly supplied as a concentrated solution of H 2 O 2 (ca 59%) in water, with added stabilisers. The solution is usually in a single or multi-shot disposable container or in a cassette based system with sufficient VH 2 O 2 for one sterilization cycle per pod and several pods per cassette.

Chemical Methods – Low Temperature – Alkylating Agents

Figure 1 shows a number of sterilization methods using chemical agents which bring about microbial inactivation by alkylation of the vital molecules found within the cell. The mechanism of alkylation involves a short chain organic chemical binding to the cell molecules, or the micro-biocidal agent binds two of the cell molecules together so that they cannot function. Glutaraldehyde Whilst not a sterilization process in the sense commonly used (i.e. use of a micro- biocidal vapour in a sealed chamber with medical device loads wrapped in a sterile barrier system), glutaraldehyde has been used in liquid form for use in very specific situations. It is a toxic chemical which if mishandled can lead to acute and chronic health conditions in operators such as respiratory sensitisation. It was once used in open baths for decontamination of endoscopes which is rarely seen today. Ethylene Oxide Ethylene Oxide (EO) is termed an oxygen bridge molecule. The internal chemical bonds are strained making it highly reactive and able to form alkyl hydroxy bridges between biologically active cellular molecules. The process variables for an EO process are temperature, time and EO gas concentration in the presence of moisture as humidity.

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