INSTRUMENT STERILISATION AND DECONTAMINATION


Expert guidance on the optimal sterilisation process


IHEEM-registered AE (D), Dr Brian Kirk, explains the importance of using validated sterilisation processes to produce sterile single or multi-use medical devices such as re-usable metal surgical instruments, and the internationally agreed standards covering the sterilisation process and steriliser equipment. He considers both high and low temperature processes, and the key considerations when investing in sterilisation technology, and when faced with the challenge of a new medical device which requires sterilisation.


Sterile medical devices must be sterilised in a validated sterilisation process. The objective of any such process is to produce a product free of viable microorganisms. There are a variety of such sterilisation processes available, some of which are shown in Figure 1. Figure 1 shows sterilisation processes which achieve microbial inactivation by a physical process, and those that do so via the action of a microbicidal chemical agent. Physical processes can be sub-divided into those which take place at a high temperature (e.g. 121-138 °C) and those at a low temperature (room temperature to 80 °C). Processes achieving microbial inactivation using a microbicidal chemical


usually employ oxidising agents such as hydrogen peroxide or alkylating agents such as EO (ethylene oxide). These processes almost invariably take place at lower temperatures (room temperature to 80 °C), and are often described as low temperature sterilisation (LTS).


High temperature processes In a healthcare setting, the majority (ca 90%) of reusable sterile medical devices will be sterilised at high temperatures and pressures in moist heat sterilisation processes employing saturated steam. The majority (ca 90%) of single- use medical devices produced by the medical device industry will be sterilised


Sterilisation Processes


Mechanical Removal (Filtration)


Physical Hot


Moist heat (steam)


Dry heat Cold


Ionising radiation UV light


Gamma e-Beam


Chemical


Oxidising agents H2


H2 Alkylating agents O2 O2 O2 vapour vapour


with plasma H2


with ozone Chlorine dioxide


Peracetic acid vapour with plasma


Ozone gas Figure 1: Processes used both in industry and healthcare for sterilisation of medical devices. October 2022 Health Estate Journal 35 vapour


Ethylene oxide LTS with


formaldehyde Glutaraldehyde


in a low temperature sterilisation process, commonly using irradiation with ionising radiation (e.g. gamma), or using ethylene oxide gas sterilisation (EO). However, the industry is actively investigating alternative low temperature processes such as those employing vaporised hydrogen peroxide (VH2O2) as an alternative to EO. There are many International and


European standards (implemented as British Standards), and locally produced guidance for both sterilisation processes and sterilisers. In the UK, each of the four home nations will have produced its own guidance, broadly similar, as Health Technical Memoranda (01-01). Table 1 lists International and European standards


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