DECONTAMINATION
Chemical additives that can be absorbed into, or adsorbed onto, surfaces of the WD (for example, plastic pipework) may be carried over into subsequent stages of the process.11 This choice of process chemicals should be in line with those tested by the WD manufacturer with supporting evidence of efficacy. HTM 01-06 recommends that the WD manufacturer should offer at least three different disinfectants and detergents suitable for their WD. The selected disinfectants/ detergents must be compatible with the devices being reprocessed. For example, flexible-endoscope manufacturers will advise on additives that may cause damage to their equipment. Use of such additives may invalidate any guarantee and cause irreparable, or very expensive damage, to the endoscope or accessories.
Chemical damage can occur in areas that are not visible when checking the scope e.g. internal lumens. This means there needs to be assurance that the endoscope materials do not deteriorate, as this will increase the possibility of bioburden forming which would be detrimental to patient safety. Many endoscope reprocessing units have endoscopes from several manufacturers, so it is essential that information is obtained from the endoscope manufacturers with regard to chemicals that are known to be compatible with their range of equipment.
Some detergents/disinfectants designed for WD use have added corrosion inhibitors, as water itself is corrosive if the hardness is less than eight. However, some disinfectants may contain no corrosion inhibitors at all, which in the longer term could lead to damage of the endoscope and/or the automated reprocessor. This damage usually
The BSG recommends that a guiding principle for decontamination is that ‘any patient must be considered a potential infection risk, and each endoscope and device must be reprocessed with the same rigour following every endoscopic procedure’. This is a principle which is just as relevant to reprocessing in the COVID era.
takes place over a period of time and is not immediately obvious. It is very important when comparing disinfectants or detergents, to remember that having a comparable active compound is not the same as having the same formulation. For example, PAA based disinfectants may all appear to have similar formulations, but peracetic acid is formulated from PAA, acetic acid and hydrogen peroxide dissolved in water, at various concentrations. Different commercial solutions are likely to contain different concentrations of these three chemicals.
A disinfectant marketed as containing
PAA may look like PAA but is not necessarily the same product and is likely to differ in the product details. Even if it appears to contain the same ingredients, the actual formulation may vary considerably. All of which may impact on the product stability and subsequent shelf life, as well as affecting the duration of contact. A fast acting PAA with a short but effective contact time means quicker reprocessing, saving valuable time. The rate and intensity of the reaction between the PAA and the soil on the
endoscope shows a wide variation. Although the pH of PAA can be around 2 which is highly acidic, it can be buffered to a pH of four or even eight. The temperature at which the PAA is used, together with the pH of the product has a significant impact on the deactivation of pathogens. For example, a PAA used at a temperature of 15 degrees C and with a pH of 7 will require five times more PAA to deactivate pathogens than a pH of 7 used at a temperature of 35 degrees C. Material compatibility tests are performed on test pieces or on complete endoscopes using the detergent and the disinfectant alone and in combination. Manufacturers of process chemicals, endoscopes, and EWDs should provide information about material compatibility. Any kind of deposition can be of concern for microbiological growth.2 It is important that the correct type of chemical is used for the appropriate application. For cleaning critical equipment, such as endoscopes, the choice is between enzymatic or non-enzymatic detergents (not all neutral detergents are non-enzymatic). Compared with enzymatic detergents,
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