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4. Even in the best equipped units with fully automated, enclosed cleaning

systems, accidental spillage may occur.

5. Measurement of atmospheric aldehyde levels, particularly at low

concentrations, is difficult. The only reliable method involves the use of

impregnated filters followed by assay using high performance liquid

chromatography (27).

It is possible that within the next few years the use of aldehydes will be reduced

because of these difficulties and safe alternatives are being sought. These

alternatives must be at least as effective a disinfectant as glutaraldehyde, be

non- damaging to endoscopes, accessories and processing equipment, be nonirritant

and non-sensitising to users and should not be expensive. As yet no

agent completely satisfies these ideals and it is possible that such a disinfectant

will not be found. Almost certainly adequate ventilation and other protective

measures will continue to be required for most, if not all. instrument disinfectants.

The recent introduction of automated disinfection machines that use

glutaraldehyde in very low concentrations has the potential for reducing the

exposure risk to staff. The effectiveness of glutaraldehyde in these machines is

maintained by heating acid based formulations to 45° - 55°C and the use of fresh

materials for each cycle reduces the possibility of contamination and cross

infection. Such developments are to be welcomed but their worth needs long

term evaluation particularly as raising the temperature of the disinfectant

increases the volability and may damage the instrument..

In response to the recommendations of the disinfectant manufacturers, the

Medical Devices Agency and those responsible for policy formation in other

countries, the Working Party recommends an increase in the immersion times in

2% glutaraldehyde between patients from 4 to 10 minutes. This change is not

based on new microbiological data and does not mean that patients have been

exposed to unnecessary risk in the 9 years since the 4 minute immersion was

recommended. It is instead a change mainly for political reasons which may

increase the margin of safety while not negating the need for effective cleaning of

the instruments before disinfection. The increased use of automated cleaning

and disinfection machines and the greater number of endoscopes in service

since the previous recommendations were published should enable this change

to be introduced without too much difficulty in most endoscopy units. The 20

minute immersion at the end of the session should continue but the between-

patient contact time of 10 minutes should be adequate at the start of a session

(Table 3)

Table 3

Recommended contact times for Gastrointestinal Endoscopes

Disinfectant contact times (minutes)

2% 0.35% chlorine

glutaraldehyde peracetic acid dioxide

Before a session

Between patients 10 5 5

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