Unsuspected dilution of glutaraldehyde in an automatic washer for flexible fibreoptic endoscopes.

It has been suggested that serial usage of automatic endoscope washer-disinfectors may result in dilution of glutaraldehyde (used as the disinfectant in these machines). However, there are no published data available to confirm this possibility. The authors therefore undertook a study to determine the extent of glutaraldehyde dilution occurring during repeated cycles of an endoscope washer-disinfector over a 14 day period. It was found that the concentration of glutaraldehyde in the endoscope washer-disinfector consistently fell with increasing numbers of wash cycles, and that after 60 cycles the concentration of glutaraldehyde fell below the recommended minimum effective concentration of 1%. Users of automatic endoscope washer-disinfectors should be aware of the potential for dilution of glutaraldehyde in these machines. It is the number of washer-disinfector cycles, and not only the elapsed time since activation of the glutaraldehyde, which determines the frequency with which the glutaraldehyde solution must be replenished. Test kits are now available to measure glutaraldehyde concentration chemically, and may be useful in a quality control program of serial testing of glutaraldehyde concentrations in the endoscope washer-disinfector.