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Influence of glutaraldehyde on the formation of deposits on thermolabile endoscopes.

Glutaraldehyde continues to be widely used in a number of countries for the final disinfection of thermolabile endoscopes.

It has long been described in the literature that this agent reacts by cross-linking with proteins to form large polymer molecules [e.g., Block SS (ed.) Disinfection, Sterilization and Preservation. 5th ed, Philadelphia: Lippincott, Williams & Wilkins, 2001]. On the other hand, glutaraldehyde is a polar substance that can be deposited in nontoxic amounts on surfaces of endoscopes still undergoing final disinfection. These adsorbed amounts can then react with endogenous proteins during the next use of the endoscope on the patient.

The resulting deposits can be easily identified by the discoloration of the marking rings on the insertion part of the endoscopes. This discoloration occurs up to the section where the endoscope is inserted into the patient. Such deposits in channels of endoscopes have also been reported in older publications.

Source: Olympus Europa SE & Co. KG

Of critical importance in preventing the formation of such glutaraldehyde-protein deposits in both manual and mechanical reprocessing procedures for flexible endoscopes is the effectiveness of the rinsing process after final disinfection.

Oxidizing substances, such as peracetic acid, can attack the structure of these deposits and remove them. Thus, when changing the disinfectant for final disinfection from an active substance based on glutaraldehyde to a product based on peracetic acid, it can be observed that after several applications the visible deposits are removed and the marking rings are lightened. In addition, it should be noted that such a change may result in sluggishness in brushing the channels. This is interpreted with the removal of potentially present deposits, for example in the instrumentation channel, which is completed after a few reprocessing cycles.


  • When using glutaraldehyde for final disinfection of thermolabile endoscopes, attention should be paid to indications regarding deposits that may occur, such as discoloration of the marking rings. In this case, the effectiveness of the final rinse process should be checked after the disinfection step.

  • When changing from glutaraldehyde to peracetic acid as the active ingredient for final disinfection, glutaraldehyde-protein complexes are destroyed in the course of several reprocessing cycles and the deposits on the inner and outer surfaces of the endoscopes are removed. Marking rings are whitened and temporary sluggishness may occur when brushing the endoscope channels.

About the Author

PD Dr. Holger Biering studied chemistry at Martin Luther University Halle-Wittenberg, where he also completed his doctorate and habilitation. Until 2010, he worked in various management positions in research and development at Ecolab. Since then he has been working as a consultant for cleaning and disinfection of medical devices for companies and users in the healthcare sector. He is a member of various national guideline and standardization working groups in Germany and the USA as well as international working groups within CEN(Europe) and ISO (worldwide).

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