In practice, changes can occur on the surface of medical devices over time due to mechanical, chemical, and/or physical (e.g. thermal) influences. The causes of these surface changes, if they have not already been caused during use, are usually to be found in the treatment process. If surface changes occur, it may be necessary to proceed in a systematic sequence to eliminate and avoid them:
Determine the type, origin and cause
Assess risks
If necessary, implement manufacturer's recommendations for removal
Initiate measures to avoid this, then re-qualify if necessary
The example given about the most frequently occurring surface changes in metallic instruments made of stainless steel (NR steel) and/or products made of plastic or elastomers is based on the above-mentioned system.
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Coatings on metals due to process chemical residues
Depending on the extent of the residues, instrument type, and surface condition, bright to dark gray deposits / discoloration may appear in various sizes. This may become even more apparent following sterilization.
Type of surface changes, origin and causes
Insufficiently removed process chemicals (e.g. caused through spray shadows, incorrect loading) during the intermediate and/or final rinsing are often the cause of the above-mentioned surface changes.
Treatment recommendation
The surface changes can be eliminated by wiping off with a lint-free cloth or by acidic based cleaning with special cleaning agents as recommended by the instrument manufacturer
Preventive Measures
A preventive approach should always be taken to avoid surface changes. For this reason, sufficient intermediate and/or final rinsing with fully demineralized water of the metallic instruments and, if necessary, the loading quantity as well as the loading arrangement should be checked. In addition, manufacturer's instructions regarding disassembly and cleaning must be followed strictly!
Assessment of possible risks
Particularly in the case of ophthalmic instruments, patients could be exposed to risk of chemical burns caused by alkali and surfactant residues.
Want to know more? See Chapter 12 in our latest revision of the AKI red brochure here:
About the author
Aaron Papadopoulos is a member of the AKI since 2018 and is one of the representatives of the process chemical manufacturers in the group. He works within Ecolab Deutschland GmbH in Strategic Marketing for the Healthcare Division taking care of endoscopy and instrument reprocessing.
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