Staining/residues on medical instruments are not always caused by lack of hygiene
The closure of several Central Sterilization Service Departments (CSSDs) in Hessian hospitals has attracted a lot of attention in the last few weeks. There have been reports of deficient hygiene in instrument reprocessing and thus the impression has been given that grave hygienic deficits exist for medical devices in German hospitals. The scenarios described by the press however, have not in our opinion all been correctly evaluated and therefore prematurely categorized as a hygiene risk due to inadequate cleaning.
In one of the affected hospitals experts could not confirm inadequate hygiene for instruments even using test. Neither did CSSD or operating staff consider cleaning results of reprocessing inadequate at any time.
It turned out later that the stains on some instruments were silicate deposits, which definitely do not indicate a problem for hygiene due to inadequate reprocessing.
The formation of these deposits was probably due to inadequate steam quality in the sterilization process. Formation of deposits or stains on instrument surfaces can happen in any good medical device reprocessing procedure-but in our opinion this does not justify shutting down the CSSD concerned. These residues do not generally constitute a hygienic or toxicological risk for patients. We are talking here about a cosmetic change and not a deficit in reprocessing quality.
It is very alarming that such a decision has been reached even so, because it not only damages the reputation of the department, but also that of hospital and therefor its economic success. Generally it is a good thing that external experts are brought in such cases, to support the supervisory authorities with relevant know-how from a special area. But it must be ensured that mandated measures are not subject to economic interests.
Therefore, independently of economic interests, a professional, realistic evaluation of the situation on the ground and its swiftest optimization should be paramount. Because of the prevailing public pressure on hospital and those carrying responsibility at such times, the measures recommended are understandably rarely questioned by those affected. It is far more likely that the often very expensive and partly unnecessary measures are implemented without further examination of the facts.
The expert group from the Working Group Instrument Reprocessing (AKI) has already given its reaction to the current situation with a public statement on these at least partially exaggerated measures, to try to prevent further over reaction and possibly unjustified department closures.
In many central sterilization service departments the appearance of stains is known to occur from time to time. Which are the most common types of deposits or surface discolorations appearing inthe CSSD? How can their risk potential be assessed and which suitable remediescan help?
The following is a summary of some types of stains, those that from the point of view of users appear in the CSSD most frequently. These are gathered from individual’s experience from various sterile service departments.
硅酸盐沉积变色 Silicate deposits
Experience shows that the phenomenon of silicate deposits has occurred at least once in the history of any central sterilization departments. It occurs repeatedly in some hospital and can never be entirely ruled out.
As described in depth in the "Red Brochure" (AKI) this type of deposit is a yellow-brown to blue-purple stain on instrument, in the chambers of washer-dis-infector(WD) and also sterilisers.
It can arise due to the occurrence of silicic acid slippage during production of fully demineralized water (FD water). The culprit can be the ion exchangers and the reverse osmosis water treatment plant, which when the exchange cartridge is exhausted allows silicon oxide from the feed water into the reprocessing circulation. This silicic acid slippage can even be present when the microsiemens value (uS/cm) of the fully demineralized water lies below there commended level.
Silicate deposits can also from on surfaces when minerals are present in the process water and in the final rinse water orvary carrying – over of detergent containing silicates in the final rinse of the WD. But in most case the cause is in some way connected to the fully demineralized water quality.
Of course the cosmetic effect is quiteshocking the first time you see it- but current scientific knowledge shows that there is no hygienic risk for patients or for the environment. It is simply acosmetic effect, which actually provides a certain protection (passive layer)for the medical device concerned.
找出硅酸盐沉积的原因，最重要的是首先查看纯水的处理并与相关技术人员进行探讨。例如离子交换器是否进行过更换或更新及最近一次更换或更新是什么时候？制取纯水的处理过程是否发生变化？最近一次的水或蒸汽的质量检查何时进行？这也是经常会建议相关实验室对水质进行常规监测的原因。 (蒸汽灭菌时水质符合EN 285标准（附录B－表B1）或DIN 58946标准第6部分)。
To find out of the cause of the silicate deposits, it is important first of all to look at fully demineralized water treatment and discuss with the technicians involved. For example whether and when the ion exchanger was last changed or renewed, whether there have been process changesin the treatment of fully demineralized water, and even when the quality of the water or steam was last checked. This is why it is also always advisable to have regular water monitoring conducted by the relevant laboratories (See Water Quality for Steam Sterilisation according to EN 285, App. B, Table B1 or DIN58946 Part 6）.
In addition it is necessary to check whether the dosage applicance is correctly connected to the WD, whether neutralization and intermediate rinse occurs adequately as intended. Here WD and chemical manufacturers can support each other. In hospitals with less than modern water pipes have been installed. This sort of pipe work can also cause discolouration on instruments, WDs and sterilizers.
In order to work out more exactly where the deposits are coming from in the reprocessing procedure, it is to be recommended, for a defined period of time, to sterilize one instrument in the sterilizer again and again or to fix one instrument into the WD and to washand disinfect it repeatedly. Thus a distinction can be made between causes of deposits can be from these two processes. When the causes have been found and remedied, basic cleaning of the medical devices including appliance chambers should be carried out.
水垢、氧化变色 Lime scale, oxidation
Sporting from water droplets caused lime scale and discolouration of surfaces by oxidation are commonly seen on instruments and are one of alterations that are purely cosmetic. Lime scale residues (chalk) often form where the calcium and the magnesium ion content of the process water used for cleaning or in the final rinse is too high. Using fully demineralized water in the final rinse of the WD can prevent these milky chalk residues.
Discoloration of the surfaces caused by oxidation shows as a grey-black stain. These stains are related tothe material composition of the stainless steel instruments, the proportion of chrome to carbon. The higher the carbon content of the material, the faster agrey-black appears.
钛及阳极氧化铝变色 Alterations to material likeTitanium and anodized aluminium
It is almost impossible to avoid the discoloration of titanium materials in the central sterilization service department. The factors necessary for reprocessing-temperature, moist heat and process chemicals-react with the material surface and colorful,iridescent oxide layers form, which are however definitely hygienically speaking harmless and toxic.
Anodised aluminum is similarly difficult. Eloxal reacts sensitively to both alkalinity and acidity. Here, eventhe rising pH value (dependent on temperature and time) of softened water cancause changes to Eloxal surfaces, which appear as a white, floury residue on surfaces.
After several sterilization cycles Eloxal surfaces become more durable to external influences. It is however recommended when reprocessing Eloxal and colored Eloxal to optimize theinterplay between all the process parameters such as water quality, dosage and sufficient number of rinses to prevent carry-over of alkalinity.
弯盘的变色 Residues on OT dishes
In central sterilization departments one often notices discoloration of OT dishes. Here the exterior ofthe dish is suitably shiny, but on the interior here is a blue/purpleiridescent, sometimes greyish residue. The reason for this is that the dishesare heated over lengthy sessions in the operating theatre, which sodium chloride solution, swabs etc. are in them. Heating causes the salts in the fluids to crystallise out, causing encrustations discoloring the utensil. The alterations in color are generally caused by an oxidative reaction and aretherefore not a problem for hygiene or toxicology.