General questions on disinfection and cleaning

Should storage beakers for dressing forceps in doctors’ offices be sterilized on a daily basis, or is sterilization once a week sufficient if the containers are covered sterilely “over night”?

On principle so-called storage beakers have to be considered critical. It is therefore recommended using sterilized dressing forceps (single wrapping).

If this recommendation is not followed, certainly sterilization on a daily basis is safer.

Are there any studies on the use and suitability of pieces of silicone tube to protect the instruments during sterilization (vapor permeability)?

There are no such studies as far as we know. We recommend to always remove the “protection” as soon as the instrument is used / is placed into the sieve.During storage before use the protection should remain on the instrument.

We want to use medical white oil as a lubricant for dental devices. The Medical Devices Directive requires us to provide a clinical assessment or literature proving the conformity and non-objectionability of the white oil used.

It must comply with the relevant applicable pharmacopeia, be physiologically safe in accordance with the German Pharmacopeia and Article 31 Foodstuffs and Commodities Act and must also be permeable to steam/steam sterilizable. It is important to avoid any joints becoming jammed as a result of the cumulative effect or resinification.\"

Additional: Pay attention to the purpose CE marking.

On the issue of washer-disinfectors: Does the performance inspection have to be carried out annually or only every two years as published recently in Dental News (zm)?

You have asked about the interval for the performance inspection on the issue of washer-disinfectors. The Working Group for Dental Instruments (AKDI) at the German Federal Association of Dentists recently recommended that the performance inspection should be repeated after two years provided that the manufacturer of the washer-disinfector specifies no other regulations. The standard EN ISO 15883-1 recommends that the performance inspection is carried out annually and the guideline issued by the German Society for Hospital Hygiene (DGSV), German Society for Sterile Supply (DGSV) and the Working Group for Hospital Engineers (AKI) make the same recommendation. The guideline recommends this interval irrespective of whether the washer-disinfector is operated in a hospital or a dental practice. No account is taken of the fact that the cycle capacity per year and the applications and loading configurations in a dental practice are lower and subject to less variation. The guideline referred to above states that the regular performance inspection should be carried out at the latest six weeks after a service. The manufacturers of washer-disinfectors specify service intervals for dental practices that vary from the intervals defined for washer-disinfectors that are used in hospitals. In the case of the Miele dental washer-disinfector, for example this interval is 1000 operating hours or 1.5 years and practitioners would be fully justified in linking the intervals for the performance inspection to this service period. Given that there are certain tolerances (these periods are ultimately only recommendations) and including the limit of six weeks, we therefore arrive at an interval of 1.5 to 2 years, provided that the process is sufficiently robust over this period of time.

However, we are living in a federal country and the supervisory authorities in different states are apt to perceive this issue in different ways and they may well be rigid in applying the annual interval. You therefore need to be aware of the acceptable interval in your region in the event of an inspection.

Our nurses reported that changes (corrosion) occurred on the surgical instruments since we started to use Lavanid solutions. Are there any studies on this subject?

Lavanid solutions on the basis of Ringer solution contain 0.9% chlorides. The main ingredient being sodium chloride, they also contain small amounts of calcium chloride and potassium chloride. Your nurses’ observations of corrosion on the instruments since you started using Lavanid solutions are therefore comprehensible.

We recommend a test to find out how to minimize the effect of solutions containing chloride - or even worse the drying of solutions containing chloride, such as Lavanid solutions, -on instrument steel.

What is the maximum weight for a sterilizing unit?

Indications of the weight for a sterilizing unit are found in prEN 868 and DIN 58953: prEN 868-8, item 4.28: Loading: A sterilization container of standard size, i.e. the size of a sterilization unit, must be made and designed in such a way that a load with a total weight of up to 10 kg can be sterilized in a sterilizer. Fractions of that size must be able to receive proportionately smaller loads.

DIN 58953-9, item 5.1: Instruments are sterilized on perforated sterilization trays in the sterilization container, in conformity with DIN 58952 Part 3.

Note: Ergonomic requirements mean that the loading weight of a sterilization container should not exceed 10 kg. This also avoids high volumes of condensate. Always follow the sterilizer manufacturer's instructions on loading.

What is important to know when machine processing OT shoes? Is it necessary to run a cycle without batch, if medical devices are to be processed after having run a sterilization cycle with shoes in order to remove plastics residues out of the chamber?

Your question has often been discussed with experts in the recent years. Seen from a microbiological point of view, it is no problem to process medical devices and OT shoes alternatingly. However, during the processing of OT shoes, particles and fluff from socks tend to deposit in the trays and baskets of washer disinfectors. Such deposits could slip through and washed into medical devices with small lumen. This risk exists particularly in the case of MIS and ophthalmologic instruments. A cycle run without batch does not eliminate this problem. When sterilizing medical devices after processing OT shoes it is important to know, whether it is possible to clean the trays and baskets sufficiently and to remove any deposits and fibres. Only if such a cleaning is assured, you should use your processing machines with such changing types of loads. If not, we recommend to process OT shoes in washer disinfectors which are explicitly provided for them.

Is it possible and acceptable to clean and sterilize MIS-instruments without prior disassembly?

As a principle rule, instructions for processing and / or the manufacturer must indicate a method of processing. Instruments must be disassembled according to the instruction of the manufacturer.

Which disinfecting cleaning agnets can be used for the cleaning (prior to disinfection) of semi-critical and critical instruments belonging to group A (manual application in ophtalmologist surgery)?

Use cleaning agents that are not protein fixing when cleaning semi-critical and critical instruments of group A manually prior to disinfection. These cleaning agents must meet the requirements of a medical device class 1 (cleaning agent) or class 2a (disinfectant). The cleaning agent used may be with or without anti-microbial effect. If a product without anti-microbial effect is used, the protection of the personnel must be ensured by appropriate measures (protective clothing). In general, any kind of cleaing agent, combined cleaning and disinfecting agent cleaning agent with disinfecting effect can be used, provided it is recommended by the manufacturer for this use and it is a medical device. It is important, however, to make sure, that products are used, whose ingredients doesn't cause any protein fixation which would impede the following cleaning or disinfection. Such ingredients would be anti-microbial agents belonging to the group of aldehydes and alcohols. That is why the use of disinfectants containing aldehydes or alcohol is not recommended for this application.
When using cleaning agents with disinfecting effect make sure that at least a bactericidal and limited virucidal effect exists within the application conditions. This is a protective mesure for the personnel which is most important in this case.

In general, follow the manufacturer's instructions concerning concentration, temperature and residence time when using cleaning agents and disinfectants. AKI recommends to use solutions that are daily prepared or renewed more often in case of heavy soiling. When cleaning or disinfecting make sure that all outer and inner surfaces have contact with the agent, particularly of instruments with narrow lumen, such as tubes and cannulas, or with hollow spaces and that they are free from obstructions.

After the treatment with a cleaning agent, the instrument must be sufficiently rinsed by clear running water, in order to prevent the carry-over of cleaning agent deposits to the following disinfection bath. Rinsing also removes any remaining soil.

How can an instrument cleaning and disinfection machine be validated if there is no batch documentation in the form of a measuring strip (temperature/time measurement)?

Testing and furnishing documented proof (validating) that the cleaning and disinfection procedure meets the required specifications is carried out during the setup procedure and then at regular intervals subsequently. This is achieved in conformity with prEN ISO 15883-by checking the temperature in the washer compartment of the items to be rinsed. Sensors connected to a measuring unit are integrated in the walls and inserts. These sensors are independent of the control system for the automatic machine. Cleaning performance must also be checked and in this context we refer you to the "Stellungnahme des AKI zur Prüfung von RDT-Automaten mit Reinigungsindikatoren" ( AKI bulletin on testing automatic washers/disinfectors (W/D) with cleaning indicators). Current standard practice often involves the use of data loggers for frequent, independent temperature checking. However, bioindicators, are still used to check the overall effect of germ reduction by cleaning and disinfection. The process or batch data is usually documented as a plot of temperature against time based on the data obtained from sensors connected to the control of the W/D. This data only relates to a reference point on the bottom plate of the washer compartment. Documentation between each validation provides concrete evidence that the validated procedure is precisely reproduced. It also indicates and that the instruments in the batch have been reprocessed using a validated procedure.

Does thermal disinfection require 93°C / 10 min or would 90°C / 5 min be sufficient - where is this documented?

The international standard for cleaning and disinfection devices prEN ISO 15883 has introduced the term Ao to define the disinfection effect of a procedure. Ao is the time in seconds at 80°C required to kill or deactivate a specific group of microorgansims at a z-value of 10. Temperatures and exposure times relate to points between the items to be sterilized and the walls of the device. They do not relate to measuring points outside the washer compartment. Ao = 600 corresponds to 10 min at 80°C and this is sufficient to kill any vegetative form of bacteria, fungal spores and thermally unstable viruses. An Ao of 3000 is required to deactivate Hepatitis B viruses and this corresponds to 5 min at 90°C or 50 min at 80°C.
The Robert-Koch institute suggests an Ao value of 3000 for the disinfection stage of reprocessing surgical instruments (compare Central Sterilzation 1999; 7th edition, pages 81-82).

Is it possible to leave instruments unprocessed overnight or over the weekend? Is wet disposal by immersion over night or over the weekend a possible alternative?

Practical experience has shown, that soiled instruments can be left untreated up to 6 hours after their application without affecting the cleaning in the machine. If the instruments are stored over night or over the weekend, sufficient cleaning cannot be assured. In addition there is the risk of corrosion due to blood that adheres over a long period or due to a physiological salt solution. If soiled instruments are stored over night or over the weekend you must expect corrosion.

Is the forthcoming pren 15883 document an international standard or a European standard?

The forthcoming pren 15883 is an international standard. The parts 15883 - 1 and 15883 - 3 will be published by the beginning of next year (in spring time). The part 15883 - 2 has also already been agreed upon and will be issued by the end of next year.

What is the difference in the efficacy of instrument oil or instrument spray (paraffin spray) and when should these be used?

Depending on the situation either oil from a spay can or from a drip can may be adequate. In both cases the oil quality in the cans should be identical with regard to the lubrication effect and steam steralizability. It is important to apply the oil in a targeted manner. The rule to be applied is: as much as necessary but as little as possible! Caution: Pure white oil / paraffin oil or instrument oil (which are different names for the same quality) is not suitable for steam steralization because it does not contain any emulsifying additive.

In the manufacturer's instructions for a medical product (MP) specifies sterilization with ethylen oxide as the sterilization procedure. May I sterilize this MP with formaldehyde because EO is not available?

The individual steps of the EO and the FA procedures are completely different. Whether the MP can be sterilized using FA may either be assessed by the manufacturer or can be shown in a risk analysis. The latter, however is often impossible. We therefore recommend contacting the customer and requesting a written approval/certification.

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