General questions on disinfection and cleaning

Should storage beakers for dressing forceps in doctors’ surgeries be sterilised on a daily basis, or is sterilisation once a week sufficient if the containers are under a sterile cover overnight?

In principle, storage beakers have to be considered critical. It is therefore recommended using sterilised 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 silicone tubing to protect instruments during sterilisation (steam 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 mesh tray. 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 Device Directive requires us to provide a clinical assessment or literature proving 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 sterilisable. It is important to avoid any joints becoming jammed as a result of the cumulative effect or the build-up of resins.\" Additional: Pay attention to CE marking.

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

You asked about the interval between performance inspections on washer-disinfectors. The Working Group for Dental Instruments (AKDI) at the German Federal Association of Dentists recently recommended that performance inspections should be repeated every two years, provided that the manufacturer of the washer-disinfector does not specify otherwise. The EN ISO 15883-1 standard recommends that a performance inspection is carried out annually and the guidelines 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 guidelines recommend 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 less demanding 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 service work. 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 Miele dental washer-disinfectors, 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, Germany is a federal state and the supervisory authorities in different states are apt to perceive this issue in different ways and they may well insist on an 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 surgical instruments since they 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. Nurses’ observations of corrosion on the instruments since they started using Lavanid solutions are therefore understandable. We recommend a test to find out how to minimize the effect of solutions containing chloride - or even worse, dried-on solutions containing chloride, such as Lavanid solutions, on instrument steel.

What is the maximum weight for a sterile supply unit?

Indications of the weight of a sterilisatopm unit are found in prEN 868 and DIN 58953: prEN 868-8, item 4.28: Loading: A sterilisation 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 processed in a steriliser. Fractions of that size must be able to receive proportionately smaller loads. DIN 58953-9, item 5.1: Instruments are sterilised on perforated trays in the container in conformity with DIN 58952 Part 3. Note: Ergonomic requirements mean that the loading weight of a sterilisation container should not exceed 10 kg. This also avoids high volumes of condensate. Always follow the steriliser manufacturer's instructions on loading.

What is important to know when reprocessing theatre shoes in a machine-based system? Is it necessary to run a cycle without a load if medical devices are to be processed after having run a sterilisation cycle with shoes in order to remove plastic residues from the chamber?

Your question has often been discussed with experts over recent years. Seen from a microbiological point of view, it is no problem to process medical devices and theatre shoes in alternating cycles. However, during the reprocessing of theatre shoes, particles and lint from socks tend to deposit in the trays and baskets of washer disinfectors. Such deposits could enter and become lodged in narrow-lumened medical devices. This risk exists particularly in the case of MIS and ophthalmic instruments. A cycle run without a load does not eliminate this problem. When sterilising medical devices after reprocessing theatre 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 can use your washer-disinfector ???? with a variety of different loads. If not, we recommend reprocessing theatre shoes in washer disinfectors set aside for this particular purpose.

Is it possible and acceptable to wash, disinfect and sterilise MIS instruments without prior disassembly?

In principle, instructions for processing and / or the manufacturer must indicate a method of reprocessing. Instruments must be disassembled according to manufacturers' instructions.

Which disinfecting detergents can be used for washing (prior to disinfection) of semi-critical and critical instruments belonging to group A (manual use in ophthalmic surgery)?

Use detergents which do not denature proteins when cleaning semi-critical and critical Group A instruments prior to disinfection. These detergents must meet the requirements of a medical device class 1 (detergent) or class 2a (disinfectant). The detergent 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 through appropriate measures (protective clothing). In general, any kind of detergent, disinfecting detergent or disinfectant can be used, provided it is recommended by the manufacturer for the purpose in hand and it is classed as a medical device. It is important, however, to make sure that products are used, the ingredients of which do not cause protein denaturation which would impair subsequent washing or disinfection. Such ingredients would include 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 disinfecting detergents, make sure that at least a bactericidal and limited virucidal effect applies under the specific conditions of the application. This is an important protective measure aimed at protecting personnel. In general, follow the manufacturer's instructions regarding concentration, temperature and exposure time when using detergents and disinfectants. AKI recommends the use of solutions that are daily prepared or renewed more often in the case of heavy soiling. When washing or disinfecting, make sure that all outer and inner surfaces have contact with the agent, particularly in the case of instruments with narrow lumens, such as tubes and cannulae, or with hollow spaces, and that they are free from obstructions. After reprocessing with detergent, the instrument must be sufficiently rinsed in clean running water in order to prevent any carryover of detergent to the following stage. Rinsing also removes any remaining soil.

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

The international standard covering washer-disinfectors, prEN ISO 1588,3 has introduced the term A0 to define the disinfection effect of a process. A0 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 sterilised and the walls of the device. They do not relate to measuring points outside the chamber. A0 = 600 corresponds to 10 mins. at 80°C and this is sufficient to kill any vegetative form of bacteria, fungal spores and thermally unstable viruses. An A0 value of 3000 is required to deactivate Hepatitis B viruses, corresponding to 5 mins. at 90°C or 50 mins. at 80°C. The Robert Koch Institute suggests an A0 value of 3000 for the disinfection stage of reprocessing surgical instruments (compare Central Sterilisation 1999; 7th edition, Pages 81-82).

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

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

Is the forthcoming prEN 15883 an international standard or a European standard?

The forthcoming prEN 15883 is an international standard. Parts 15883 - 1 and 15883 - 3 will be published by the spring of next year. 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 oiler may be adequate. In both cases the oil quality should be identical with regard to the lubrication effect and steam steralisation. It is important to apply the oil in a targeted manner. The rule 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 steralisation because it does not contain any emulsifying additive.

Manufacturers' instructions for a medical product (MP) specify sterilisation with ethylene oxide. May I sterilise this medical product with formaldehyde if EO is not available?

The individual stages of the EO and the formaldehyde processes are completely different. Whether a medical product can be sterilised using formaldehyde is determined either by the manufacturer or can be proven in a risk analysis. The latter, however is often impossible. We therefore recommend contacting the customer and requesting a written approval/certification.

Is it true that in future a thermal disinfector will be required to reprocess instruments?

Question: We are currently setting up a new gynaecological practice without an operating theatre. Our medical products are at most semi-critical, e.g. spiral instruments. We have a group B steriliser. So far we have placed the instruments in a cleaning and disinfecting solution and cleaned them in a commercial dishwasher after the day's consultations and then sterilised them. Spiral items were shrink-wrapped and sterilised. Is it true that in the future you will need a thermal disinfector to clean the instruments? In order to do so, would they have to be kept dry until they are machine-cleaned? Am I understanding this correctly? Will the instruments also have to be sterilised? We are based in Baden Württemberg. What are the advantages of mechanical cleaning compared to the previously mentioned methods? Answer: In principle, cleaning and disinfection procedures for instruments must be clearly described (work instructions) and demonstrably produce the requisite results. Procedures must be validated according to the Operator Ordinance. From the point of view of the guidelines body of the DGKH, DGSV and AKI associations for the reprocessing of medical devices, this is possible both manually and mechanically. In comparison to the validation of a machine process, it is not easy to prove the success of a manual procedure and therefore preference should be given to machine-based processes. Mechanical reprocessing is carried out in washer-disinfectors (WDs), which are also medical devices and must comply with the requirements of the EN ISO 15883 standard. The procedures in RDGs complying with this standard can be validated, whereby disinfection is preferably carried out thermally in accordance with relevant recommendations. Reprocessing or only cleaning in a household dishwasher cannot be validated and is therefore not permitted. So far, manual procedures have not really been validated. Therefore, the above-mentioned guideline group is currently developing practice-oriented recommendations for implementation, whereby the performance criteria and level of proof must not differ from those of machine reprocessing. However, the effort involved is considerable, so that mechanical cleaning and disinfection is the simpler and safest method. When using a washer-disinfector, the instruments are loaded directly into the unit from the treatment room in the case of 'dry' disposal and collected for up to six hours,by which time at the latest the programme is started. After thermal disinfection at the end of the process at 90°C for 5 minutes exposure time and drying, specula can be used again. According to the RKI guideline (2001), sterilisation is optional for these specula.

In our washer-disinfector, detergent was found in the final rinse during validation resulting in excessively high conductivity. What can we do to prevent this in the future?

During validation, it was determined that the conductivity in the final rinse water 1is too high. It is unhelpful if the validating technician has simply left you with this negative result, without any further information. At the very least, he could have made some assumptions or ruled out the possibility that this was due to the carryover of wash water by items that retain water. That would be an easy cause to assess. If the processes in your machine rely on an alkaline, mineral-based detergent, then neutralisation with a citric acid-based agent should definitely be added to the final rinse to facilitate removal of detergent residue. Furthermore, you should check whether the rinse water is pumped out completely at the end of each rinse cycle. If this is not the case, the drainage system must be subjected to technical examination. In any case, rinsing can be significantly improved by programming an additional intermediate rinse step. These points should be clarified.

Is it mandatory to complete the sterilisation assistant's technical training course Part I to ensure proper (professional) reprocessing of Class A instruments?

The project group RKI-BfArM-Recommendation has issued a guideline for the monitoring of reprocessing. There you will find an answer to your question on Page 10, which reads as follows "Qualification of personnel in accordance with § 4 Para. 3 MPBetreibV: for personnel without relevant vocational training: expertise through qualification based on the content and scope of the DGSV's course Specialist knowledge I for personnel with proof of relevant training: expertise depending on practical activity and MP spectrum B). Semi-critical B: technical expertise (e.g. endoscopy) Critical B: CSSD: expertise according to management: expertise III, if necessary expertise II Shift management: expertise II Staff: at least expertise I of the DGSV Specialist medical practices: expertise with limited MP spectrum Critical C: Expert quality manager, expertise according to management and deputy: Expertise III Shift management: Expertise II Employees unclean area: Expertise I and II Employees packing zone: Expertise II of the DGSV".

Can an aluminium tray be washed in a thermal disinfector?

In principle, aluminium trays can also be machine-washed. However, please note that both natural and colour anodised layers can be degraded by unsuitable cleaning agents, but also by unsuitable water qualities. This damage is noticeable by a fading or partial loss of colour in coloured anodised aluminium trays as well as by the formation of a powder-like surface coating consisting of aluminium oxide due to the dissolution of the anodised layer. This results in a significant reduction in abrasion resistance. Ideal, for the machine-based reprocessing is a pH-neutral or at best mildly alkaline detergent at main wash temperatures of between 40 and 50 °C as well as the use of fully demineralised water in the final rinse, which in modern programme sequences is also the thermal disinfection cycle. Other water qualities, in particular softened water, can severely damage the anodised layer at the high temperatures which prevail during thermal disinfection due to a significant increase in alkalinity. Please also see our explanations in the grey AKI brochure.

Does an instrument legally have to be accompanied by instructions for use or reprocessing?

There are different requirements depending on country-specific laws / regulations, this also depends on the instrument and the (risk) classification in the respective country. In the EU, according to the Medical Device Directive Annex I (13.1), instructions for use for Class I and IIa products can be dispensed with if the product can be used completely safely even without instructions for use, i.e. the product "does not require explanation".

Surgical instruments with joints, etc. are lubricated before steam sterilization A. What are the health hazard requirements for such lubricants? B. Can you name products that meet these requirements?

Composition: Paraffin oil according to DAB9 and FDA Regulations 21 FR178.3620 (b) = (a) + emulsifier. (All additives must be approved according to §31 Abs. 1 LMBG and be physiologically harmless). 2. The instrument oils of all medical device manufacturers who have classified their instrument milk as a medical device meet these requirements.

Are there any studies on the use of lubricants/instrument milk and their permeability to steam?

An essential statement applies to substances with which instruments are lubricated: They must be permeable to steam so that the vapour reaches the instrument parts lying under the instrument milk. The ability to sterilise in steam must be indicated on the care product. Oils that do not have an emulsifier added are not steam-sterilisable, for example.

We are always looking for suitable lubricants and instrument milk. Unfortunately, we have not yet been able to find a product with all the requisite approvals.

As a rule, lubricants/instrument milk are sold as medical products with CE marking. When used for its intended purpose, this ensures that the product poses no danger to the patient or user or to third parties. The safety datasheet certifies that no particular risks to humans or the environment are known. Skin irritations, as described in the safety datasheet, can - but need not - occur. Suitable preventive measures, such as the wearing of protective gloves, prevent possible problems.

In your treatment advice to remove various types of stains, you recommend an acidic detergent. Please state what is meant by this.

To remove certain inorganic stains from stainless steel instruments, acidic products are recommended which are specially manufactured and declared for this purpose. These products are based either on phosphoric acid or inhibited hydrofluoric acid. Phosphoric acid-based products are suitable for removing limescale and rust and other deposits soluble in acids from stainless steel instruments, for example. The use of products based on inhibited hydrofluoric acid is recommended for silicic acid or silicate deposits because these are hardly removable with conventional acids. In any case, it is advisable to follow the manufacturer's instructions. Neodisher® IR (based on phosphoric acid) and neodisher® IS (inhibited hydrofluoric acid) from Dr. Weigert can be used. Ecolab's Secumatic® FNP (based on phosphoric acid) is also an option.

Are there any findings on the behaviour of instruments made of lead (e.g. lead hand) during washing and sterilisation. Can residues or deposits lead to complications in wound healing?

According to the present state of knowledge and test results, reprocessing under the conditions recommended by the manufacturer is not critical with regard to the topic of deposition / residues from lead hands. The values determined in the final rinse on a trial basis are well below the limit values specified by the Drinking Water Ordinance.

Since when and why exactly are cotton cloths to be sterilized on mesh trays or why should they no longer be used quite generally? Please indicate the DIN ISO standard, if available.

Objections to cotton cloths come from two different directions. On the one hand, a standard has been developed which defines requirements for surgical clothing/surgical textiles with regard to the material: DIN EN 13795-1, edition: 2003-02, Surgical drapes, gowns and clean-air clothing for use as medical devices, for patients, clinical staff and equipment - Part 1: General requirements for manufacturers, processors and products; German version EN 13795-1:2002, Part 2 (draft) test procedures. Due to these requirements, e.g. protection against soaking, it was concluded (even before the existing test procedure standard) that some previously common materials do not meet these requirements. Although packaging materials were explicitly excluded from this standard, this discussion was also applied to inner packaging/sterilised goods by various parties and, in particular, cotton textiles became the subject of discussion. In my opinion, however, no 'ban' on the use of cotton cloths as inner packaging can be derived from this standard. The second aspect of the relevant discussions comes from the requirement to validate the reprocessing. In the evaluation/assessment of processes, increasing attention is being paid to ensuring that the inner packaging of sterilised items (e.g. instruments) is lint-free. This is naturally not the case with cotton textiles. An evaluation of the requirement for lint-free sterilisation cannot be made at this point.

How should non-sterile implants (plates, screws) be prepared before use on patients?

We recommend treating the products according to the hospital's guidelines for reprocessing products that are used sterilely on patients. The manufacturer information must be integrated into these guidelines. We are not aware of any special normative or regulatory regulations for implants.

What is the minimum time required for the rinse cycle in the case of manual reprocessing and how can it be proven that rinsing was successful or, if necessary, that residues are chemically detected?

Analytical methods detect certain key substances contained in process chemicals in order to draw conclusions about the concentration of the actual process chemical in wash water. In principle, this is also possible for manual processes. However, the analytical methods to be applied are different for each process chemical and cannot be used in routine instrument reprocessing. A simple option in routine operation is when alkaline cleaning agents or acidic neutralising agents are used. In this case, pH strips can be used to check for alkaline or acidic reactions in water droplets or residual moisture still adhering to medical devices after the end of the programme. Detailed residue analysis methods can be obtained from manufacturers of process chemicals or detergents and disinfectants for manual use.

Are there also Semi-critical A medical products?

Semi-critical A medical products are ones which come into contact with mucous membrane or pathologically altered skin where levels of cleanliness can be checked by visual inspection. Examples are specula, impression plates or mouth mirrors (cf. RKI guideline Nov. 2001).

Which standard obliges manufacturers of process chemicals to ensure that instruments are rinsed sufficiently during mechanical reprocessing so that no residues of disinfectants or cleaning agents remain on their surfaces?

The prEN ISO 15883 "Washer Disinfectors" stipulates that a manufacturer of process chemicals for automated instrument reprocessing must specify a maximum permissible level of process chemicals in the rinse water or on the reprocessed medical devices that does not pose a risk to patients. In addition, the process chemical manufacturer must be able to specify appropriate analytical methods capable of detecting even lower concentrations than those declared safe for patients.

Which conditions must be met regarding the reprocessing of instruments from the Critical C group?

The requirements for reprocessing Critical C instruments are defined in the recommendation of the Commission for Hospital Hygiene and Infection Prevention at the Robert Koch Institute (RKI) and the Federal Institute for Drugs and Medical Devices (BfArM) in "Requirements for hygiene in the reprocessing of medical devices". A copy of the publication in the Federal Law Gazette is attached. Page 6 provides the corresponding requirements under Point 1.4. According to this, certification of the QM system by an accredited body must be available.

How can a washer-disinfector be validated if there is no batch documentation in the form of temperature/time readings?

Testing and documented proof (validation) that a cleaning and disinfection process meets the required specifications is carried out during the setup procedure and thereafter at regular intervals. This is achieved in conformity with prEN ISO 15883-by checking the temperature of the load in the machine chamber. Sensors connected to a measuring unit are integrated in the walls and inserts. These sensors are independent of machine's control system (redundant controls). Cleaning performance must also be checked and in this context we refer you to the 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 reduction in the titre count through washing and disinfection. The process or batch data is usually documented as a plotted temperature/time chart using the data obtained from sensors connected to the washer-disinfector controls. This data only relates to a reference point on the base of the chamber. Documentation between each validation dates provides concrete evidence that the validated procedure is precisely reproduced. It also indicates and that the instruments in the load have been reprocessed using a validated process.

Where can I find the final report of the Task Force (RKI) on vCJD?

Variant Creutzfeldt-Jakob Disease (vCJD): epidemiology, detection, diagnosis and prevention with special emphasis on minimising the risk of iatrogenic transmission through medical devices, in particular surgical instruments. The final report of the vCJD Task Force can be downloaded (PDF file, 195 KB) from:

Can medical devices be pre-treated with H2O2 in view of the RKI recommendations of the Task Force on vCJD?

The recommendations of the Task Force on vCJD at the RKI provide for a pre-cleaning that does not denature proteins. Aldehydes and alcohol are mentioned as examples of protein-fixing agents. Hydrogen peroxide, on the other hand, does not denature proteins and can therefore be used for pre-cleaning purposes.

Do instruments made of stainless steel lose their useful properties through reprocessing?

Established cleaning, disinfection and sterilisation processes neither in individual applications nor cumulatively influence the original hardness, strength, toughness, cutting and wear properties of thermostable medical devices. Consequently, the prefractioned steam sterilisation process, which is often discussed without justification in this context, should be preferred as it is most effective from a hygienic point of view.

Does certification have to be available when reprocessing as a service for external customers?

Certification is not generally required for the reprocessing of surgical instruments for external customers if it can be guaranteed that the customers receive their own instruments back. § 3 MPG, Point 11 defines 'bringing into circulation' and excludes the following: "A supply arrangement does not exist if medical devices are reprocessed on behalf of a third party and returned to that party after reprocessing. Since this activity does not constitute 'bringing into circulation', it is not necessary to carry out CE marking according to § 6 MPG. Consequently, there is also no requirement for a conformity assessment process and certified QM systems. This legal situation already applied before 01.01.2007. However, in most cases of reprocessing on behalf of third parties, a QM system has been introduced and certified. Customers often require this in order to have confirmation from an independent body that the contracted party reprocesses in conformity with standards and in a hygienic manner. Often the third-party instrument reprocessing companies also decide to obtain certification independently in order to protect themselves against product liability issues. Irrespective of this, it must be noted that certification is required for the reprocessing of Critical C items.