During surgical procedures instruments are frequently exposed to sodium chloride or ringer solution, which are used for surgical site rinse.

We have to be aware that that physiological sodium chloride contains 4000mg/l – a very high concentration compared to other process steps (blood contains the same concentration). Chloride is the number one root cause of pitting corrosion. Experiments have shown that after a one hour immersion in sodium, severe corrosion is already visible and after a six hour period an instrument is completely destroyed. Therefore, exposure to sodium chloride should be kept as low as possible, especially if corrosion issues already occurred:

• Instruments should be wiped from soil during and after the procedure. An immersion into sodium chloride should not take place.
  
• Ideally no Sodium Chloride is used for cleaning instruments but sterile demineralized water. This is an extra effort for operating room staff (two liquids to be handled) but it is worth it especially in long procedures or if corrosion has already occurred.
• All liquid (Sodium Chloride, skin disinfectants) should be disposed in the OR and the bowls wiped dry. In no case these residual liquids should be spilled over the instruments.
• The time between end of procedure and start of cleaning in CSSD should be kept as short as possible.

In case you are suspicious about corrosion already happening in the OR or would like to establish a new protocol here, we offer support by process optimisation.

The "Red Brochure" recommends a maximum waiting time between end of procedure and start of cleaning of maximum 6 hours

The "Red Brochure" recommends a maximum waiting time between end of procedure and start of cleaning of maximum 6 hours. It has to be noted that in long procedures the time between contamination and cleaning may be longer. However this is not an experimentally proven black-and-white scenario but experience from daily practice. There are a number of influencing factors regarding the effect of an extended waiting time:

• Type of contamination: While pure blood usually dries in maximum 2 hours, mixtures of blood with saline or disinfectants as well as salvia will stay moist for a much longer period of time. Further waiting times on completely dried blood will not have any negative influence but moist contamination may create corrosion over time and the waiting time will increase cleaning issues.
  
• If gross contamination is already wiped from the instrument in the Operating Room, longer waiting times can more likely be tolerated than with disposal in fully contaminated condition.
• Extra efforts in cleaning such as ultrasound, manual pre-cleaning with brushes or steamer can compensate waiting times but of course the corrosion risk may remain increased.
• All of these effects will typically appear gradually. Therefore longer waiting times will typically result in larger numbers of instruments which will be sorted out during visual inspection before packing but not effect 100% of instruments treated as such.

So a waiting period “as short as possible" should be achieved. The individual situation (extra costs, efforts and risks) of viable scenarios should be evaluated and results monitored to achieve the best result for each hospitals situation.

It can be said that efficacy of manual cleaning and disinfection is widely over estimated

It can be said that efficacy of manual cleaning and disinfection is widely over estimated. In the same way dishes do not get clean by soaking them in a sink, instruments only show a very limited cleaning efficacy by soaking. Mechanic action such as brushes and ultrasound have to be applied additionally is especially in instruments with joints. Lumen instruments have to be filled before and flushed afterwards. Steinmann and Rosenberg say that validation/verification is still necessary for the individual ultrasonic bath.

The German societies DFSV (CSSD) and DGKH (hygiene), AKI and VAH (testing of disinfectants) have published a very detailed guideline on proper manual cleaning and disinfection and testing methods. However the human factor will still come into play.

One important guideline is that only a clean product can be thoroughly disinfected. Therefore the "two bath method (one for cleaning, one for disinfection)" has to be used if a combined cleaning and disinfection solution is used. Kamer et al. have researched the properties of various product groups.

Aesculap can support process design by independent testing and process optimisation.

When a standard for demineralized water (EN285 Annex B) was defined for the usage of clean steam generators, ....

When a standard for demineralized water (EN285 Annex B) was defined for the usage of clean steam generators, this water quality was soon taken over as a standard for demineralized water for final rinse, in order not having to maintain two different qualities in a CSSD. The usage of demineralized water is not absolutely necessary for proper cleaning and thermal disinfection and therefore did not become part of DIN EN ISO 15883 but it is an important prerequisite of value preservation of instruments. It is worked out in detail in the "Red Brochure" (10th edition, page 20). In difference to the latest edition of EN285, a conductivity of 15µS is tolerated for final rinse.

However other parameters do not allow much leeway. Tests in our laboratory and practical experience show:

• A chloride level higher than 2mg definitely leads to corrosion due to the high temperature. Tests with 4mg/l and 30min boiling time already demonstrated traces of corrosion
  
• Even a silicate level of 1mg/l (maximum in the standard) may lead to staining; Aesculap recommends a level of maximum 0,4mg/l.

Consulting experience also shows that additives to the final rinse have limited benefits but may cause additional issues:

• Rinse aids are based on tensides. With proper loading the effect on drying of metal instruments is limited. However these rinse aids may lead to stress cracks on plastic material (proper cleaning of containers) and staining.
  
• The same potential negative effects apply to instrument milk. In addition, the desired lubrication effect is not ensured as most likely only some micrograms of oil finds its way into the joints.

Some mathematics illustrate this effect:

• In a typical composition 1ml /l instrument milk, which contains about 10% of oil, so a total of 4g of instrument oil will be present in washer disinfector with 40l of water.
  
• Due to the oil in water emulsification minimum 50% will go to the drain with the water (some people say 90%), which leaves us with 2g.
• Assuming 400 instruments in load we are under 5mg of oil per instrument.
• The oil is evenly spread over the surface. In a regular small clamp the entire surface is about 44cm2, while the joint surface is 2cm2
• This leads to about 0,2mg of oil per joint. A drop of the size of a needle tip for an entire joint of a clamp.

Therefore the red brochure an Aesculap IFUs recommend final rinse with demineralized water without any additives.

Internationally there are various standards how sterile containers should be cleaned and disinfected

General considerations are:

• Containers do not have a direct contact with patients
• If not properly cleaned and disinfected according to their bio-burden they may pose a hygienic risk to people packing
• Necessary prerequisites for sterilization must be given; otherwise there might be a risk of cross-contamination from containers to instruments.

Several routes are used in daily practice:

• Many people say that if a container was removed from the OR before the start of the procedure and was not used for transportation of contaminated instruments, it may be used for next packing without cleaning and disinfection.
  
• For some people this rule is also applied if the container was in the OR but separated from the patient.
• If a manual cleaning and disinfection is used – due to size of container – wiping has proven to be the only suitable method. Alcohol is the most widely used agent, because it is fast action and complete evaporation. If water soluble disinfectants are used (QACs, aldehydes etc.) their residue may cause discolorations or tension cracks on plastic material. It is however unrealistic to achieve a virucidal disinfection by a manual process.
• Machine processes with chemical disinfection are fast but critical in terms of material compatibility. Staining and stress cracks may be the consequences if processes are not carefully adapted.
• Machine processes with thermal disinfection provide the best efficacy. Verification / validation based on individual requirements can be done. Such processes can be installed in regular instrument washers or large chamber container/cart washers.

An individual evaluation of the best sterile container process based on local situation and requirements can be done by the consulting team.

Caused by the machining methods (e.g. grinding, pressing, rolling) and impurities, technical surfaces are not completely smooth

When two technical surfaces move against each other the unevenness can wedge, which leads to abrasion of the surface.[1] Oil between two technical surfaces forms resistant liquid or semisolid films under the influence of pressure and temperature. The oil´s long molecular chains bind to the metal surface comparable with the brushes of a hair brush. This connection allows the two technical surfaces sliding against each other.[2] It is generally recommended to oil the joints of instruments after each cleaning to avoid abrasion and fretting. The project group cleaning determined, that oiling improves the cleaning performance, in studies about reproducible cleaning.[3] S.Norman et.al. tested the effect of care products on sterilization in 2009. Therefore two oil sprays, one with and one without emulsifier, were tested as well as a one bottle oil with emulsifier. Mosquito clamps were cleaned, contaminated with 10μL spore suspension and, depending to the test scenario, oiled and sterilized. Afterwards the clamps were incubated in culture medium for five days and got tested on microbial growth. There were 7 approaches for each oil and one without care products as reference made. No trend was observed in the experiments including gravitation process with 121° C saturated steam. After the fractionated prevacuum cycle with 134° C hot saturated steam hold for one minute 2 of 21 batches with oil were tested positive. With two minutes holding time no, growth has been observed.[4]

Conclusion: The insufficient oiling of joints of surgical instruments leads to adhesive wear. Micro-welding causes wear particles, which damage the surfaces and passive layers and lead to friction corrosion in the end.[5] To prevent early abrasion of the instruments surfaces, oiling of the joints surfaces after cleaning is indispensable. The impacts of oil on the cleaning performance and sterilization parameters are extremely low. The reprocessing cycle is not influenced by maintaining instruments with oil, apart from the expended time.

[1] Fuchs, W., Gaißer, M.: Funktionserhalt chirurgischer Instrumente durch dampfsterilisierbare Öle, 2007, aseptica Heft 2

[2] Von Weingraber, H. , Abou-Aly, M.: Handbuch Technische Oberflächen: Typologie, Messung und Gebrauchsverhalten, 1989, Vieweg Verlag

[3] Kirmse, G.: Untersuchung zur reproduzierbaren Reinigung von Instrumenten anhand eines Worst-Case-Modells, 2011, Zentralsterilisation

[4] Normann, S. , Vollstädt, S. et. al.: Möglicher Einfluss von Pflegemitteln auf die Sterilisation, 2009, aseptica Heft 1

[5] Rieker, C., Medica, S.: 20 mal weniger Abrieb, 98, Sulzer technical review

In general an instrument displaying stains during inspection requires action

The nature of a stain (e.g. distinction between corrosion and organic residue) can not be safely determined just by visual inspection. It also is potential failure of a validated/ verified process so a root cause analysis should be performed, as the most difficult to clean surfaces are not the visible ones.

If a stained instrument is detected an attempt should be made to clean it. This may happen:

1. In the packing area
   
2. By passing back the instrument to the decontamination area

The first solution has the benefit that the set can be completed quickly; but only fully residue free methods can be used, as the set would directly go to sterilization. Lint free cloths with alcohol or instrument oil are widely accepted. Other solutions are hydrogen peroxide (3%) as immersion or steam cleaners, as the only residue left would be water. So called erasers may also remove stains but have to applied carefully in order not to damage the instrument surface (for example available from Aesculap Technical Service by item code TA006938). However there are various judgments of such methods by hygienic officers.

Soaking and the use of brushes and ultrasound are usually the first methods used in the decontamination area. Hydrogen peroxide or aggressive alkaline cleaners can also be applied. These methods would remove all organic residues.

In case this is not successful, we recommend a surface repair by a qualified instrument repair shop, such as the Aesculap Technical Service.

Abrasive cleaning may damage the surface of instruments depending on the composition. While many of such devices are too aggressive, Aesculap made good experience with Chirol Ultra.

All steps applied in post cleaning have to be defined in a work instruction.

It is frequently discussed how far sterile packages can be stacked

While EN868 states how stacking has to be checked, it is left to the respective manufacturer in how far stacking is made as a claim. Conditions have to be made clear. So for each system the individual instructions of use have to be consulted.

Aesculap claims that all Aesculap containers can be stacked up to three containers high. Aesculap containers are designed in a way that such stacks are stable and that steam penetration is still fully possible. However this does not apply for stacking with other brands of containers as their design is not intended to fit to Aesculap containers.

Opposite to this, Kimberly Clarks clearly states that soft packs shall not be stacked due to increased risk of damage.

Eight influencing factors for wet sets

During steam sterilization condensate is produced necessarily (about 300ml per 10kg of instruments), which has to be removed during the drying part of the cycle. The boiling temperature is reduced by vacuum. The drying process either stops if:

• The product temperature in contact with the condensate falls below boiling temperature.
• The atmosphere in the sterilization chamber is saturated with humidity.

Effectiveness depends on various factors:

1. Load of the sterilizer (load condition, total weight, packaging, types of goods)
   
2. Steam quality (overheated or wet steam may lead to poor results)
3. Sterilizer properties (steam distribution, vacuum level)
4. Sterilizer cycle (heating, drying time, fractioned drying)
5. Packaging material (material of container, wraps and try liner influences drying by heat capacity, water adhesion, steam penetration and distribution)
6. Packaging content and weight (overweight sets and plastic trays are frequently difficult to dry)
7. Position in the sterilizer chamber
8. Cool down phase (temperature, heat distribution)

The standard EN285 provides a standardized test, which however does not meet today’s requirements in all aspects. Drying issues are a typical indication of the metrological process analysis in order to find the best way to improve drying results with lowest possible effort.

It has been established that shelf life is not necessarily time related but event related

However it is not clear for daily practice what an event is. Only the German DIN 58953 part 8 gives a recommended shelf life of 6 months.

Additional recommendations for storage are:

• Storage should be in closed compartments or in an accordingly ventilated area
• Controlled temperature and humidity
• Limited access
• Easy to clean surfaces and floors

However the standard points out that environmental conditions and outside contamination are critical factors and the 6 months are only a general hint. Each hospitals hygienic commission has to determine an acceptable shelf life. Frequently a shorter shelf life is used for peel packs.

Aesculap has conducted a successful shelf life study for 12 months with the Aesculap Primeline Container. The used shelf life has to be reasonable based on storage conditions, studies and local test results.

Various procedures exist on how to treat new instruments

Various procedures exist how to treat new instruments such as:

• Washing for several times
• Washing with special programs (degreasing)
• Waiting periods

First and most important reference for such procedures should be the instruction for use of the respective manufacturer as the final treatment of instruments varies.

For new Aesculap instruments the following steps are applied:

• Thorough cleaning with organic and alkaline cleaners
  
• Passivation
• Rinse with demineralized water
• Oiling with "Sterilit I" instrument oil

Therefore Aesculap recommends one regular washing cycle before first packing and sterilization in the instruction for use. Further special treatment is not necessary.

If repetitive washing is performed it is crucial that instruments can cool down completely and have a waiting period between cycles, otherwise corrosion may occur. In general, new instruments are more sensitive to surface changes. Therefore if surface changes have occurred on older instruments, the root cause should be analyzed and the process optimized before larger numbers of new instruments are implemented. Aesculap offers support for this by a "Metrological Process Analysis".

Also, new processes should be checked for potential of staining and corrosion besides the validation /verification for cleaning and disinfection. As this is usually not part of a standard validation/verification it is an important extra step to protect the valuable asset of instruments. The corresponding consulting module is called "Process Verification".