Proper maintenance of instruments

Instruments represent a significant material asset within the overall investment of a hospital. The practical experience mentioned here is combined with a description of fundamental relationships and is intended to help preserve the functional capability and value of the instruments over many years through correct care and maintenance. The recommended measures must be implemented in compliance with hygiene requirements.

Introduction[edit | edit source]

This article includes instructions for the preparation of elastic rubber and plastic instruments as well as for the surgical motor line. Detailed instructions are given for the proper preparation of instruments.

Detailed information is given regarding steel materials for instruments, the required quality of water and further recommendations for the proper handling of instruments.

The requirements for the various types of steel are based on national and international standards (DIN and ISO) with special consideration of the specific functional characteristics and demands for the use of surgical instruments.

When inquiring about the meaning of terms like "high-grade steel" or "stainless steel" very often the assumption is that high-grade steel is an indestructible, extremely resistant material. Even in hospitals, numerous users expect that instruments of high-grade steel have to be everlasting. They are surprised if they are told, or find out for themselves, that even high-grade steel can be susceptible to many different kinds of mechanical, thermal or chemical attacks.

Understanding the material and its characteristics, together with knowledge regarding correct handling, will result in achieving trouble-free, long-lasting use of high-grade steel instruments.

Only a very limited number of stainless steel types can satisfy the requirements asked for by the user of surgical instruments. Due to their special alloy, high-grade steels used for surgical instruments are characterised by the fact that they form specific passive layers as a protection against corrosion. These protective layers can, however, be damaged by external influences which will harm the instruments. Only to a limited extent are high-grade steels resistant to the attack of aggressive waters, e.g. with a high chloride content. In particular, chloride ions can cause pitting or even stress corrosion cracking.

Users of surgical instruments can be assured that manufacturers take great care not only regarding the selection of the correct steel types but also regarding the steel processing. To maintain the value of the instruments, the user must provide continuous expert care and correct preparation.

Instruments for microsurgery and laparoscopy require especially careful preparation. These instruments are very delicate and have extremely fine elements for operating reasons. Therefore they are extremely sensitive to improper mechanical strain when in use, preparation or transportation. It has also been proved that in most cases, damage can be traced back to mechanical influences – and mostly, such damage is irreparable.

Components which do not have to be sterilized, such as columns, foot switches, cables etc. are not discussed here. Special instructions for the preparation and treatment of MIS-instruments, flexible and rigid endoscopes are also given.

The working group for hospital hygiene recommends. "In the interest of patience safety, the hygienic requirements for endoscopic surgery should be the same as in conventional surgery. Thoroughly cleaned and sterile instruments are allowed for use in endoscopic surgery. This assures that an important part of quality assurance requirements are met".

MIS-instruments, which are used with pressure (gas insufflation) during an operation, soil heavily. Therefore they need special attention for cleaning: Either they can be dismantled or they can be rinsed through a channel.

Endoscopes are precision instruments for observation of an illuminated preformed body cavity or body opening (e.g. bladder, intestine, abdominal cavity, bronchi, joint cavities, vessels). As a result of the various endoscope designs, different materials are used for their production, the different characteristics of which must be taken into consideration.

Single-use instruments should be fundamentally used only once! Therefore no additional comments on reprocessing single-use instruments is discussed.

Elastic instruments of rubber or plastic, as used for example in urology, anaesthesia or gastroenterology, also require special preparation methods.

Recommendations for the preparation and treatment of breathing systems refer only to those parts conducting gases, such as:

• breathing tubes
• breathing bags
• breathing masks
• folding bellows
• connection pieces

Maintenance of instruments involves

1. Meticulous cleaning
2. Decontamination
3. Disinfection
4. sterilisation

Cleaning is defined as the Removal of visible dirt, soil, organic matter or other foreign material.It is a removal rather than a killing of microorganisms.

May be accomplished with

• water
• Mechanical action
• Detergents
• Enzymatic products

Importance of Cleaning

1. Renders disinfection or sterilization effective.
2. Brings about a 4 log reduction in contaminating organisms

Decontamination is defined as a Process both Physical and Chemical or either , to remove or reduce contamination from infectious organisms or other harmful substances

Cleaning and Decontamination may be

• Manual
• Automatic washer/decontaminator- which is safer to personal, but is not easily available, and cannot be used for some instruments.

Enzymatic Products are Catalysts that enhance or loosen dried or hard to remove debris Usually added to water or cleaning solutions

Preparation for disinfection and cleaning[edit | edit source]

Disinfection of soiled instruments not only helps to preserve the instruments themselves, but also serves to protect those persons responsible for their transportation and cleaning. The guidelines of the Robert-Koch-Institute state: "Wherever possible, instruments should be disinfected and cleaned immediately after use. Any soil left to dry will make eventual cleaning much more difficult and could result in damage to the instruments. If necessary, instruments should be taken apart, allowing the disinfectant to cover all surfaces."

Personal Protective Attire[edit | edit source]

1. Scrub suits under a moisture impervious gown or important suit
2. A Mask and goggles/full face shield – protection form splashes or aerosolization
3. Heavy duty long cuffed gloves
4. Isolate the cleaning area from rest of the operating room.

Selection of a cleaner/Detergent[edit | edit source]

1. Detergents should Facilitate loosening of Debris and not damag
   • Instruments – Enzymatic cleaners are best
2. Should rinse of without residues
3. PH<7 – best for inorganic debris such as urine hard water scale
4. PH>7 – organic soil such as blood, faeces,
   • - Stainless steel instruments
5. Follow manufactures instructions at all times

Topical antimicrobials intended for skin antisepsis is not to be used

For disinfection of the instruments either moist heat or chemical disinfection can be used. Moist heat is preferable, providing the instruments are suitable for treatment in this manner.

Unused instruments have to be prepared in the same way as used instruments; therefore those instruments have to be opened or dismantled.

Occasionally, corrosive caustic agents and medicines (e.g., silver nitrate, iodine preparations, albotyl and mercury components) are used in operations and for medical treatment. Remnants of these substances have to be removed immediately.

Under no circumstances must instruments be stored in physiological saline solution as prolonged contact causes pitting and rust.

Undue "dropping" can cause damage to the instrument. Hard metal tips on scissors may be chipped or small, delicate clamps can be deformed. In order to avoid this, carefully handle and deposit the instruments after use.

To avoid encrustation and corrosion, return in dry condition and to CSSD, the instruments must immediately be subject to machine treatment. Therefore "dry" has to be taken word-to-word. Even small amounts of fluids (e.g. dishes with physiological saline solution) should be avoided on the goods for return.

For this treatment, deposit the instruments on suitable trays, e.g. perforated sterilizing trays. For effective cleaning, hinged instruments have to be opened (such as scissors, clamps, gouge forceps).

For return in wet condition to CSSD, instruments have to be immersed into a combined disinfecting and cleaning agent. Therefore use only non-corrosive agents in prescribed concentrations. Water alone is not sufficient.

Instruments should never be left overnight before cleaning as the risk of causing permanent damage increases with the length of time between use and preparation.

Handles and cables for HF-surgery have to be prepared like surgical instruments.

Dismantled tubing sets for cooling liquid and spray nozzles have to be rinsed immediately with water from the rinsing bottle and checked for leakage

MIS-instruments and rigid endoscopes have to be dismantled according to the manufacturer's instructions. This equipment has to be placed in special containers designed for this type of equipment.

Articles which are declared "for single use only" have to be disposed.

Dried residues are crucial, especially for operative endoscopy, because of the difficulty of removal in small lumens and may lead to dysfunction of the links. Therefore these instruments have to be processed immediately after use. It is recommended to use a 3% solution of hydrogen peroxide for rinsing the HF-instruments to remove the coagulated tissues that may form during longer operations.

Instruments should be transported in special containers or retaining devices to avoid damage to the instruments.

Dismantle elastic instruments and breathing systems according to the manufacturer's instructions. Cones, sealing surfaces, thread connections and valve plates have to be carefully handled and protected against mechanical damage.

Prior to preparation, completely remove breathing lime from the absorbers. Data readers have to be prepared only according to the manufacturer's instructions.

Manual disinfecting and cleaning[edit | edit source]

For manual preparation, instruments have to be immersed into a combined disinfecting and cleaning solution with proven disinfecting effect.

The instructions of the manufacturer have to be strictly followed regarding concentration, temperature and exposure time. Special attention has to be paid to the manufacturer's instructions with regard to material compatibility of instruments not made of high-grade steel.

Use fresh disinfecting and cleaning solutions every day. The following problems may occur due to using the same solution for too long:

• risk of corrosion due to soiling
• risk of corrosion due to increasing
• decrease of disinfecting effect due to excessive dirt concentration

Instruments with a narrow lumen (tubings, cannulae) or with cavities are generally difficult to prepare. One must, therefore, take care that the passages are free and that the inside is completely in contact with the solution.

If powdered products are used, completely dissolve the powder first. Only then should one immerse the instruments since undissolved particles may lead to clogging of the narrow lumen and discoloration of the instruments.

After chemical disinfection and cleaning, the instruments must always be rinsed well under running water. Rubber and elastic plastic needs longer rinsing time than other materials. Any remaining residue have to be removed manually with minimal trauma to the instruments (no metal brushes, no scouring agents!). In order to avoid water spots, a final rinse with demineralized water is recommended. Finally, the instruments have to be dried immediately.

Water on the surfaces of elastic instruments made of rubber or plastic may may cause white spots to appear which can only be removed by drying.

If, after manual cleaning, instruments are chemically disinfected instead of being sterilized, a separate disinfectant has to be used.

The instruments must then be rinsed thoroughly with sterile demineralised water and dried immediately.

If pneumatic air is used for drying, make sure that the air flows through a sterile filter.

Simple tools can be prepared like surgical instruments.

MIS-instruments and rigid endoscopes have cavities and channels which are difficult to clean. Careful preparation of these instruments requires:

• Removing the seals/washers
• Opening the stopcocks
• Dismantling according to the manufacturer's instructions

Use brushes with plastic bristles, cleaning guns or clean soft cloths to avoid damage due to unsuitable cleaning accessories. Drying with compressed air is very gentle and effective, and therefore it is the preferred method of drying.

When immersing the endoscope into the cleaning and disinfection solutions, make sure that all air bubbles escape from the cavities by moving the instrument, or by holding it in a sloped position, thus guaranteeing complete wetting of the surface.

Use a wooden applicator with cotton wool soaked in alcohol to gently rub off any dirt on windows or glass surfaces, otherwise use a neutral detergent (hand washing liquid).

MIS-instruments and rigid endoscopes with encrustation which could not be removed through intensive cleaning (e.g. brushing, ultrasonic treatment) have to be discarded because it is not possible to ensure the function of the device.

Comment:

Instruments which cannot be dismantled and have a rinsing connection should be rinsed thoroughly with a cleaning-/disinfection agent. Observe the distal end to ensure that the fluid is flowing out.

Elastic instruments with lockable cavities, such as bellows and breathing masks have to be cleaned and disinfected in closed condition thus avoiding the penetration of liquid into the cavities.

To avoid damage on diaphragms and functional parts of the breathing system, no compressed air should be used for cleaning.

Machine Disinfection and cleaning[edit | edit source]

The instruments should preferably be returned in dry condition to the machine preparation. At the return in wet condition the danger of protein-fixation exists from several chemicals. Therefore use a disinfectant with a cleaning component. These agents should be either low-foam producing disinfectant or else the instruments have to be thoroughly prewashed as foam development in the cleaning and disinfecting machine can reduce the cleaning results. This comment also applied to instruments with problem encrustation (encrustation by HF-instruments, remnants of filling materials or similarities) that have been pre-treated with or without ultrasonic.

The disinfection of instruments in a cleaning and disinfection machine is preferably done thermally at a set temperature and time (e.g. 93^oC/10 minutes). The methods of cleaning and thermal disinfection are distinguished between epidemic-hygiene aspects and general-hygiene aspects.

Chemothermal procedures are used for thermolabile instruments or material.

Methods under epidemic-hygiene aspects require the disinfection in the first phase. Alkaline detergents are preferably used for cleaning. Methods under general-hygiene aspects require separate phases: first the cleaning and later the disinfection. As detergents pH-neutral and/or enzymatic products are preferred. In both cases detergent and program have to be tuned.

A good cleaning during the instrument preparation helps to maintain the value of the instrument. Therefore methods are preferred which are optimized for cleaning and which run the cleaning separately from the disinfection in the content of a general infection prophylaxis.

When using cleaning agents, and if necessary, disinfection agents, it is recommended to strictly follow the instructions of the manufacturer regarding exposure time, concentration and temperature. Using the correct concentration does not only guarantee a perfect disinfection and cleaning result, but also the most careful treatment of the material. Automated fluid dosing have to be supervised.

In the presence of increased chloride concentrations in water, pitting can occur on the instruments. Such corrosion can be avoided through using alkaline products during the cleaning phase and demineralized water for the final rising.

The inflowing water for the cleaning phase should be cold prior to beginning the main cleaning phase. Warm water, especially with temperatures over 45^oC, will lead to coagulation of proteins and therefore lead to cleaning problems.

With machine cleaning, special attention has to be paid to the following:

• Trays and machine must be correctly loaded
• Hinged instruments have to be opened, thus guaranteeing thorough cleaning in the joint.
• Do not overload the perforated trays, so that all instruments can be well rinsed.
• Place large and bulky instruments properly on the trays thus avoiding "shadows" on other instruments.
• A thorough internal flow has to be guaranteed with instruments having long, narrow cavities (tubing, cannulae, breathing systems). Use special inserts with rinsing-devices which are designed for the instruments.
• Place instruments depending on their mechanical construction in such a way that they cannot damage each other.

Colour-anodised aluminium instruments may lose their colour and their coding function if normal machine preparation methods are used. It is possible to clean colour-anodised instruments together with the other instruments by using pH-neutral detergents at lower temperatures and demineralised water for the final rinse (also for the thermal disinfection).

Residues from the cleaning phase have to be totally removed in the subsequent rinsing procedures, otherwise spotting and/or discolouration may occur. Additional use of a suitable neutralising agent improves the rinsing results especially with alkaline detergents.

Should corrosion occur on surgical instruments due to bad water quality, then the rinsing temperature should be limited to 70-75^oC for thermal procedures under epidemic-hygiene procedures the final rinsing on thermal disinfection should be demineralised water. When using demineralised water for final rinsing then corrosion, water spots and also discolourations depending on the reasons will be avoided. No temperature limit must then be observed.

If the drying of the machine is not sufficient then dry the instruments manually.

MIS-instruments and rigid endoscopes have to be dismantled for machine preparation according to the manufacturer's instructions. Seals/washers have to be removed and stopcocks opened.

Machine preparation should be done only if recommended by the manufacturer. In order to avoid damage, secure the parts safely. The maintenance by machine is only allowed with a machine which is proved to be a cleaning and disinfection machine for this usage. The machine must thoroughly flush inside any instrument lumen.

Instruments with encrustation of coagulation which could not be removed through intensive cleaning (e.g. brushing, ultrasonic treatment) have to be discarded because it is not possible to ensure the functionality of the instrument or that sterilisation will be effective.

Elastic instruments with lockable cavities, such as bellows, breathing masks etc., have to be cleaned and disinfected in closed condition thus avoiding the penetration of liquid into the cavities. To avoid over-stretching of the edge of the mask, remove the nipple prior to preparation, press out some air and replace the nipple.

Elastic instruments, made of PVC for example, with low temperature resistance have to be disinfected, cleaned and dried at max. 65^oC.

Care has to be taken with rubber instruments because residues of cleaning agents lead to irreversible damage by subsequent drying and sterilisation. The surface of the material depolymerises and gets sticky. Latex-coating dissolves under blistering.

Especially serious are residues not completely flushed out of functional parts of the breathing system. Furthermore, all parts have to be completely dry as remnants of moisture may lead to functional troubles.

Elastic instruments may not be dried above 95^oC; higher temperatures considerably shorten their life span.

Functional parts of breathing systems are specially designed by the manufacturers of ether units. Preparation can, therefore, only be performed according to the manufacturer's instructions.

Ultrasonic treatment[edit | edit source]

Ultrasonic treatment is particularly suitable for cleaning instruments of high-grade steel. Delicate instruments (microsurgical instruments, dental instruments) can be carefully and thoroughly cleaned by ultrasonic treatment. Powerful machines for ultrasonic treatment are able to remove encrustation in inaccessible places.

Ultrasonic treatment is used for:

• Effective mechanical help for the manual cleaning processes
• For pre-treatment of instruments with encrustation that is dried on before machine cleaning and disinfection
• In special designed component parts for tunnel washers which can be ordered optionally

In order to achieve optimum efficiency of the ultrasonic treatment, please observe the following.

• Fill the bath following the instructions by the manufacturer,
• Add a suitable cleaning agent or a combined cleaning and disinfecting agent,
• When using disinfecting and cleaning agents, make sure that the concentration, temperature and time of sonication recommended by the manufacture are correctly maintained,
• It is advised to fill the bath with warm water because temperatures over 40^oC promote degassing and cleaning.

Even with a properly prepared bath, faults can arise. These can be avoided by observing some principle rules:

• Instruments have to be completely covered by the cleaning solution. Non-immersed instruments will not be cleaned.
• Hinged instruments, e.g. scissors, have to be opened.
• Only trays which do not affect the ultrasonic treatment should be used (e.g. trays made of wire)
• Large and bulky instruments such as lead hands or kidney trays must be placed in such a way that there are no wave shadows or inactive zones. Place such items either vertically or put them on top of the other instruments.
• Trays may not be overloaded,
• An excessively dirty solution in the ultrasonic bath decreases the cleaning effectiveness and increases the risk of corrosion. Depending on the frequency of use, the solution has to be renewed at regular intervals.
• Ultrasonic treatment times of approx. 3 minutes have proved to be efficient for cleaning at frequencies of at least 35kHZ.
• In the case of simultaneous disinfection and cleaning, suitable products should be used paying attention to exposure concentration and time.

After ultrasonic treatment, the instruments have to be thoroughly rinsed either manually or by machine. Rinsing has to be performed with clear water of at least potable water quality or, better still, with demineralized water in order to avoid water spots.

The instruments should then be thoroughly dried.

To avoid damage, micro-surgical instruments have to be deposited on special racks.

Ultrasonic treatment is only allowed for those parts of MIS-instruments or rigid endoscopes which are suitable for this procedure according to the manufacturer's instructions (e.g. no optical systems).

MIS-instruments and rigid endoscopes with coagulated encrustations caused by using HF-treatment and could not be removed through intensive cleaning have to be discarded because it is not possible to ensure the functionality.

Elastic instruments are not suitable for ultrasonic treatment as ultrasonic waves have no effect on elastic surfaces.

Functional parts of the breathing system can also not be prepared in an ultrasonic bath.

Care and maintenance[edit | edit source]

Instruments with joints or ratchets have to be treated with a suitable autoclavable lubricating agent during the cleaning process.

These lubricating agents prevent the friction of metal on metal and preserve smooth function of the instruments thus avoiding corrosion by friction. Furthermore, constant use of such agents prevents "sticking" of the hinged parts.

The lubricating agents can either be applied manually or during the final rinsing in the machine.

In any case, it is indispensable that threads, joints, etc. that are difficult to access are directly treated with each preparation.

MIS-instruments and rigid endoscopes contain different materials like plastic or rubber that may be affected by the lubricant. In general, lubricating agents applied (by machine or manually) to optics, seals and current-carrying parts can lead to massive troubles and dysfunction and therefore should not be done. This includes instrument milk.

Joints, threads, sliding surfaces and non maintenance-free stopcocks may have to be treated with special oil or special grease according to the manufacturer's instructions.

The only necessary maintenance on flexible endoscopes is to treat the valves with silicon oil before inserting them into the valve housing. Do not spray them with care agents as the propellent gases will damage the instruments.

Only silicon oils and grease-free gels should be used as lubricants according to the manufacturer. Agents containing Vaseline or paraffin cause swelling or softening of rubber parts.

Refrain from treating elastic instruments and breathing systems with lubricants prior to sterilisation. Special care and maintenance measure are prescribed by the manufacturer, should the need arise.

Elastic instruments of silicon rubber may not be treated with silicon because of swelling which makes them inoperable. Under no circumstances use paraffin agents for rubber and latex instruments; this prevents them from swelling up.

Inspection[edit | edit source]

Each surgical instrument is designed for a specific purpose. Inspection has to be carried out to ensure that they still function as they should. If in any doubt, a reliable manufacturer can advise you on suitable inspection methods.

After each cleaning, the instruments have to be macroscopically clean, i.e. free of visible protein remnants and other contamination.

Prior to functional inspection, surgical instruments with movable parts should be cooled down thus avoiding metal friction leading to corrosion. Before carrying out functional inspection, oil any instruments with joints, ratchets or threads.

Instruments with non-traumatic toothing have to be specially inspected, and, if necessary, the non-traumatic toothing cleaned manually to keep the non-traumatic function.

Worn out or damaged instruments should be removed for repair or replacement. Corroded instruments should be discarded immediately as these can cause contact corrosion even on a perfect surgical instrument.

Especially fine and delicate instruments are inspected under the magnifying glass. In order to avoid damage during transportation, place the instruments in specially designed racks or use special holding devices to prevent them from slipping.

Faultless surgical instruments should not be packed together with instruments having damaged surfaces. Older instruments with chipped chromium and/or nickel coating may cause discoloration or corrosion on high-grade surgical instruments. It is, therefore, recommended to discard such instruments or pack them separately.

Handles, cables and cables for neutral electrodes for HF-surgery have to be checked for faultless function.

(Caution: defective contact). It is compulsory to sort out defective parts.

Instruments given to repair have to be completely decontaminated due to hygienic reasons.

Stains on instruments are due to improper preparation. Because stains are usually found during inspection, the reasons hereof are discussed now. Cause of such stains or spots can be:

• Insufficient mechanical or manual cleaning.
• Unsuitable cleaning, disinfecting and care agents.
• Failure to observe the dosage instructions for cleaning, disinfecting or care agents.
• Residues of cleaning and disinfecting agents – insufficient rinsing.
• Poor water quality.
• Water-soluble residues e.g. washing agent in textile cloths for wrapping,
• Residues in the sterilising steam (exceeding the index for contaminants in steam)
• Remanants of medications, marking pens or chemo-indicators.
• Procedural faults e.g. not cleaning brand-new surgical instruments prior to sterilisation.

These and other causes for spots on surgical instruments show the complexity and difficulty of the problems dealt with here. To facilitate tracing and identifying the cause for such stains, it is recommended to cooperate with competent manufacturers. By making use of the company's service, you will not only take advantage of their practical experience but their well-equipped laboratories as well.

To avoid permanent damage, instruments with residues on the surface have to undergo a special treatment. The method of treatment depends on the cause of the stains. In order to avoid damage and subsequent corrosion due to metal friction, under no circumstances use metal brushes or metal sponges to remove stains.

Prior to sterilisation, the surgical motor line with accessories should undergo a functional inspection according to the manufacturer's instructions.

Simple tools are inspected as general surgical instruments. In order to avoid damage during transportation, store the tools in special racks or place them in suitable holding devices to prevent them from slipping.

The leak test for tubing sets for cooling liquid can be carried out by means of a clamp and a large syringe filled with water. Fill the tubing with water; close one end with the clamp, and insert and empty the filled syringe in to the other end.

The perfect function of MIS-instruments and rigid endoscopes can be ensured only through an intensive functional inspection. All dismantled instruments have to be assembled together following the instructions of the manufacturer prior to functional inspection.

Exchange or renew working parts and damaged components before sterilisation. Especially test insulation for damage.

Instruments with encrustation of coagulation on working parts, which still exist in spite of cleaning, have to undergo a special manual treatment as described. If this does not help, then discard the instruments, endoscopes and accessories and replace them with new ones.

To avoid damage to optical systems, clean them carefully with a cotton swab moistened with alcohol. If this does not remove clouding on the optics, return the part to the manufacturer for inspection. Damage can be avoided by using wooden or plastic handled applicators; metal is not suitable.

Light-carrier in telescopes and fibre-optic cables have to be checked for optical fibre breaks. To do this, take one end of the fibre optic cable, hold it against the light and look into the other end. Little black spots indicate breaks in the fibres. A large number of breaks reduces the light output. Such fibre-optics as well as endoscopes with surface damage and surface deformation should be sent for repair.

Breathing systems have to be inspected according to the manufacturer's instructions.

Elastic instruments have to be inspected according to their function and range of use. The most important inspections are:

• Bellows have to be undamaged and airtight
• Filling system of the bellows must not show any leakage
• Lumina of catheters and probes have to be free
• Connections have to meet functional safety
• There should be no changes of design, e.g. radius of curvature of tracheal tubes

Elastic instruments with faults or damage have to be replaced. Frequent problems are

• Detachment (blister forming)
• Cracked surface
• Sticky surface
• Hardening
• Porous surface
• Discolouration

To prevent premature failure, take care that elastic instruments are stored in a dry place without being kinked or overstretched.

Disinfection[edit | edit source]

Disinfection – Process that eliminates many or all pathogenic microorganisms with the exception of bacterial spores from inanimate objects and surfaces.

Sterilization – destroys all microbial life

Factors affecting disinfections are:

1. Previous cleaning of objects
2. Type and level of microbial contamination
3. Concentration and exposure time to germicide
4. Physical configurations of the object [E.g., contains crevices, hinges and bureaus]
5. Temperature and PH of disinfecting process

Susceptibly in decreasing order[edit | edit source]

• Bacterial spores
• (Bacillus subtilis, Clostridium)
• Mycobacterium
• (Mycobacterium Tuberculosis)
• Non-Lipid or small viruses
• (Poliovirus, Rhinovirus)
• Fungi (Cryptosporidium, candida)
• Vegetative Bacteria
• (Staphycocus, Pseudomonas, eterococi, MRSA,
• Lipid or medium sized viruses
• (Hepatitis B, HCV, HIV, HS, CMV, RSV)

Classification of Patient care Items[edit | edit source]

Spaulding classification (1968) uses

1. nature of items.
2. manner in which used
3. degree of risk of infection

Critical items[edit | edit source]

1. High risk of infection if contaminated
2. Enter sterile tissue or vascular systems or have blood flowing through them
3. Sterilisation is required.

Ex: surgical instruments.

• Implants.
• Needles
• Endoscope accessories
• Catheters—vascular\ Urinary
• Laparoscopes.

Semicritical Items[edit | edit source]

Contact with mucous membranes and Non-intact skin

Minimally receive high level disinfect ion (HLD ). May also be sterilised

Some semi critical items such as Hydrotherapy tanks thermometers require only intermediate level disinfect ion

Examples--- Endotracheal tubes, Endoscopes, Bronchoscopes, Laryngoscopes, respiratory and reusable anaesthesia equipment, diallers, transducers, thermometer, hydrotherapy tanks.

Non-critical items[edit | edit source]

Come in content with intact skin should receive intermediate or low level disinfection.

Eg: Stethoscopes, blood pressure tourniquet cuffs, Echo leads, bed pans linens environmental surfaces as table tops, beside stands furniture floors etc.

LEVELS OF DISINFECTION:

High-level disinfections (HLD)

• Eliminates all microorganisms except large population of bacterial spores
• Achieved by immersing for specified period in a chemical agent
  • a) disinfection
  • Sterilant
• Some high level disinfectants with prolonged contact act as a sterilant.
• Thermal HLD is accomplished with pasteurisation

Intermediate Level Disinfection

• Inactivates vegetative bacteria including micro bacteria, most viruses, fungi but not spores
• Used for semi critical items
• Achieved by immersing in specified chemical agent or by surface disinfection Low-level disinfection
• Used on Non-critical items
• Kills vegetative bacterial and some viruses and fungi but not tubercle bacilli

Accomplished by surface cleaning or disinfection by washing or cleaning with specific chemical agents

Chemical Agents - Germicide

Chemical used for HLD

• Exposure time = >- 20 minutes 12 minutes for cidex OPA
• 2% - 3.4% Gluteraldehyde
• 0.08% - Peroxyacetic acid and 1% H2O2
• 7.5% hydrogen peroxide / 0.85% phosphoric acid
• 0.95% Gluteraldehyde / 1.64% phenol / phonate
• 0.2% perantic acid ((stasis 20)
• 0.55% Orthophthaldehyde (Cider OPA as HLD only)
• Damand – Release chlorine dioxide (limited use)

ILD

• Exposure time = < 10 minutes
• Ethyl or isopropyl / alcohol (70% - 90%)
• Phenolic germicidal detergent solution
• Iodophor germicidal detergent solution
• Sodium hypo chloride (5.25% house hold bleach) 1:50 dilution

Low-level Disinfectants

• Exposure time = < 10 minutes
• Ethyl or isopropyl / alcohol
• Phenolic germicidal detergent solution
• Iodophor germicidal detergent solution
• Sodium hypo chloride (5.25% base hold bleach) 1:500 dilution (100 ppm)
• Quaternary Ammonium germicidal solution (disinfectant, not antiseptic concentration)

Disinfectant of HBV

• 2% Glutaradehyde : 0.55% orthoph thalaldehyde
• Iodophor (80 ppm)
• 70% Isopropyl alcohol
• 80% Ethyl alcohol
• 0.3% H2O2
• Sodium hypo chlorite 1:100 dilution

Disinfectants of HIV

• 2% Glutaradehyde : 0.5% orthophthalaldehyde
• 0.3% H2O2
• 50%Ethyl alcohol
• Phenolics
• Sodium hypo chlorite 1:100 dilution

Chemical High Level Disinfection

Important variant is contact time - If contact time of 10 hours is used a disinfectant may be used as sterilant

Factors influencing chemical agent include

• Organic load present on items to be disinfected
• Type and level of microbial contamination
• Precleaning, rinsing, drying on items
• Active ingredient of chemical agent
• Concentration of chemical agent
• Physical Configuration of the items (eg crevices, lumens)
• Exposure time of chemical agent
• temperature and PH of the chemical agent
• Hardness of water
• Precense of surfactant

Immersion Recommendations

• Items should be completely increased
• Lumens should be flushed with germicide
• Recommendation for immersion range from 12-45 minutes
• For HLD in 2% activated Gluteraldehyde is a minimum 20 minutes at 68% F (20`C) when used on meticulously cleaned instruments.

Vapour exposure

• Protective apparel for personal
• Vapours are toxic therefore covered containers and adequate ventilation is necessary
• Permissible exposure limit is 0.2 ppm per exposure

Automatal Reprocessing

AERs Standardise the disinfection process and decreased personal exposure to disinfectants. No currently available AERs provide cleaning of endoscopes

Pasteurisation[edit | edit source]

• Pasteurisation my be used for thermal HLD
• It is suitable for HLD of some anaesthesia equipment, respiratory therapy and other semicritical equipment
• In a pasteurisation – all items to be disinfected are exposed to a hot water bath, heated to 160`-180` F for a minimum of 30 minutes
• It kills all microorganisms with exception of spores
• Commonly used Disinfectants
• Gluteraldehyde 2% solution
  • Widely used easily available
  • PH of 7.5 – 8.5
  • Shelf life after activation is 14 days. Using a surfactant may increase shelf life
  • Different contact times and different groups
    • 10 minutes – kills both gram +ve, -ve and viruses
    • 4 hours – sterilisation including resistant spores
  • Protective gloves needed for personal to avoid allergies
  • It does not damage lensed equipment

Formaldehyde - Broad spectrum antimicrobial action only under optional conditions of

1. Concentration
2. Exposure time

At atmosphere pressure and temperature of 50`C it has limited spermicidal action

Boiling Water - Effective disinfection process

• Kills
  • Vegetative bacteria including M tuberculosis
  • Some viruses (including HBV and HIV)
  • Some spores
• Purpose designed water boiler is needed
• hinged lid
• Perforated tray with rising / lowering level

Sterilisation[edit | edit source]

General[edit | edit source]

Sterilisation conditions as well as units have to be in conformity with valid quality standards (EN-or DIN-standard).

Follow the sterilisation instructions of the manufacturer.

Sterilisation of accessories, as well as sterilising packings, has to meet the requirements of both the instruments as well as the sterilising method used.

Process that destroys all forms of microbial life – including spores on inanimate surfaces

Sterilisation and sterility are absolute terms

Measured as a probability of sterility – sterility assured level (SAL)

Defined as Log 10 number of probability of survivor or a single SAL of 6 indicates 1in one million probability of a spore or microorganism's survival

Sterilisation a) Physical – dry and moist heat in a gravity/prevacum container

b) Chemical – Ethylene oxide, gas plasma, H2O2

Pre cleaning is also prerequisite of sterilisation as for disinfections

Autoclaving[edit | edit source]

Normally, autoclaving is performed with saturated steam at 134^o. For articles with reduced thermal-stability a temperature of 121^oC can be used at a longer time.

The sterilisation procedure has to be standardised suitable for the goods to be sterilised. Sterilising packings have to meet the valid standards with regard to quality and application of the packings and have also to be applicable to the procedure selected.

Steam used for sterilisation has to be free from any contamination and should neither impede the process nor do damage to the steriliser or the goods to be sterilised. In order to guarantee this, the limits for the quality of boiler feeding water as well as the condensate, should not be exceeded. Otherwise, contaminants such as rust particles from the conducting system may cause corrosion or a too high content of silicic acid may lead to discolouration of the instruments.

Due to heating and cooling down during the sterilisation process, a surgical instrument with a closed ratchet may suffer from tension stress which causes stress cracking in joints or deterioration of the clamping force. Therefore, such instruments have to be sterilised either in open condition or closed on the first ratchet only.

The loading weight of perforated trays filed with instruments should not exceed 10 kg. By this way excessive condensate production during sterilisation is avoided. Drying is facilitated by wrapping the perforated trays with a cloth within the container or external paper packing.

If heavy sets are unavoidable, the instruments should be distributed among several perforated trays. In addition, special measures may be necessary for drying.

After sterilisation, instruments have to be stored dry until used again. Instruments as well as the inner covering of sterilised goods have to be absolutely dry after having cooled down to room temperature.

All components of the surgical motor line, meant for sterile application, can be autoclaved at 134^oC. Refer to the manufacturer's instructions. Special instructions of the manufacturer have to be observed for storage during sterilisation.

Hoses for compressed-air have to be protected against pressing during sterilisation.

MIS-instruments and rigid endoscopes can be sterilized by conventional methods in suitable packing. Optical systems suitable for autoclaving should be processed at 134^oC instead of at 121^oC due to the shorter thermal stressing. To avoid damage of optical systems by sterilization, they should be stored carefully following the instructions of the manufacturer.

Elastic instruments with and without bellows made of silicon and natural latex are suitable for autoclaving. Due to the shorter thermal stress, preference is given to a processing at 134^oC. Items of thermoplastic materials (plastic) may only be autoclaved if recommended by the manufacturer.

When elastic instruments are autoclaved, take care that the cavities, e.g. edge of mask, bellows, are open in order to avoid damage due to changes in pressure. Prior to sterilization, cavities closed with a valve (e.g. bellow catheters) have to be suctioned free of air and water by means of a syringe.

Functional parts of breathing systems can be autoclaved at max. 134^oC. Cavities must not be closed in order to avoid damage to the valves.

Dry heat Sterilisation[edit | edit source]

• Used for anhydrous oils, petroleum products, talcum powder which steam or ETO cannot penetrate
• May be used for instruments that cannot be disassembled
• Products in jars and Canister take long to sterilise
• Exposure times of 6-4 hours needed –
  • it prostrates materials slowly & unevenly
  • microorganism is destroyed slowly
• Minimum time – 6 minutes for unwrapped at 400`F (204`C), to 6 hours at 250`F (121`C)
• Instrument with delicate, sharp, cutting edges are sterilised like this

Low Temperature Sterilisation

• Useful for temperature and moisture sensitive critical medical devices
  • Ethylene Oxide
  • Gas plasma systems
  • Sterns

1. Ethylene Oxide

• Widely used
• temperature and moisture sensitive equipment is ETO sterilised
• Exposure time - > 2 hours of exposure time to ETO at 129`F (54`C) followed by aeration time of 12-14 hours at 55`C, PVC tubes require 24 hours aeration time
• Gas concentration and relative humidity as well as contact time and temperature, relative humidity of at least 35% - to < 85% is needed
• Items should be completely dry before insertion
• At completion the door has to be left open by 2 inches for 15 minutes
• And personal leave the room before unloading
• Chambers with combination of steriliser and aerator is removed only after aeration
• ETO gas is vented outside before opening and removing instruments
• If absorbed on skin – burns or blisters are seen
• If inhaled
  • mucosal irritant
  • Prolonged exposure cause chemical carcinogen effect
• Patients are affected by improperly aerated polyethylene, rubber or silicon
• ETO is mixed HCFC (hydro fluorocarbons in 1:9 ratio) as stabilising agent.

Hot-air sterilisation[edit | edit source]

When surgical instruments are hot-air sterilised, please take care to load and operate the sterilisers properly. To ensure safe sterilisation, the temperature should not be below 180^oC but should also not exceed 200^oC as this may cause structural changes leading to irreversible damage, especially as far as microsurgical instruments are concerned. Instruments with parts of rubber, plastic or textile as well as plastic-coated instruments and handles for electrodes are not suitable for hot-air sterilisation.

The general use of lubricating agents should be omitted prior to hot air sterilisation with the exception of the joints and ratchets of surgical instruments. For this, use paraffin-oil according to the valid pharmacopoeia. Excess oil should be removed because of the occurrence of brown-discolourations due to thermal changes of the lubricating-oil.

MIS-instruments and rigid endoscopes are not suitable for hot-air sterilisation because of the high temperatures.

Elastic instruments are not suitable for hot-air sterilisation. Breathing systems are not suitable for hot-air sterilisation.

Gas sterilisation[edit | edit source]

Gas sterilisation should only be used when no other method is suitable.

Motor components should only be gas sterilised when explicitly recommended by the manufacturer.

Optical systems of nonautoclavable rigid endoscopes may be gas sterilised, however, follow the instructions of the manufacturer.

Goods sterilised with ethylene oxide require sufficient aeration times before being used again. Depending on the goods sterilised and on available aeration

Elastic instruments of thermolabile plastic are not autoclavable but can be gas sterilised if the manufacturer gives instructions about a suitable procedure.

Elastic instruments of rubber and functional parts of breathing systems do not have to be gas sterilised, cause they can be steam sterilised.

Gas Plasma Systems[edit | edit source]

Consist of a single diffusion phase (Hydrogen Peroxide vapours) and plasma stage

Advantages – no toxic residue, no aeration required, simple to operate and fast cycle time of 7 minute

Disadvantages – do not penetrate lumens, inability to process paper, linen & liquids

Instrument placed in a chamber – 59% H2O2 is injected into it vaporised and allowed to diffuse throughout. Then radio frequency energy is allowed to create hydrogen peroxide plasma. At the end of it the chamber is retuned to atmosphere pressure and cycle is complete.

PARACETIC ACID (STERIS) SYSTEM[edit | edit source]

• Liquid immersion sterilisation process that are fully automated
• Sterilant is 35% paracetic acid and an anticorrosive agent supplied in a single dose container. Container is penetrated as the door is closed.
• Temperature of 50`C to 55`C is maintained

Advantages

• no toxic wastes given out
• Cycle time of 30 to 45 minutes is short

Disadvantages

• small number of instruments is a cycle
• Used for immersible instruments only
• No long term sterile storage – called just in time sterilisation
• Expensive

Gamma Ray Sterilization[edit | edit source]

• Irradiation with cobalt 60 – gamma rays – limited to industrial use only
• Industrial use for heat sensitive and moisture sensitive items

Microwave Sterilisation[edit | edit source]

Low-pressure steam with non ionising radiation

Ozone Gas Sterilisation

• Sterilises with oxidation
• It is corrosive to metals destroys natural rubber

Newer homologies

• Vapour phase paracetic acid
• Vaporised H2O2
• Gaseous chlorine dioxide
• Pulsed light

Treatment of brand-new instruments[edit | edit source]

Shipping-packing of brand-new instruments have to be removed and instruments have to be stored in dry rooms, open to air. Temperature fluctuations may otherwise lead to condensation within the plastic packing and thus corrosion.

Under no circumstances store instruments in cupboards or rooms where chemicals are kept which can produce corrosive vapours.

Prior to first use, brand-new instruments have to be prepared. First remove any protective caps or foils. Cleaning, rinsing, lubrication, inspection and sterilisation have to be carried out according to the procedures previously described.

Prior to the first preparation, microsurgical instruments have to be placed in racks or holding devices to avoid damage.

Elastic instruments have to be kept in their original pacing and stored in a dry, cool and dark place. When ordering please keep in mind that in addition to wear through use, elastic instruments are prone to aging even when in storage.

Functional parts of the breathing system frequently contain valves or membranes which can get sticky when stored for a longer period. Such valves or membranes have to be tested and operated before being put to use.

Special information[edit | edit source]

By following these instructions properly, there is no difference in the preparation of instruments with a mirror finish or matte surfaces.

These instructions do not refer to disposable items.

Instruments and cables with optical waveguides can generally be prepared like surgical instruments, if the manufacturers have not given other instructions. Only hot-air sterilisation and ultrasonic baths cannot be used.

Fibre-optic cables should not be bent, nor coiled too tightly.

Cables and handles for HF-surgery can be machine prepared and are autoclavable.

For all other preparation processes, refer to the instructions of the manufacturer.

Water for preparation[edit | edit source]

Instruments must have certain characteristics in order to fulfill their function (e.g. cutting ability of scissors, clamping force of clamps and forceps). Only a very limited number of steels meet these requirements. Unfavourable water composition can, therefore, have a detrimental effect on such steels. Consequently, the quality of water must be taken into account when planning the sanitary installations.

Ordinary water contains dissolved salts contained varies depending on the water purification process. Evaporation of water leaves residues of salty encrustations (lime). Of all water components, chlorides have to be regarded as the most potentially damaging because in higher concentrations they cause pitting on instruments.

The relationships between chloride content in the water and pitting are not predictable in some cases.

In general, the danger of chloride induced pitting rises with

• increasing chloride content
• increasing temperature
• decreasing pH-value
• longer induction time
• rougher instrument surface
• insufficient drying.

Experience shows that with a chloride content up to approx. 120 mg/l (corresponding to 200 mg/l NaCl = sodium chloride) the possibility of pitting is low but rises rapidly with increasing chloride content.

Low concentration of other components can cause brown, blue, grey-black or rainbow coloured discolouration. Such discolouration can be caused by contact with the elements iron, copper, manganese, magnesium and silicon in the water. Generally, there is no corrosion. By immersing or rubbing the instruments with suitable products containing acid (follow the instructions of the manufacturer) such discolouration can be removed to a great extent. In addition to the natural water components, sometimes there are rust particles in the water. Almost always, such rust comes from corroded piping systems. When preparing the instruments, such rust particles deposit on the goods and cause rust spots (extraneous rust) followed by corrosion.

Make it a basic rule to use demineralised water for final rinsing.

Even when using an ion exchanger for demineralisation, tarnishing can occur due to penetration of salicic acid. The remedy is in-time regeneration of the exchanger – consult an expert.

Materials[edit | edit source]

When producing surgical, microsurgical and dental instruments, the manufacturer will use the materials most suitable for the purpose for which the instrument is intended.

In most cases, the demands for high elasticity and toughness, good cutting ability and high wear resistance together with best possible corrosion resistance can only be answered by using metal materials for surgical instruments. Therefore, first of all, stainless and hard enable chromium steels with a chromium content of approx. 13% are used. Instrument characteristics, such as a smooth and homogeneous surface, a matte or mirror finish, and a hardened condition can be achieved with steels. The user has to observe, however, that these instrument steels, listed in national (DIN) and international (ISO) Standards, are generally resistant to chemical and thermal stress as occurring in doctors' practices and hospitals, but are, on the other hand, very sensitive to stress corrosion and chloride induced pitting.

Beside the hard enable stainless chromium steels, non hard enable chromium steels with modified chromium content and rust and acid resistant chromium nickel steels are used. The use of the latter steels is limited to certain instrument types due to restricted mechanical properties.

Due to the application technique and design of the endoscopes, the greatest variety of materials is used. Here are some of the most important ones:

• Rust and acid resistant chromium-nickel steels.
• Surface treated non-ferrous heavy metal alloy e.g. brass, chromium-nickel plated.
• Light metals (e.g. anodised aluminium).
• Non-corrosion resistant steels, e.g. for lacquered modules and single parts.
• Glass for optical systems.
• Ceramic. Cement and adhesives.
• Plastic and rubber.

The combination of these heterogenous materials is, with regard to the preparation of the units, a weakness in the chain of materials. It may, therefore, be possible that special processing, deviating from the ordinary preparation processes, may become necessary. When in doubt, ask the manufacturer should he not have already given recommendations for use.

Elastic instruments and breathing systems also demand a wide variety of materials, similar to those used for endoscopes. I. E. rubber, latex and silicon.

The full scale of materials dealt with in this brochure is used for the motorised surgical devices as far as design, structure and manufacturing is concerned. Stainless, hard enable chromium steels are used for burrs, drills, milling cutters, saw blades and gearing parts as well as sterilisable plastic material for handles, switches, gearing parts or cables and hoses.

Special preparation methods may be necessary for enamelled housing of the unalloyed steel sheet, lacquered colour codes for identification of the gearing on hand pieces or anodised housings of aluminium for hand pieces and angular hand pieces. Heavily used flexible cables, bearings and gearing parts of stainless, but also of non-stainless heat-treatable steels as well as bronze materials require special preparation and lubrication methods.

Should any question or doubt arise, it is strongly recommended to ask the advice of the manufacturers.

Due to chemical or thermal influences during use, preparation or sterilisation, all instruments and units, dealt with in this brochure, can experience surface changes, corrosion or aging.

Surface changes, corrosion and aging[edit | edit source]

Surface changes are visible appearances. Normally, this refers to all kinds of instruments and units, independent of the material. In particular, this refers to removable residues such as adhering or already encrusted residues from operations or other soiling. Through cleaning using special basic cleaning agents, such surface changes can be completely removed without doing any harm to the instruments.

Quite often, yellow-brown to dark-brown blister-like spots show on sterilized instruments and units made of metal and are mistaken as rust. In most cases, such residue can contain high degrees of chlorides which then lead to chloride induced pitting on parts made of stainless steel if the spots are not removed immediately. Such residues are usually found on those places with difficult access for cleaning.

Annealing colours, black tints or water spots appear mostly on metallic instruments and units and hardly ever on rubber or plastic products.

In general, discolouration do not show clearly defined edges. Flowing color shadings or deep and uniform staining (black colourings) can appear. Discolouration does not permanently damage or destroy the instruments or units. Causes can either be the bad quality of water used for cleaning or autoclaving as well as inadequate machine cleaning and installations for steam supply. The only remedy is to check the technical equipment in the house installation, in cooperation with the manufacturer of cleaning, sterilisation and steam supply plants and also together with the manufacturer of disinfectants or cleaning agents.

Water spots are similar in appearance. However, normally they show sharply defined edges and are caused by too high a concentration of minerals e.g. lime or organic substances in rinsing water or sterilisation steam.

The remedy is to use demineralised water for final rinsing and purified steam.

Overloaded sterilising plants may cause increased condensation and consequently increased stains during sterilisation – therefore avoid overloading.

The term corrosion refers to metallic material only. Corrosion is specific to materials and occurs on various metals in different appearances. Almost always the corrosion leads to permanent damage or even destruction of instruments and units.

Any kind of corrosion on surgical instruments and units can only occur due to contact with water, aqueous solutions or steam. Following is a description of the most important kinds of corrosion and their effect, in the sequence of their frequency of appearance.

Pitting corrosion refers only to metallic materials. Unfortunately, pitting can also appear on stainless steels of which not only most surgical instruments are made, but also endoscopes, (although fewer in number), surgical motor line and parts of breathing systems. With all types of steel, pitting is mainly caused by active chlorides (chloride induced pitting). Other halide ions (iodides, bromides) have the same effect. Nonferrous metals such as copper and aluminium alloys can also be damaged by pitting, however, other electrochemical causes may also be the reason.

Pitting means that holes have developed on the surface of the instruments. These holes indicate rust and, with continuous corrosion, get rapidly bigger and destroy the instrument within a short time.

Pitting can only be avoided if instruments that have been in contact with chlorides or other halide ions are cleaned immediately after use. Please note that organic debris also contains chlorides which lead to pitting should these residues stay long enough on the instruments.

Attention also has to be paid to the quality of water used for cleaning and disinfection, especially with regard to its chloride content.

Stress corrosion cracking normally occurs only in steels used for surgical instruments; it can have considerable effects on the life span of the instruments.

The causes of this type of corrosion can lie either in the manufacturing process or in incorrect handling.

In order to avoid damage, it is absolutely necessary that during the complete cleaning phase, all instruments are kept in open condition.

In order to avoid damage such as stress cracks in the joint and a reduction of clamping force, when sterilising such instruments, only close the first ratchet. This prevents stress forces from occurring while heating and cooling during the sterilising process.

Even tiny quantities of chlorides in the water may favour the forming of stress corrosion cracking.

Fretting and crevice corrosion have almost similar causes. Both types of corrosion occur in narrow joints due to chemical or mechanical destruction of the natural passive coating of the high quality steel. In addition, due to lack of sufficient lubrication, metallic abrasion occurs in joint crevices and hinders smooth action of the instrument. In both cases, and together with humidity, rust blisters occur in the crevices.

Contact corrosion can occasionally be observed when surgical instruments are machine cleaned. Metallic contact of instruments and unfavourable cleaning and rinsing conditions, e.g. tap water containing chlorides, can cause rust.

Particularly severe contact corrosion occurs if stainless steel instruments get in contact with non-stainless goods, such as needles, cutters etc. Chromium-plated instruments with chipped surfaces also cause contact corrosion.

With surface corrosion, the total surface of a metal part is relatively uniformly attacked by chemical or other electrochemical influences. The surface can show parts which differ in color to undamaged surfaces. This corrosion takes the form of rust where steels are concerned.

Surface corrosion hardly ever occurs with instruments made of stainless steel.

Instruments, trays and containers of anodised aluminium require a preparation method suitable for the material. Acid or alkaline solutions may cause laminar corrosion which, especially on colored parts, causes "bleaching".

Instruments and units of stainless steel or non-ferrous metal, protected by galvanically applied coatings, show surface corrosion only with damaged protective coatings.

Any kind of corrosion leads to rust on steels. Rust particles are transferred from one instrument to another during disinfection, cleaning or sterilisation, so this transferred rust causes resultant corrosion on the second instrument. If corroding instruments are not separated, further preparation processes promote rust formation on other instruments.

Sterilising steam from rusty steam supply pipes may transport rust particles into the steriliser. This extraneous rust deposits itself on the inside of the sterilising chamber, on the packings, on instrument surfaces. This extraneous rust also leads to resultant corrosion on instruments.

Aging mainly refers to rubber and latex materials used for flexible instruments, such as parts of endoscopes and breathing systems. Aging is a slow going natural process occurring also during storing. The aging process is accelerated by the induction of dry heat with temperatures above 80^oC, by stretching and over stretching when storing as well as by the action of light (e.g. sun light, UV beams). Aging is visible on rubber by discolouration (brownish) or brittleness (cracks on the surface). Plastic also ages: it gets hard and becomes yellow. However, silicon caoutchouc, also called silicon elastomer, does not age.

Another result of aging on rubber, latex and plastic is the so-called swelling which is caused by the penetration of liquid or gases to the surface.

Swelling can be reversible and occurs only temporarily by the induction of volatile solutions or propelling gases of sprays. This also applies if rubber and certain plastic get into contact with ether gases such as halothane. Irreversible swelling, however, occurs by contact with non-volatile oils (paraffin), Vaseline and unsuitable disinfectants (e.g. phenol derivates). Silicon caoutchouc reacts reversibly on propellent gases of sprays and ether gases; irreversibly on silicon oils and solvents.

Typical signs of swelling are soft sticky surfaces as well as damage to thin-walled instruments parts.

Reference[edit | edit source]

1. Favero MS, Bond WW: Chemical disinfection of medical and surgical materials. In: Block SS, ed.: Disinfection, Sterilization, and Preservation, 4th ed. Philadelphia: Lea & Febiger, 1991. p. 617–641.
2. Rutala W: APIC guideline for selection and use of disinfectants. Am I Infect Control. 1900; 18:99–117.
3. Spaulding EH: Chemical disinfection of medical and surgical materials. In: Lawrence CA, Block SS, eds. Disinfection, Sterilization, and Preservation. Philadelphia, Lea & Febiger, 1968. p. 517–531.
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21. Axon ATR, Bond W, Bottrill PM, et al. Endoscopic disinfection. In Working Party Reports, World Congress of Gastroenterology, Sydney, Australia. Blackwell Scientific Publications, 1990. p. 45–50.
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