Surgical instrument manufacturing involves almost 70% stainless steel as basic raw material. The term “stainless steel” is subject to water spotting and staining. The most common problem is a stain cause by a surface deposit, which appears in a number of colors. But once the cause is found and eliminated, the problem diminishes completely.
Stainless steel used for surgical instrument manufacturing involve a number of reasons like it is rust resistant, it can be honed to an extremely sharp edge or fine point. Also it can be hardened for delicacy and preciseness. In order to ensure stainless steel corrosion resistance, a special two-step corrosion process is adopted. But only these procedures alone cannot guarantee the most useful possible life of the instruments.
Water used for Cleaning Disinfection and Sterilization
The drinking water may contain high concentrations of chemical elements that can cause the deterioration of instruments during cleaning. In particular high chloride concentration is to be considered dangerous because they lead to the forming of corrosion holes. The chloride content must be kept as low as possible e.g., not more than 100 mg/l, otherwise, corrosion risks become very high.
Corrosion and stains
Corrosion results from the action of a liquid or gas reagent on a metal or alloy, therefore, risks of corrosion require preventive action and regular tests throughout the life of the instrument.
Water Stains and Halos
Halos are colored surface marks without accurately defined contours. They result from the presence of mineral substances or heavy metal ions in water or sterilization steams. Water stains are similar phenomena but, in general, their contours are sharp. They result from the residue of organic substances in water or from an excessive concentration of mineral substances such as limestone. Deposits can be eliminated by energetic friction or, if necessary, using a non-abrasive cleaner. The best method is to eliminate the mineral salt from the washing or sterilization water (or to use distilled or de-mineralized water for
flushing and pure water steam for sterilization). If the deposits are not eliminated, pitting corrosion may occur. There may also be whitish stains of phosphates, which is characteristic of some cleaning products.
Colored surface residue
Some yellowish brown to dark brown residue is sometimes wrongfully considered to be rust stains appearing on sterilized instruments. Essentially, this is to be found in the least accessible areas during cleaning. Again, energetic rubbing or the use of a cleaning product will remove the stains without leaving any marks. These stains are due to residue, which had set in solidly and resisted cleaning and sterilization.
Instruments preserved in disinfecting solutions not renewed often can also be coated with deposits. During sterilization, these deposits become scale and take on a dark brown color.
Oxidization is unusual on surgical instruments except if they are soaked for long periods of time in concentrated acid solutions. In this case, the surface of the instrument takes on a rusted look: this comes from the formation of an iron oxide film in places. Such Oxidization may rapidly degenerate and become pitting corrosion.
This is the most frequent form of corrosion and consists in the forming of small but often, deep holes in material whose surface is not deeply attached elsewhere. Such corrosion is caused above all by halogen ions (chlorides, iodine, bromides) working on the surface and resulting from saline solutions or other chlorides, from iodine or from dirty disinfecting solutions. Even if contact with halogens is difficult to avoid, to prevent this type of corrosion, instruments should be cleaned as soon as they have been used. Pitting corrosion is often associated with multi-colored stains resulting from organic residue or other incorrectly eliminated residue or that is associated with isolated plaques of corrosion.
Localized corrosion plaques
The mechanism causing such corrosion is similar to that of pitting corrosion and shares many of its characteristics. It appears more particularly on surfaces at articulation points of forceps.
Corrosion by the forming crevasses or caving
This is often the case of metal parts that come into contact with other parts of the same metal or of another non-metallic material, an assembly liable to form an occluded zone: this is often developed in the hidden parts of the instruments. Essentially it appears by the outcrop of rust appearing in narrow cracks. However, it is often easily confused with the residue of operations or cleaning products: Precise identification is only possible by laboratory analysis.
Corrosion by friction or inter-granular corrosion
Austenitic and ferritic stainless steels may be affected by corrosion more particularly at grain joints. The matrix remains unaffected and they often cause the total breakdown of the metal without such a phenomenon being suspected. Therefore, it occurs between the interstices of two parts moving in opposite directions (such as scissors). The cause is a lack of lubrication: dry friction of two parts against one another causes microscopic chips to form, and rust sets in.
Corrosion by contact
This corrosion comes from the close contact between two metals of different compositions in the presence of electrolyte, for instance water. At the contact points, rust stains appear. The corrosion can become very extensive if stainless steel instruments are mixed with regular steel instruments with incomplete or worn out surface protection (e.g., old chrome-plated or nickel-plated instruments whose chrome or nickel film has come away).
Corrosion by fracturing under stress
In the presence of stresses of various origins (welding mechanical or heat treatment) and in chlorinated media, austenitic steels undergo severe transgranular fracturing; ferric steels are less sensitive to this type of corrosion. To avoid damage, it is indispensable keep the instruments in an open position throughout the cleaning process and for instruments with hooks or racks, not to go beyond the first notch during sterilization. The stresses produced by the temperature build-up, followed by cooling, may provoke clef ting or deterioration at the articulation points. However, it is necessary to differentiate between this clef ting and the fracturing by the forcing of the instrument.
Surface corrosion is particularly rare but may be caused by the contact between instruments and strong acids or caustic solutions or by the deposit of surrounding or suspended rust.
In some of the aforementioned cases, rust forms in cracks, clefts or at contact surfaces. If these instruments are not eliminated systematically, degradation will increase on each new utilization cycle. During washing, the rust formed in this way will be transmitted to the other instruments by cleaning products or by sterilization products (rust in suspension) and cause increasing surface corrosion on the latter.
Various rust phenomena
If the steam production installations or piping are in poor conditions, suspended rust particles may appear in the steam. After sterilization, corrosive precipitation may appear at the surface of the instruments or on the conditioning.
|Problem||Deposits or organic substances|
|Solution||Rinse instrument thoroughly and immediately after use: in distilled or de-mineralized water|
COLORED HALO STAINS AND THE SHARP CONTOURS ARE NOT PRESENT
|In flushing water or steam there are iron, copper, manganese etc. are present|
|Solution||Use distilled or de-mineralized water|
|Solution||Check composition of cleaning solutions|
YELLOW TO DARK BROWN COLORS
|Possible cause||Old Cleaning Solutions/ incorrectly cleaned instruments|
|Change baths after each use/ Rinse instruments immediately after use in distilled or de-mineralized water|
|Possible cause||Detergent with low pH content (6 or less)|
|Solution||Use neutral detergent|
|Problem||Metallic coating or plating|
|Metals of different types have been sterilized together such as, for instance stainless steel with silver/ chrome/….|
|Solution||Sterilize only the similar metal instruments together|
|Problem||Excess heat (chromatic oxide)|
|Possible cause||The autoclave is not operating properly or has been set to very high temperature (this can cause metal to lose some of its properties such as strength and hardness, etc.)|
|Solution||Correct the autoclave temperature|
Proper instrument care can increase the useful life of the instrument possible. Proper cleaning, lubrication, correct handling, and storage can increase the useful life of the instrument. In order to ensure the longest useful life possible, regularly inspect your instrument for sign of corrosion, stain, and water.
Storage and Cleaning
Instruments must be left in original packing if not use immediately. Rough handling should avoid and make sure to avoid contact as it may cause scratching of the surface and may damage to finish. Sudden or hard impacts may cause heat-treated instruments with cutting edges to crack.
Instruments must be completely dry.
Sharp edges should not touch each other.
Protect the tip of sharps.
Face all jaws the same way. Set cupped instruments so water cannot collect.
Unlike metal instruments should keep separate.
Cleanliness is the prerequisite in the care of surgical instruments. Any type of material left on the surface of the instruments can lead to corrosion. Blood, chlorides, and salt leave residue that can clog working mechanism. Make sure the instrument is dry thoroughly to prevent moisture. Lubricate the instruments before autoclave and rinse with distilled water. During using the instrument always avoid contact with cutting edges.
Ultrasonic cleaning is the most effective process to clean the instruments. For mixing of the solution, manufacturer recommendation should be followed. While instrument cleaning, do not mix different metal instruments in the same cycle. Make sure that instruments having ratchets and box locks are accessible. If there is any stain or deposits occur remove these with a quality polish. But make sure hat you do not use abrasive powders or steel wool.
Instruments made up of metals can be sterilized through steam, flash, dry heat or gas. To avoid the problems during the sterilizing process, make sure that there is no rust or foreign material in steam pipes. Also, the door seal must be very tight. Using distilled water should carry sterilizing process.
Proper handling can increase the useful life of the instrument when it is used. Make sure there should not be any instrument abuse. Durrani strongly recommend that the instrument should be used only for the designed purpose. Forceps like bone cutting, and ronguers should only be used on bones. Pin or wire cutter should be used on metal.
Scissors are the particularly subject to abuse. Misuse can easily damage the cutting edge and the blades as well. Eye scissors are very delicate and should be used only for the purpose it is made. Pliers and needle holders are two different instruments and should not be used in place of one to other. For needle holders, always match the needle holder to the size of the needle being used. Haemostatic forceps should not be used in place of needle holders. As the haemostats are used as blood vessel clamps only.
Durrani & Co. Cleaning Recommendations for the Instruments
After research of many years and experience of many years, Durrani & Co. has developed the following recommendations for cleaning disinfection and sterilization of its instruments. We ensure you that If you will follow our policy for cleaning, instruments will have a longer useful life.
After the instruments have been used, dip the instruments in a quality soak. But before putting, make sure about blood, tissue, or other debris from hardening in serration’s, box joints, and moving parts.
2. Brush the instruments
After step one, the instruments must be hand cleaned in a solution using nylon brush. While brushing the instruments, make sure that your attention is to the box locks, serrations, and other areas of the instruments.
For proper cleaning of the instruments use only quality detergents or liquid recommended for this particular purpose. Make sure the instrument is in open position when you clean it.
After the cleaning process, the instrument must be thoroughly inspected. Make sure that all the moving parts of the instruments are moving smoothly. Also, inspect sharp edges.
The purpose of the lubrication is to prevent the moving parts from freezing so that your instruments are in good working condition. The lubricant you use should be good water-soluble.
After cleaning and lubrication, the instruments must be dried before sterilization. Autoclave is best recommended for sterilization method.