Stainless steel surgical instruments are made of corrosion resistant high-grade specialty steels. The key word here is “resistant”. Corrosion resistant does not mean corrosion proof. One of the special characteristics of these steels is that the manufacturer forms a "passive oxide layer" on the surface, which protects them 6against corrosion. This makes surgical instruments as corrosion resistant as possible. It is imperative that you maintain the passive oxide layer to prevent corrosion and maintain your surgery instruments in optimal condition. If this is not done the stainless steel will corrode or stain more readily which will reduce the life of the surgical instrument and/or render it useless. Initially, all “stainless steel” surgical instruments have the same corrosion resistance. When strength and hardness requirements are important factors for instrument function, corrosion resistance is generally lower. Increasing the corrosion resistance would soften the stainless steel. Manufacturers of surgical instruments and surgical instrument containers recommend the use of neutral pH cleaning concentrates. Newly developed neutral pH all-in-one or "combination" cleaning concentrates have been shown to be effective in optimizing the efficacy of the "passive oxide layer". This will provide a longer life for stainless steel surgical instruments. More information and studies regarding the "passive oxide layer" of Surgical Instruments is below.
Interpreting "Rust" - Yellow-brown to Dark-brown Stains or Spots
Yellow-brown to dark-brown stains or spots on surgical stainless steel instruments are frequently mistaken for "rust". These residue deposits (stains or spots arranged in groups or along edges or in crevices) are usually the instrument being exposed to result of high chloride content. They will lead to pitting of the surgical instrument surface if not removed. (see Avoiding High Levels of Chloride below) Excessively hard water can contain high levels of salt sufficient to cause stains or spots that appear as rust. Boilers used to generate the steam for steam sterilizers, if not cleaned properly, will produce contaminated steam which can deposit minerals onto instruments during the sterilization process.
Avoiding High Levels of Chloride
- dry and cool instruments as soon as possible following cleaning & sterilization treatments
- whenever possible use purified water (DI or RO) to thoroughly rinse instruments prior to drying & sterilization
- avoid exposing the surface protective layer of the instrument to abrasive conditions & treatments
- minimize the time instruments are exposed to high temperatures
- avoid using agents containing chloride (do not exceed ~ 120 mg/l, 200mg/l NaCl Sodium Chloride - Salt). A common problem is the inadvertent use of NaCl Sodium Chloride - Salt containing solutions do 'soaking instruments in surgery to maintain hydration of debris and prevent encrustation.
ALSO AVOID using cleaning agents containing other halogen ion agents (e.g. iodides, bromides).
Use cleaning agents containing "Nonionic Surfactants" whenever possible.
Virtually all manufacturers of surgical instruments, rigid scopes, flexible scopes, and instrument containers recommend the use of neutral pH cleaning concentrates. Generic Example of this recommendation: Do not use high acidic (pH <4) or high alkaline (pH >10) products for disinfection or cleaning, since these can corrode metal, cause discoloration or stress fractures.
Do not use high concentrations of chlorine bleach to clean or disinfect stainless steel instruments, as pitting will occur. Never use bleach to clean any surgical instruments. The high pH of bleach causes surface deposits of brown stains and might even corrode the instrument. Even high quality stainless steel is not impervious to an acidic bleach solution.
Sort instruments by similar metal for subsequent processing so that electrolytic deposition (galvanic corrosion) due to contact between dissimilar metals will not occur.
Tap water can contain many minerals, which may discolor and stain surgical instruments. It is recommended that de-ionized water be used for the final rinsing to prevent spotting. all-in-one or "combination" cleaning concentrates can be effective in treating unacceptably hard source water and removing hard water encrustation from surgical instruments and equipment. If untreated tap water is used for final rinsing, then the instruments must be dried immediately to avoid staining.
Clean instruments, or apply treatment to prevent the drying and encrustation of debris, as quickly as possible after use. Do not allow blood and debris to dry on the instruments. If cleaning must be delayed, place groups of instruments in a covered container with appropriate detergent or enzymatic solution to delay drying. The use of pre-soaking enzyme foam sprays has been shown to reduce the time expended for manual cleaning and render higher quality outcomes. After surgery, open all box locks and disassemble instruments with removable parts. This will limit blood drying on instruments that may cause them to corrode. The "all-in-one" cleaners and the enzyme-detergent foam sprays deliver a chemical complex to: maintain hydration of bioburden, prevent corrosion, clean the surface, and condition the surface of instruments & scopes. This can significantly reduce manual cleaning and facilitate cleaning the surface of surgical instruments, scopes, and the lumens of cannulated instruments inside-and-one. If used properly, all-in-one enzyme detergent foam sprays and/or all-in-one "combination" cleaning concentrates can render excellent outcomes and facilitate cleaning instruments and scopes inside-and-out. They effectively cleaning the surface while cleaning lumens and working channels. This can eliminate or reduce the manual labor expended, rendering lower reprocessing costs while improving turnaround.
Cleaning - the Prerequisite for disinfecting and sterilizing surgical instruments
The reprocessing decontamination process, whether done manually or automatically in a washer-decontaminator- disinfector, can only be effective if cleaning is adequate. Effective disinfection or sterilization: (Generic Sterilization with a Pre-Vacuum Sterilizer (HI-VAC): 270-272° F (132-134° C), 16-minute exposure time, with 4 pulses and a 30-minute dry time. Generic Sterilization with a Gravity Displacement Sterilizer: 270-272° F (132-134° C), 30-minute exposure time, with a 30-minute dry time.) Sterilization of an inadequately cleaned instrument is not possible. Cleaning is the prerequisite for disinfecting and sterilizing surgical instruments.
Ultrasonic cleaners are very effective when used with hot water per manufacturer’s recommended temperature and specially formulated detergents. It is recommended that all visible debris and blood be removed from the instrument prior to ultrasonic cleaning. Contact between dissimilar metals can cause corrosion when ultrasonics is applied. Sort surgical instruments according to similar metal types to prevent corrosion. (electrolytic deposition - galvanic corrosion) It is not recommended to clean plated instruments in an ultrasonic cleaner since the ultrasonic vibration and the presence of other sharp instruments may crack or rupture the plating. Ultrasonic Cleaners do not provide the complete "proper sequence of treatments" i.e. purified final rinse(s) that are purified, purged between treatments and/or have temperatures elevated to disinfection levels. Ultrasonic cleaning can effectively remove: long term encrustation and surgical cements or glues that have dried onto instrumentation. Overloading, and low water temperature, will decrease the effectiveness of ultrasonic equipment.
Ultrasonic cleaners are effective when used with hot water per manufacturer’s recommended temperature and specially formulated detergents. It is recommended that all visible debris and blood be removed from the instrument prior to ultrasonic cleaning. Sort instruments by similar metal for subsequent processing so that electrolytic deposition (galvanic corrosion) due to contact between dissimilar metals will not occur. It is not recommended to clean plated instruments in an ultrasonic cleaner since the ultrasonic vibration and the presence of other sharp instruments may crack or rupture the plating. Always refer to the printed manufacturer recommendations prior to using ultrasonics.
John Temple
Product Development
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