Steam quality is a measurement of the amount of moisture in steam. For steam sterilization, there is typically greater than 95 percent steam and less than 5 percent moisture. Steam purity is a measure of the amount of contaminants in steam usually coming from the boiler. Impurities in the steam source may have an adverse effect on patients, equipment and the sterilizer itself. Various contaminants may find their way into the steam source. As well as being an obvious risk to patients, these reactive contaminants in the steam may have a damaging effect on the materials in the load, may cause corrosion and impair the longevity and functionality of the devices to be sterilized. Reactions may occur when contaminants come into contact with the surgical devices either directly or indirectly with materials that will come into contact with the sterilized product.
Recently, AMMI published TIR34:2007, which defines four levels of water quality and in what way reprocessing personnel and water maintenance personnel should collaborate with administrative personnel to implement the water quality initiatives:
Step 1: Assessment of water quality: The potable water from public utilities should be analyzed by water maintenance personnel to determine whether the water requires treatment and if so what kind of treatment.
Step 2: Implementation of water treatment process: Water maintenance personnel with device reprocessing personnel should ensure that water treatment provides the type of water quality needed for medical device reprocessing.
Step 3: Assurance of proper water quality: Water quality for the various stages in medical device reprocessing should be audited so that the proper water quality is used in each area.
Step 4: Ongoing monitoring of water quality: Where applicable, monitoring procedures should be established to ensure that the treated water is of adequate quality for reprocessing.
TIR34:2007 identifies four categories of water quality, which is determined by the medical device to be cleaned and by the disinfection or sterilization process used. Portable water can be used for pre-cleaning and cleaning of critical devices and for rinsing of semi-critical and non-critical devices. High-purity water is required for critical medical devices and recommended for semi-critical devices as well. Portable water is water that comes from the tap and requires no further treatment provided that it meets the characteristics in Table 2.
Surgical instrument cleaning needs high-purity, low-endotoxin water. Conductivity measures total dissolved solids. Elevated dissolved solids can cause “mineral tastes” in drinking water. In addition, water high in dissolved solids can cause problems with industrial equipment, automated washers and boilers. According to the literature, conductivity of the water used for surgical instrument cleaning should be limited to 10uS/cm to a maximum of 30uS/cm. This can be achieved easily with an reverse osmosis system. For example, even though our tap water in New Jersey has a conductivity level of 500 to start, which is extremely high, after using a relatively inexpensive reverse osmosis system the conductively level of tap water can be greatly reduced to below the recommended values.
Water containing calcium or magnesium can form hard water deposits. These deposits become less soluble as temperature increases and can trap spores on instrument surfaces, which can survive steam or gas penetration. Soft water treatment replaces these elements by sodium ion exchange. However, softened water has no effect on conductivity without partial ionic reduction that is why reverse osmosis water treatment is important for surgical instrument cleaning preparation. A defective softener has sodium chloride and resin used in the process, which may be part of the back wash process. Chloride is present in most feed waters. Removal of chloride treated water can be read by a conductivity meter coupled with an automatic dump valve drain; where the feed water is above 120 milligrams per liter ion exchange or reverse osmosis is required. Silica (silicate) is also not removed with water softeners. Reverse osmosis or deionized water is required.
Water softening systems have little control over water purity and downstream protection from chloride corrosion of the hospital washer and surgical instruments. AAMI TIR34:2007 states, “Softened water is water that receives limited treatment (softening) to remove inorganic material from the water. It will not reduce microbial levels, nor will it remove organic material from the water.”
According to TIR34:2007, reverse osmosis has become widely used in medical device water purification systems. The advantage of reverse osmosis water is that it “filters out contaminants to a high of efficiency. Reverse osmosis removes particulate matter, organic molecules and pyrogens that deionized water cannot. It is less corrosive to steel and copper.” It is cheaper to run and maintain than deionized water systems. HTM2030 suggests that reverse osmosis would be the obvious choice as a core treatment technology, given its excellent impurity removal spectrum across ionic, organic and microbiological species.
The numbers, types and species of microorganisms in a water supply and in used cleaning supplies increases every time the cleaning products are re-used. Good housekeeping procedures need to be followed to contain and confine organisms to prevent contamination. The Association for the Advancement of Medical Instrumentation (AAMI) and the Association of periOperative Registered Nurses (AORN) recommend using de-mineralized water in the final cleaning step.
There is special concern when ophthalmic instruments are re-processed. Toxic anterior segment syndrome (TASS) is an acute inflammation of the anterior chamber of the eye following cataract surgery. It has been linked to irritants on the surfaces of intraocular surgical instruments, from detergent residues and from bacilli in water baths of ultrasonic cleaners. For example, potable or softened water in early processing steps may result in unacceptable endotoxin levels. In fact, TIR34:2007 recommends that high purity water be used for the final rinse when re-processing medical devices that contact the blood stream, cerebral-spinal fluid or the anterior chamber of the eye.
Although the AAMI working group found insufficient evidence for using high-purity water for instrument processing for every stage of the decontamination process, using purified water has its advantages. Some healthcare facilities have installed central water treatment facilities for various departments in the hospital. Others have found a cost effective way to install point of use water treatment units in the reprocessing area.
Healthcare professionals as well as the public recognize the importance of water as a universal solvent. Hard water ions and chlorides can affect the outcome of instruments processed in healthcare settings. It is important to understand the importance of water in the cleaning process. Water is required to thoroughly rinse off organic and inorganic contaminants and to remove chemicals including detergent residue from medical devices. In conclusion, each healthcare facility needs to determine how pure their water is and to regularly monitor water quality and steam quality, and take the necessary steps, if required, to obtain greater water purity when processing surgical devices and patient-care items.