Steam sterilization is the most commonly used method of reprocessing surgical instruments, but some devices can't stand up to the heat or pressure of the autoclave. Electronic components require delicate handling, plastic can be compromised and lenses can fog. For these and other high-maintenance items, low-temperature sterilization bridges the gap to ensure infection prevention. Here's an overview of your non-steam options and their guiding principles.
Low-temperature sterilization options employ gaseous or chemical elements, as opposed to the autoclave's high-temperature steam exposure, in order to eliminate microbial life from surgical instruments. Besides their methods of action, the 4 main types ethylene oxide, hydrogen peroxide gas plasma, liquid chemical sterilants and ozone also differ in their most effective uses, the length of their sterilization cycles and their applicable cautions.
- Ethylene oxide (EtO) is a time-tested gas sterilization method that has been in use for more than a century, originally as a chemical weapon and agricultural pesticide before it was applied to medical instrument reprocessing. Its effectiveness in killing bacteria, spores and other microscopic matter and its ability to thoroughly penetrate interior spaces are a big reason why it's still used in hospitals' sterile processing departments today, especially on lumened and channeled instruments. Some endoscope manufacturers specify EtO only for their reprocessing.
But its cycle time can be a big drawback for facilities that demand quick turnarounds. EtO takes 2 hours or more to permeate wrapped packages and instrument channels. Then an aeration cycle of 12 hours is required to exhaust the toxic compound. Its use also necessitates the installation of a high-powered ventilation system to evacuate fumes. Some states regulate the standard to which these systems must treat the fumes, and some require facilities to obtain pesticide licenses for EtO's use.
- Hydrogen peroxide gas plasma is a widely used sterilizer because of the rapid cycles it allows. Vaporized hydrogen peroxide circulating in the sterilization chamber becomes ionized by radiofrequency energy to create a plasma reaction that eliminates the microbial colonization in wrapped packages. This can be completed in approximately 30 to 70 minutes, depending on the cycle, and doesn't require the post-cycle ventilation that EtO does.
But plasma sterilization doesn't deliver a high rate of penetration, so there are limits to the lengths and diameters of lumens that can be effectively reprocessed in the systems. Be sure to consult the instructions for use from both sterilizer and instrument manufacturers to verify which devices are most suited for hydrogen peroxide gas plasma processing.
- Liquid chemical sterilants, along with plasma sterilization, is the low-temperature option most commonly used in ambulatory surgical facilities. This is largely due to the fact that the 2 methods offer rapid-cycle sterilization: with liquid chemical immersion, in less than 30 minutes. The range of available solutions includes glutaraldehyde, orthophthaldehyde, peracetic acid, hydrogen peroxide and sodium hypochlorite. Immersion is conducted either manually or through a mechanical system.
- Ozone, the newest low-temperature sterilization option, has been marketed as the most environmentally friendly, both in its active ingredients and its by-products. The gaseous method requires only electricity, medical-grade oxygen and distilled water. An electrical charge separates the oxygen atoms to create ozone, which neutralizes microbes at the cellular level. Since the only by-products are oxygen and water, ozone sterilization does not require specialized ventilation or exhaust systems.
At 4-and-a-half-hours, however, ozone's sterilization cycle isn't as rapid as those of hydrogen peroxide gas plasma or liquid chemical immersion, which may limit its usefulness in the eyes of efficiency-driven outpatient surgery facilities. Ozone hasn't yet been widely implemented in central sterile departments across the U.S., though it has gained some popularity overseas.
When to go low
Advances in technology and materials have made some of the instruments that once couldn't withstand the autoclave heat- and moisture-resistant. For example, some rigid scopes and cameras that once required low-temperature soaks can now be successfully steam sterilized.
Even so, some manufacturers suggest and some sterile processing techs prefer low-temperature methods, as they seem to subject the instruments to less wear and tear and may extend their usable life spans. A common reprocessing misstep that's best to be avoided, however, is wrongly assuming that just any instrument can be effectively sterilized through low-temperature methods.
The questions of whether low temperatures are warranted, and which method is validated, for a particular instrument, are guided primarily by the device's specifications. For low-temperature sterilization, evidence-based practices originate from instrument and sterilizer manufacturers' instructions for use.
A set of guidelines on chemical sterilization and high-level disinfection in healthcare facilities, published by the American National Standards Institute and Association for the Advancement of Medical Instrumentation and revised last year also defines the options and selection criteria. According to ANSI-AAMI's ST-58 guidelines (tinyurl.com/p5nnqnv), ascertaining and evaluating a medical device's proper method of reprocessing should be a part of its trialing and purchasing process.
Compliance and caution
It's critical to make sure that each method is conducted correctly and operated effectively. A large part of this is incumbent upon central sterile technicians following the rules and monitoring the process for compliance. Instruments must be thoroughly cleaned and decontaminated in order to be effectively sterilized, for instance. For gaseous methods, instruments must be wrapped or packaged in accordance with the sterilizer's directions. The chamber must be loaded properly, and not overloaded.
Use a biological indicator at least once a day to determine if the sterilization method is effective. Many mechanical sterilization devices also have fail-safe tests built in. For example, instrument packages processed in hydrogen peroxide gas plasma systems must be dry. If moisture is detected during the cycle, it will abort.
Lastly, reprocessing techs must be competent not only in the proper use of sterilization equipment and products, but also in the safe handling of their potential hazards. Manufacturers' safety data sheets provide recommended practices for avoiding skin and respiratory contact with their volatile chemicals, for monitoring the air for toxic fumes and for developing contingency plans to prepare staff for cleaning up a spill or responding to a leak.