Evolution of sterilization technologies

Cynthia Hubbard, RN, BS

Opportunity

Opportunity: a favorable juncture of circumstances; a good chance for advancement or progress (©2010 Merriam-Webster, Incorporated).

Happy New Year! It’s a fresh start … with unlimited possibilities. We had a fast-paced December and are ready for what may be next on the scene. Advances in science leading to new technology are frequently in the news this time of year. There is no doubt that technology advances have made our lives easier. Some of my personal lifetime technology application favorites include the dishwasher, clothes dryer, computer and automobile. I could go back to the manual versions of these 20th Century tools, if necessary, but it’s the convenience I would miss. I wonder what’s coming on board this year to bring even more convenience to my life. And, more importantly, will I be open and ready to embrace progress to make it a favorable juncture of circumstances?

This thought leads me to discuss questions related to newer sterilization technologies, and new applications of existing technologies to address process outcomes in cleaning and sterility maintenance. During the 1980s a search for the ideal sterilant and high level disinfectant (HLD) was conducted in earnest to address the issues of the day: cost effectiveness; environmental friendliness; fast instrument turnaround; minimal toxicity to the user and our patients; and flexibility in product use.¹ Since these economic drivers of over 25 years ago are still the focus in 2011, let’s start with a short recap of sterilization technologies that have evolved to address environmental, safety and time concerns.

Q. What are examples of oxidizing chemicals most recently applied to low temperature sterilization and HLD technology?

A. The oxidizing properties of hydrogen peroxide and ozone have been developed for use in healthcare applications. Hydrogen peroxide (H₂O₂) vapor and gas plasma was approved for use by the FDA in 1993 with the STERRAD® low-temperature sterilization system. The newest model, the STERRAD® 100NX™, was approved by the FDA in 2007.¹ It accomplishes sterilization of single-channel flexible endoscopes in 38 minutes.²

Hydrogen peroxide (H₂O₂) vapor in a low temperature sterilization system is also used in the Amsco® V-Pro™ 1 Plus. This device acquired FDA clearances in 2007 and 2009. Liquid H₂O₂ solution is contained in a disposable cartridge with enough sterilant for 30 cycles. After completion of either a 28 minute or 55 minute cycle the sterilized medical devices (including endoscopes) can be used immediately or stored for later use.¹

Ozone in gaseous form has been used as a sanitizer or sterilant for many years in industrial applications such as water purification or improving the air quality of a food processing unit, dairy or a bakery. But in 2003 a device was approved by the FDA for use in healthcare applications.¹ TSO₃’s Sterizone® 125L (formerly named 125L Ozone Sterilizer) is a low-temperature, high-capacity, general purpose sterilizer which uses only oxygen, water and electricity to generate ozone as the sterilant for heat and moisture-sensitive instruments.²

Q. Is there an easy technology application to help us determine when freshly steam-sterilized packs are safe to touch and move from the sterilizer cart?

A. A low-cost application of infrared technology is being used by some CS departments to take the subjectivity and guesswork out of determining when sterilized packs are cooled enough to touch safely. A hand-held, battery powered, non-contact infrared digital thermometer lets a technician know the temperature of a sterilized pack without handling it. This portable device can also hold and store temperature data in either ºC or ºF, if you wish. When the temperature of the wrapped package or instrument set is cool it can be transferred to storage or released to the user with confidence that you are not contaminating it.

The Association for the Advancement of Medical Instrumentation’s Comprehensive guide to steam sterilization and sterility assurance in health care facilities ST79:2010 has been published and is now available for us to consult for additional insights into best practice in determining cooling time. “Seasonal and geographic variations in ambient temperature and humidity affect cooling time, as do other factors unique to the individual facility. The type of sterilizer used can also affect cooling time, depending on how hot items are when they leave the sterilizer. Consequently, the time allowed for cooling has to be based on professional judgment and experience.”³

What temperature do you think represents cool? Although ANSI/AAMI ST79:2010 does not define cool with a specific temperature, I suggest that using its recommended room temperature range as a benchmark can be a starting point to discuss and define your department’s standard for cool. ANSI/AAMI ST79:2010 recommends that the “temperature in general CS work areas be between 68–73ºF with relative humidity between 30-60%; sterile storage temperature may be up to 75ºF with 70% relative humidity.” “Although a minimum cooling time of 30 minutes is recommended, adequate cooling could require 2 hours or more.“³

Packages sterilized within a high moisture environment retain water in the form of a gas or water vapor following the drying cycle until they are sufficiently cool. ANSI/AAMI ST79:2010 reinforces that “packages should not be touched until they are cool because a hand can act as a point of condensation for the warm water vapor emanating from the package, thereby creating a moist area on the outside of the package. This moist area can act as a wick to draw bacteria from the hands into the package. Placing the sterilizer cart in a low-traffic area reduces exposure of the items to particles settling from the environment and minimizes the possibility of inadvertent personnel contact with the sterilized items when they are especially vulnerable to contamination. Placing a warm pack on a cool surface could cause condensate to form, resulting in contamination of the pack.”³

Q. Would a minimum of 30 minutes cooling time also apply to sterilization containers? I thought that the pressure of handling a container would not contaminate its contents?

A. The issue with rigid sterilization container systems is the potential for re-condensation of steam vapor that can occur if they are handled while hot. ANSI/AAMI ST79:2010 states that “because the materials used for containers are not absorbent, condensate can appear as small droplets on or within the container system. Condensate within any container system can compromise the sterility of the contents if the condensate is able to come into contact with outside contaminants. The potential for outside contamination depends on several factors, such as the type of filter media and the seal of the filter or valve. The potential for contamination also depends on the construction of the container system, e.g., whether the container system has a solid bottom or feet to raise it above contaminated surfaces.”³ Because the metals used in rigid sterilization containers can cause burns when they are hot, wait to handle them until they are cool. Using the non-contact infrared digital thermometer lets a technician know the temperature of a container before handling it. Again, it is up to your department to follow the ANSI/AAMI recommendation to use professional judgment in establishing temperature standards for defining cool.

Q. Why have we been asked to monitor the mechanical washers with a soil test?

A. For years we have been saying that if a medical device is not clean it can not be sterilized. Over the past decade technology has been applied to making a disposable, inexpensive, yet effective, soil test to check the cleaning outcomes of mechanical washing equipment. Washing equipment can be programmed with many different types of cycles and must be properly cleaned and maintained to work effectively. Additionally, there are many variables (e.g., enzymatic pre-soak, ultrasonic cleaning, loading of the washer, cycle time, cleaning chemistry, water quality, etc.) in an effective decontamination process.

IAHCSMM’s Central Service Technical Manual clarifies the use of a soil test in this way, “A commercial monitoring product is available that mimics dried blood, and tests the effectiveness of automated washers. It is designed to parallel worse case scenarios of instruments processed in mechanical cleaning equipment, and to monitor the machine’s ability to remove bioburden. After the cycle has completed, the monitor is inspected for residual bioburden. If any residue is present, there is a clear indication that some parameters needed for cleaning are not being achieved. Failure of this quality assurance check can alert one about the need to investigate each variable, and it can also assist in identifying and resolving the problem.”⁴

There are several commercial soil test products on the market and I suggest that you research options to pick the one that is best for your practice. Consult ANSI/AAMI ST79:2010 for guidelines (Section 7 and Annex D).

When it comes to determining policy for frequency of soil testing, follow the ANSI/AAMI ST79:2010 recommendations that “mechanical cleaning equipment should be tested upon installation, weekly (preferably daily) during routine use, and after major repairs.”³ A major repair is defined as “outside the scope of routine preventive maintenance and that significantly affects the performance of the equipment. Examples include replacement of the water pump(s), detergent delivery system, heating system, water delivery system, water treatment system, or computer control or an upgrade to software.”³

Summary

Technology applications will continue to evolve for our benefit in sterile processing. During this month when we launch 2011’s activities, I hope that you have optimism for all that you and your team can accomplish this year to advance progress in your department. I further hope you will recognize and embrace opportunities that will come your way. Your positive energy is needed and will greatly influence those around you in the coming year. And, may you walk gently through your day and enjoy many moments of satisfaction in the contributions you make to safe patient care.

References

1. Schneider PM. New Technologies in Sterilization and Disinfection. Disinfection, Sterilization and Antisepsis: Principles, Practices, Current Issues, New Research, and New Technologies 2010 Ed.
2. Williamson, JE. Next-gen washers and sterilizers get leaner, greener, yet more feature-rich. Healthcare Purchasing News. 12/08.
3. Association for the Advancement of Medical Instrumentation. Comprehensive guide to steam sterilization and sterility assurance in health care facilities. ANSI/AAMI ST79:2010. Section 3 (Design considerations); Section 7 (Cleaning); Section 8 (Packaging, preparation, and sterilization) and Annex D (User verification of cleaning processes).
4. IAHCSMM. 7th Edition Central Service Technical Manual. P 152.

Cynthia Hubbard, RN, BS, is an independent nurse consultant and published author of articles related to best practices in sterile processing. Contact Ms. Hubbard at cynthiahubb@gmail.com.