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This series of self-study lessons on Central Service topics was developed by the International Association of Healthcare Central Service Materiel Management (IAHCSMM). The lessons are administered by Purdue University’s Continuing Education Division.

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Lesson Plan CRCST 109
Extended Steam Sterilization Cycles
[Reprinted from Communiqué: November/December 2009]

Many business professionals believe in the philosophy “time is money.” They emphasize the need to set priorities for completion of their many responsibilities and practice “multi-tasking” (doing several things at once). They also undertake cost-effectiveness studies to assure that plans to reduce re-work, inspections to assure compliance with quality standards, and investments in equipment to reduce labor costs can be justified.

In today’s world of healthcare, these business-related practices are also increasingly used to assure that time and the financial resources it impacts are used wisely; however, it is also true that, traditionally and today, “time is safety.” Central Service personnel cannot take shortcuts that compromise the quality of patient outcomes, and they cannot save time if doing so requires the use of practices that can endanger their customers and themselves.

Traditional standard steam sterilization cycles have effectively been used for more than three decades to sterilize utensils, power equipment, single instruments, and instrument trays, among other items. Increasingly, however, manufacturers of medical instrumentation that incorporate non-traditional complex designs and materials are providing written processing instructions that lengthen recommended sterilization and drying times.

In 1996, the U.S. Food and Drug Administration began requiring that medical device manufacturers provide specific information to CS technicians and other users of their medical devices on how to clean and disinfect or sterilize the instruments. These instructions are the source of details about requirements for extended sterilization cycles.¹ This lesson explores extended steam sterilization cycle times and their impact upon routine CS operations.

Objective 1: Review standard steam sterilization cycle times recommended by the Association for the Advancement of Medical Instrumentation (AAMI)

Standard steam sterilization cycles recommended by the Association for the Advancement of Medical Instrumentation (AAMI) have a long history of producing efficiently-processed medical instrumentation with minimal errors. The minimum cycle times for processing instruments in gravity-displacement and dynamic-air-removal steam sterilizers are shown, respectively, in Figures 1 and 2. Note: Figures 1 and 2 incorporate the normal variations in sterilizer manufacturers’ recommendations at different temperatures. CS personnel should always consult the recommendations of the manufacturers of their specific sterilizers.

The minimum cycle times shown in Figures 1 and 2 are the standard sterilization times used in healthcare facilities today, and they are recommended by AAMI; however, because many medical devices now require extended sterilization times, CS professionals are challenged to rethink and revise these traditional parameters.

Objective 2: Discuss reasons why medical device manufacturers may recommend extended steam sterilization cycle times

Extended steam sterilization cycle times result from the written recommendations of medical device manufacturers. These extended cycle times can range from up to one hour in a gravity-displacement steam sterilizer (compare that to the much lower traditional times noted in Figure 1) and up to a 20-minute exposure in a dynamic-air-removal sterilizer (in comparison to the significantly reduced time for traditional cycles in these sterilizers noted in Figure 2). Therefore, it is critical that CS technicians obtain, study and consistently follow the manufacturer’s written recommendations for medical devices being processed. Implementing a policy that these written recommendations must be provided along with all items purchased will help to ensure that those requiring extended sterilization times will be properly processed. These recommendations should be filed and used for reference and training purposes. As new medical devices are introduced into the hospital, the CS manager should receive a copy of the instructions for review.

There are several reasons why a medical device manufacturer may recommend an extended steam sterilization cycle for reprocessing specific instruments. Extended exposure times are most frequently encountered in orthopedic and neurological instrument sets that create a more significant challenge to air-removal and steam penetration. They may be heavy or dense, the devices may incorporate a complex and/or difficult-to-sterilize design, or they may contain a narrow lumen (tubular shaft) of unusual size or shape. Instrument sets, including loaner instrumentation, may have a dense metal mass that requires additional steam contact. Also, power equipment and instruments with lumens or crevices may require processing in containment devices, including rigid containers, instrument cases, cassettes, or organizing trays made of several materials, including plastic and/or metal. Note: These trays are usually multi-layered to enable users and processing personnel to remove each layer, as needed, for use and cleaning.

Requirements for extended exposure times can also be based on considerations related to a device’s country of origin. Consider, for example, prions which cause Creutzfeldt - Jakob Disease (CJD). Medical device manufacturers in Europe may recommend an extended (18-minute) pre-vacuum cycle of 274°F (134°C) to inactivate prions, and these processing recommendations do not change when devices are imported to the United States.

Figure 3 illustrates the steam sterilization cycle times required by manufacturers of some power equipment, complex instrumentation, and containers or organizers.

It is easy to see that CS managers can be confronted with significant challenges as they attempt to incorporate these types of items, each with different cycle times, into processing schedules with other items requiring traditional cycle times. Even when they effectively do so, sterilizer productivity is reduced. As the need for numerous cycle times increases, there may be a need to purchase additional sterilizers, which, in turn, can create significant financial and space constraints.

Objective 3: Explain how medical device manufacturers validate their sterilization instructions

Medical device manufacturers receive guidance about sterilization validation procedures from AAMI.⁴ Devices to be tested are inoculated with a 106 population of Geobacillus stearothermophilus bacterial spores in the most difficult-to-sterilize location in or on the device. Devices are then subjected to a half-sterilization cycle (one-half the exposure time routinely used to achieve an “overkill”). This microbiological challenge is performed for three sterilization cycles at one-half the exposure time or by developing a death-rate curve (D value). ⁵
Devices tested in sterilization qualification runs should be packaged in a manner defined by the device manufacturer that should be appropriate for the device and known by healthcare personnel. At the end of the cycle, the medical device is cultured to determine if sterilization has occurred. If it has not, exposure times must be extended until this goal is achieved.

Objective 4: Provide examples of the impact that extended steam sterilization cycle times have on the daily operation of a Central Service Department

Extended cycles may create problems for healthcare processing facilities. For example, there is insufficient research to assess the extent, if any, to which the useful and expected life of sterilization equipment is affected by extended time cycles.

Numerous other concerns become important. Manufacturers of steam sterilizers validate their equipment according to specific ANSI/AAMI guidelines, which do not cover extended cycles.⁶ Instead, sterilizer usage instructions specify standard (conventional) time and temperature cycles.
Medical devices requiring extended sterilization cycles must be processed in a dedicated load (one by themselves) to avoid damage to other medical devices being processed according to their manufacturers’ written instructions for standard exposure times. The reason: extended sterilization cycles may impact the functionality or product life of some medical devices, including some textile products, instruments with lenses, and delicate instrumentation. Newer, synthetic materials may also become warped or brittle, and coatings on some instruments may flake if they are exposed to extended processing cycles.

CS managers should not include a medical device in an extended sterilization cycle without reviewing the applicable manufacturer’s written recommendations to ensure that the device will not be damaged by extended steam exposure at the sterilization temperature used. Medical devices are typically not validated for extended cycles, so, as noted above, instruments requiring an extended cycle must be processed in dedicated sterilizer loads (often at less-than-full capacity).

Exposing sterilization packaging to steam at sterilization temperatures for an extended exposure time may break down the barrier provided by the packaging. If this occurs and the barrier qualities are reduced, the packaging material will become ineffective. While this is a potential problem, at least two packaging manufacturers have tested their products in sterilization cycles with extended exposure times of up to 30 minutes. The test results showed no significant difference in package performance cycles with standard and extended exposure times.⁷ CS managers should request test results from their packaging manufacturers, confirm that testing includes shelf life expectations, and retain this confirmation within their facility.

Other concerns relate to the biological monitoring of extended sterilization exposure cycles. The process challenge devices (PCDs) include biological indicators (BIs) that contain bacterial spores (Geobacillus stearothermophilus) that are highly resistant to the steam sterilization process. CS professionals must be concerned about what effect, if any, extended sterilization cycles have on the growth media contained within the BI. For example, extended exposure times may inactivate the growth media and yield a false negative: the biological monitor would incorrectly demonstrate negative growth and indicate the load was acceptable to release. Note: At least one manufacturer has tested self-contained BIs during extended sterilization cycles. Test results did not reveal any effect on the bacterial culture.⁸ However, it is always prudent to contact the manufacturer of the specific biological monitors that are used to assure they are safe for extended cycles.

Another concern involves the design of BIs that allows them to challenge standard sterilization cycles of only three to four minutes (depending upon temperature). A cycle with an exposure time as long as 20 minutes cannot be challenged with the same PCD.⁹

The only way that CS professionals can currently monitor extended sterilization cycles is with use of AAMI’s product testing recommendations.¹⁰ This involves the placement of BIs and chemical indicators (CIs) in locations that create the greatest sterilization challenges, such as a difficult-to-process instrument set. The quantity of BIs and CIs required will depend upon the size and configuration of the pack sample. Test devices/containers should be placed throughout the sterilizer in the locations most difficult to sterilize, and the cycle time extended to that recommended by the device manufacturer. Immediately after sterilization, the BIs should be incubated, the CIs should be examined, and the sample should also be inspected for moisture. Note: Sample contents should be discarded or reprocessed. All unacceptable test results should be studied. If the sample is dry, if all BIs are negative, and if all CIs show appropriate processing, the test has been successful. All sterilization parameters have been met, and the load contents can be released, when appropriate.

In Conclusion

AAMI Sterilization Standards Committees are currently addressing the challenges of and processing requirements for extended steam sterilization cycles. As with past changes necessitated by advancements in healthcare instrument technology, CS managers will continue to adapt processing protocols to ensure that safety concerns are always the priority consideration. They do so by keeping up with manufacturers’ written instructions during these fast-changing times and, as they do so, they make significant contributions to their healthcare team and patient safety.

Endnotes

1. U.S. Food and Drug Administration. Labeling Reusable Medical Devices for Reprocessing In Health Care Facilities: FDA Reviewer Guidance, Office of Device Evaluation. April, 1996.
2. Association for the Advancement of Medical Instrumentation. Comprehensive guide to steam sterilization and sterility assurance in health care facilities. ANSI/AAMI ST79. 2006.
3. Sue Klacik. Changing Times. Communiqué. September/October, 2005.
4. Association for the Advancement of Medical Instrumentation. Designing, testing and labeling reusable medical devices for reprocessing in health care facilities: a guide to medical device manufacturers. AAMI TIR12. 2004.
5. Details about procedures used by device manufacturers to validate sterilization recommendations are found in: Susan Klacik. It’s About Time: Extended Cycles. Healthcare Sterilization Horizons. 2008.
6. Association for the Advancement of Medical Instrumentation. Hospital Steam Sterilizers, 4th Edition. ANSI/AAMI ST8. 2001.
7. Wipack letter. Sterilization packaging products and extended steam sterilization cycles.
8. William Foltz. How Does an Extended Steam Sterilization Cycle Affect The Early Enzyme Readout Capability of the 3M Attest Rapid Readout Biological Indicators? Managing Infection Control. June, 2007.
9. See reference #4 above.
10. See Section 10 in reference #2 above

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