The 3M Healthcare Tech Line for Sterilization fields questions from customers across the country. Here are some of the questions we hear frequently:
Q: What is the appropriate way to load peel pouches in the sterilizer?
ANSI/AAMI ST79:2010, Section 8.5.1 General considerations, states:
"Load configurations should ensure adequate air removal, penetration of steam into each package, and steam evacuation." "In loading any sterilizer, the sterilizer manufacturer's written instructions should be followed…."
ANSI/AAMI ST79:2010, Section 8.5.2 Paper-plastic pouches, states:
"Paper-plastic pouches should stand on edge in relation to the cart or shelf, with the paper side of one pouch next to the plastic side of the next pouch; holding racks or baskets specifically designed for pouches can be used."
"Rationale: Special racks or baskets facilitate placing paper-plastic pouches on edge and properly spaced in the sterilizer for adequate sterilant contact and drying. They are also helpful in keeping similar small packages in position during the sterilization process."
What is this new IUSS term I’m hearing?
In an initiative to harmonize guidance around the practice of “flash” sterilization, AAMI and several other organizations met and developed a multi-society position statement which has now been endorsed by seven organizations. The position statement explains that “flash sterilization” is an outdated term and recommends the use of a new term, “immediate-use steam sterilization” to better reflect
the variety of steam sterilization cycles now used to process items not intended to be stored for later use
Read the full Immediate-Use Steam Sterilization statement at http://www.aami.org/publications/standards/ST79_Immediate_Use_Statement.pdf
Low Temperature Sterilization
Is it true that transferring ethylene oxide sterilized loads to an aeration cabinet is no longer acceptable?
Yes, if the Instructions for Use supplied with the ethylene oxide containers used at your facility specify the use of a single chamber process, then transferring loads to a separate aeration cabinet is no longer an acceptable practice.
In 2008, the EPA completed a Reregistration Eligibility Decision (RED) for Ethylene Oxide (EO). The EPA determined that the benefits of using ethylene oxide as a pesticide outweigh the associated risks, provided that risk mitigation measures are adopted by users and that suppliers amend EO labels to incorporate the recommended risk mitigation measures. The EPA required suppliers to add two specific restrictions for EO usage in hospitals and healthcare facilities to their labeling:
EO sterilization must be performed in vacuum or gas tight chambers designed for use with ethylene oxide
A single chamber process is required for EO treatment (i.e. sterilization and aeration are to occur in the same chamber).
Click this link
to read a tutorial explaining the EPA RED for EO in more detail.
Sterilization Monitoring Tools
Class 5 vs. Class 6 Cls – What is the difference?
What are the differences between Class 5 and Class 6 CIs?
Class 5 Chemical Integrators react to the three critical variables of a steam sterilization cycle (time, temperature, and the presence of steam). In addition, their performance is required to correlate to that of a biological indicator (BI). As a result, Class 5 integrator results are similar to those of a BI and Class 5 CIs can detect failures where the selected temperature isn’t reached. This failure condition is likely to occur when there is incorrect packaging and loading, air/steam mixtures, or the wrong cycle is run.
In contrast, Class 6 CIs react to the three critical variables for a specified cycle, and their performance may or may not correlate to a BI. Class 6 CIs are cycle specific, i.e. they should only be used in the specific cycle for which they are labeled. It is important to realize that if you run multiple exposure times and temperatures, you must use a distinct Class 6 CI to monitor each cycle time and temperature. And, because Class 6 CIs are not required to correlate to a BI, a Class 6 indicator could reveal a pass where a BI would indicate a failure.
To learn more about the ability of Class 5 CIs, Class 6 CIs, and biological indicators to detect defined failure conditions in steam sterilization cycles click on the links below.
Air-Leak Detection Capability of Various Steam Sterilization Indicators
Sterilization Indicator Detection of Temperature Differences in Steam Sterilization Cycles
Are Class 6 Chemical Indicators (CIs) better than Class 5 Chemical Integrators?
No. ANSI/AAMI/ISO 11140 describes 6 classes of CIs that are classified according to their intended use and performance requirements (see table below). It is important to keep in mind that these classifications are NOT ranked in order of importance or performance.
Class 1: Process Indicators
For use on the exterior of individual packs, peel pouches, containers,
etc… to indicate exposure to the sterilization process
Class 2: Indicators for Specific Tests
For use in specific test procedures (i.e. Bowie-Dick Type Test)
Class 4: Multi-Variable Indicators
For use inside individual packs, peel pouches, containers, etc…
Reacts to two or more of the critical variables of the sterilization process
Class 5: Integrating Indicators
For use inside individual packs, peel pouches, containers, etc… Reacts
to all critical variables of the sterilization process and the Stated Values
must be equivalent to or exceed BI performance requirements
Class 6: Emulating Indicators
For use inside individual packs, peel pouches, containers, etc… Reacts
to all critical variables of the sterilization process, with the Stated
Values having been generated for a specific sterilization process
Our steam sterilizer aborted half-way through the cycle and we incubated
the BI expecting the results to be positive, but the BI was negative. Is this a problem?
No. The fact is, you should be reassured when the spores in a BI are killed.
That’s because the population of spores in a BI provides a challenge greater
than that encountered in a normal load. Hospital steam sterilization processes are
based on the half cycle overkill method where the time required to kill the BIs is
determined, then doubled to establish the final cycle exposure time.
So the final exposure time provides a safety factor.
As you will learn in the attached article by Dr. Sailaja Chandrapati, monitoring the
sterilization process is not simply about measuring the cycle exposure time – it’s about
measuring the ability to deliver sufficient lethality to kill the highly-resistant organisms
within the BI. To learn more,
read the full article.
I have heard that 3M™ Attest™ Rapid Readout Biological Indicator Test Packs should not be
used to monitor extended steam sterilization cycles. Is this true?
No. The Instructions for Use for the 3M™ Attest™ 41382 Rapid 5 Steam-Plus
Test Pack includes the following Indications for Use statement:
121°C (250°F) gravity displacement steam sterilization cycles ≥30 minutes.
132°C (270°F) dynamic-air-removal steam sterilization cycles ≥4 minutes.
A minimum cycle time is listed but a maximum cycle time is not specified. All biological indicator (BI)
test packs on the market today are designed to be equivalent to the AAMI 16-towel test pack and have similar
indications for use in their product package inserts.
AAMI has a PCD Working Group comprised of representatives from device manufacturers, FDA, and end-users who are working to address the issue of monitoring extended steam sterilization cycles.
Does 3M have data showing that 3M™ Attest™ Rapid Readout Biological Indicators are able to withstand exposure to extended steam
sterilization cycles and still perform properly to detect cycle failures?
Yes. In response to the increased usage of extended steam sterilization cycle times in health care facilities, 3M completed
a study with 3M™ Attest™ 1292 Rapid Readout Biological Indicators (BIs) that demonstrated that the ampoulized media in the BIs
functions properly after exposure to extended cycle conditions
Note: The 3M™ Attest™ Rapid 5 Steam-Plus Test Pack contains the 3M™ Attest™ 1292 Rapid Readout Biological Indicator.
Attached please find the white paper titled "Effect of Extended Steam Sterilization Cycles on Self Contained Biological
Indicators with Enzyme-based Early Readout" (PDF, 31.1 KB) by William Foltz. The white paper provides a summary of the study protocol,
methodology, and results and concludes that the BI performance was not affected by exposure of the ampoulized media to extended cycle
conditions (134ºC for 20 minutes).
Sterilization Quality Assurance
Did anything change related to monitoring and releasing implants with the publication of AAMI ST79:2010?
AAMI ST79:2010 continues to recommend that implant loads be monitored with a biological indicator (BI) process
challenge device (PCD) that also contains a Class 5 integrating indicator, and that the load should be quarantined
until the BI results are known. In section 10.6.1 Process monitoring devices, of AAMI ST79:2010 it states:
“Every sterilization load containing implants should be monitored with a PCD containing a BI (a BI challenge test pack).
A Class 5 integrating CI should be included in this PCD. Implants should be quarantined until the results of the BI testing are available
Recommendations for early release of an implant, before the BI result is known, also have not changed in AAMI ST79:2010. If it is not possible
to quarantine the implant until the biological indicator is negative, because of a documented medical emergency, then the implant can
be prematurely released on the result of the Class 5 integrating indicator in the BI PCD provided that all the other monitoring results
were acceptable. Two forms are still provided in Annex L of ST79:2010 – an implantable devices load record to document all
implant loads and an exception form to document premature release of implants before the BI results are known.
What is new in AAMI ST79:2010 is that guidance on the use and applications for Class 6 emulating indicators is now
provided. With respect to implant loads, a Class 6 emulating indicator, within a PCD, can be used as an additional
monitoring tool (in the cycle for which it is labeled).
It is important to point out that, according to AAMI ST79:2010, a Class 6 PCD cannot be used in the place of a BI PCD to release
implants and a Class 6 emulating indicator cannot be used to release implants in an emergency.
When the OR runs a BI in a flash sterilizer, do they need to incubate a new control?
As referenced in ANSI/AAMI ST79, Section 10.7.2.3 and 10.7.4.3 Test procedure:
Each day that a test (i.e. processed) BI is incubated, at least one non-processed BI should also be incubated as
a positive control in each incubator. Write a "C" [for "control"] and a date on the BI label. The positive
control should be from the same manufacturing date and lot number as the processed BI. Incubate the
positive control for a visual color change. The test BI results are not valid until the control BI gives the
expected positive result.
Use of a daily positive control BI helps ensure:
- correct incubation temperatures are met;
- viability of spores have not been altered due to improper storage temperature, humidity, or proximity to chemicals; and
- capability of media to promote growth
How many CIs should be placed inside multi-layered trays?
AORN:2011, Recommended Practices for Selection and Use of Packaging Systems for Sterilization, Recommendation IX –
A chemical indicator/integrator should be placed inside each package and an external chemical indicator affixed outside
each package to be processed, states:
"5. Two chemical indicators/integrators should be placed inside rigid containers, one in each of two opposite corners
of the inside basket. Multi-level containers should have a chemical indicator/integrator placed in two opposite
corners (e.g., one in each of two corners) of each level.”
"6. A chemical indicator/integrator should be placed on each level of multi-level wrapped sets."
ANSI/AAMI ST79:2010, Section 10.5.2.2.2 Internal chemical indicators, states:
"…The CI should be placed in that area of the package, tray, or container device (rigid sterilization container system,
instrument case, cassette, or organizing tray) considered least accessible to steam penetration; for a containment device,
the manufacturer’s written instructions for placement of the CI should be consulted. This location might or might not be the center of
the package, tray, or container system…"
FAQ: Applications and Limitations of Parametric Release
What is parametric release?
Parametric release is a concept for release of sterilized product loads that is based on measurement of physical process
parameters i.e., time, temperature, pressure readouts, rather than information from chemical and/or biological indicators.
Does the concept of parametric release apply to all types of sterilization processes?
Yes. Parametric release can theoretically be applied to all terminal sterilization processes.
However, parametric release is most often used for steam and radiation sterilization processes.
Is parametric release a new concept?
No. Parametric release has been used by Medical Device and Pharmaceutical manufacturers for many years.
Where are the requirements for parametric release listed?
The requirements to achieve parametric release are defined in various international sterilization standards.
Relative to steam sterilization, the most pertinent standard is ISO 17665-1: 2006 Sterilization of health care
products – Moist heat – Part 1: Requirements for the development, validation and routine control of a sterilization
process for medical devices.
If parametric release is standards driven, why hasn’t AAMI adopted this standard for application in the United States?
The 17665-1: 2006 standard has been adopted by the AAMI organization as ANSI/AAMI/ISO 17665-1: 2006, however,
it is considered applicable only for Medical Device and Pharmaceutical manufacturers. AAMI’s philosophy, as
determined by its membership including hospital practitioners, medical device manufacturers and regulatory personnel,
is that this standard is not appropriate for use in health care facilities based on the document’s requirements for
technical expertise, and physical and financial resources. The standard recommended by AAMI for steam sterilization
assurance in health care facilities is ANSI/AAMI ST79: 2010 Comprehensive guide to steam sterilization and sterility
assurance in health care facilities. The ST79 document does not require validation of the sterilization process but
does require implementation of a quality system and routine monitoring with physical, chemical and
Why is parametric release applicable for Medical Device and Pharmaceutical manufacturers but not health care facilities?
Standards such as ANSI/AAMI/ISO 17665-1 for steam sterilization require that the sterilization process be validated. The sterilization
process is defined as all activites required to process an instrument, including cleaning, packaging, sterilization, and storage.
Validation requires a high level of repetitive testing to define and document the capability of the sterilization process for the product
being sterilized. Validation of the sterilization process includes:
- Verification of sterilizer operation and separate systems for sterilizer control and monitoring
- Verification of steam quality
- Control and monitoring of instrument of all cleaning processes
- Standardized packaging
- Standardization and testing of ALL loading configurations
- Standardized cycles for each loading configuration
- Defined and validated procedures for sterilizer unloading, item transfer and storage
- A detailed change control system, which drives re-validation when any changes are made
to the devices, packaging, or process.
Additionally, to ensure that all operations in the sterilization process are conducted the same each and every time, a detailed
quality system such as outlined in the ISO 13485 standard must be implemented and functional in all areas where reprocessing
Do health care facilities in Europe utilize parametric release for sterilized items?
Yes, in some areas of northern Europe , although the actual number or percentage of hospitals using parametric release as specified
in ISO 17665-1: 2006 is unknown; the number is believed to be small. European countries that are members of the European Union are
obligated by law to follow European standards for sterilization. As the ISO sterilization standards are now adopted by Europe,
hospitals in most European countries are obligated to follow appropriate sterilization standards such as ISO 17665-1. It is
questionable, however, as to whether or not health care facilities truly have the capabilities and resources to comply with the
requirements of the 17665-1 standard.
What is the prediction for the future of parametric release in health care facilities in the United States?
Due to the high cost, other resources (which are significant) and load consistency requirements needed to achieve
validation and implement parametric release, it is unlikely that this method of sterilized items release will become
a reality in U.S. health care facilities in the foreseeable future.
How many years should sterilization records be kept?
ANSI/AAMI ST79:2010, Section 10.3.2 Sterilizer records, states:
"The length of time that records must be retained varies throughout the country.
Each health care facility is responsible for determining its record- retention policy on the basis of state
and local regulations, legal considerations (e.g., statutes of limitation for lawsuits), and its individual
situation. Sterilization records should be retained according to the policy and procedure established by the
individual health care facility."