Sterilization Unwrapped

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Sterilization Unwrapped

By Becki Harter, CST, CRCST

Sterilization's No. 1 enemy is biofilm, seen here in a CDC scanning electron photograph of Staphylococcus by Janice Carr of the Centers for Disease Control and Prevention (CDC). A distinguishing characteristic of biofilms is the presence of extracellular polymeric substances, primarily polysaccharides, surrounding and encasing the cells.

Since the 1950s when sterilization technology was in its beginning stages, sterilization processes and methods have changed considerably. The concept of steam and dry heat sterilization, which had its beginning in the 1880s with work done by Pasteur and Koch, has developed into the more sophisticated and technological development of monitoring sterility assurance we have today. At one time medical devices were considered sterile if they had undergone a sterilization process. If all gauges and pressures read correctly and the sterilization equipment functioned properly, medical devices were considered sterile.

Since the dawn of sterilization processes, incorporation of techniques to monitor and measure the resistance of microorganisms and the efficacy of the sterilization process continue to grow and become more and more sophisticated. Where steam and dry heat were the only available sterilization methods in years past, new challenges appear on the scene with the additional sterilization methods available today. Use of sterilization parameters that incorporate physical/chemical and mathematical procedures to determine the sterilization process parameters and use of biological and chemical indicators to measure SAL (sterility assurance) have contributed to a better understanding and the safety and effectiveness of the sterilization process. Sterile is no longer sterile unless there is test data to support that claim.

Organizations such as the Food and Drug Administration (FDA), Association for the Advancement of Medical Instrumentation (AAMI) and the International Association of Healthcare Central Service Material Management (IAHCSMM) have been prompted to write standards and develop protocol for sterilization processes, that has played an integral role in the safety and effectiveness of medical devices used in healthcare today.

Sterilization processes available today

1. Steam: wrapped or unwrapped medical devices
Gravity displacement
Dynamic air removal (pre-vac)
Dry heat (least used and least understood)
Convection heat

2. EO/ETO: Ethylene Oxide
Plasma: Hydrogen peroxide plasma or gas plasma
PAA: Peracetic Acid

Each method of sterilization used in respect to a medical device must be validated and tested in a laboratory setting to determine its safety and effectiveness for use in a healthcare setting. The validation process has been developed using the published standard healthcare cycles for each sterilization process. Validation of a medical device in a sterilization process requires the following elements:

  • SAL (sterility assurance level) 10 to the minus sixth power (one part per million) kill in half of a published healthcare standard cycle
  • Use of the worse-case scenario for a particular medical device (worst contamination and configuration)
  • Contamination of the medical device with a microorganism specific to the sterilization method tested (steam: Bacillus Stearother-mophilus)
  • Placement of biological indicators specific to sterilization process in areas of greatest challenge to the sterilization process (middle, sides, corners or hard-to-reach areas in the medical device(s))
  • Use of a sterilization process according to its respective parameters for temperature, duration in a half cycle or its chemical composition/concentration ratio.
  • Growth of microorganism post-sterilization cycle to determine SAL was met

If SAL was met in a half cycle, the device can then be assured of its safety and effectiveness in a published standard healthcare cycle. Chemical sterilization processes do not have half cycles. Sterility assurance level must be reached in a full cycle only.

Some Problems Seen in Healthcare

Validation and test methodology have been developed using published standard healthcare cycles. What that means is that the FDA and the AAMI have developed testing protocol to mirror the tested, validated and published sterilization processes used in healthcare today. The published standard healthcare cycles seen today are supported by test data specific to the sterilization process, device and the respective microorganisms that present the greatest challenge to that process. Sterility assurance levels of 10 to the minus sixth (one part per million), is the level of microorganism colony growth that would be considered not harmful to humans or able to produce disease.

Q. What happens if a healthcare device manufacturer (HDM) does not adhere to the published standard healthcare cycles?

A. Patient safety is compromised. There are some HDMs that do not routinely adhere to the published standard healthcare sterilization cycles. Manufacturers of orthopedic and neurological medical devices are two types of HDMs that do not routinely adhere to the standard published healthcare cycles. It is not uncommon to find cycle parameters of greater than 8 to 45 minutes sterilize and 60 minutes dry times at 270, 275 or 250 degrees.

Q. Should the healthcare facility ask for instructions for use?

A. Yes. Instructions for use must be kept on file in infection control and in the central processing department (CPD). Instructions for use include:

  • Cleaning/disinfection directions
  • Processing/sterilization directions
  • Adverse reaction/care recommendations

Should healthcare facilities have a summary of the validation/test methodology of all medical devices or systems used?

Yes. The summary will tell you:

Which sterilization method was used

  • Half cycle used
  • Organism used
  • SAL achieved
  • Wrapped cycle (dry time)
  • Unwrapped cycle (no dry time)

Steam cycles that are listed for medical devices from the HDM that do not have dry times listed are more often than not for unwrapped cycles only.

Q. Does it matter if the test methodology was done only for unwrapped cycles only?

A. Yes. If a medical device is sterilized in a wrapped cycle utilizing data compiled for an unwrapped cycle, patient safety has been compromised and an infection control risk created. If the HDM has validated for unwrapped cycles only, the medical device can be sterilized in an unwrapped cycle only until the HDM does testing in a wrapped cycle. Wrapped cycles create an additional challenge to the sterilization process and must be tested/validated separately for SAL.

Q. Should the healthcare facility ask if the cycles are for wrapped? Unwrapped cycles?

A. Yes. This information can also be seen in the validation/test methodology summary. If there is any doubt, ask. Patient safety is the No. 1 concern.

Q. What does a healthcare facility need to do if a HDM does not have the information and published standard cycle parameters?

A. Do not use the medical device. Other things that can be done include:

  • Working with the HDM to get the required information or sterilization cycle
  • Healthcare facility validating medical device in the standard published healthcare cycle (recommended by some HDM but this practice is not widely accepted by healthcare nor FDA)
  • Using an alternate HDM that has the appropriate approval/validation and is comparable to the original device.
  • Reporting to the FDA via Med Watch any HDM that does not have appropriate standard published healthcare cycles and or validation/test methodology or approval for use in a healthcare setting.
  • Using medical devices that have all the appropriate information, validation and approvals from the FDA.
  • Searching the FDA Web site ( for approvals and use of medical devices.
  • Setting up in healthcare facility policies and procedures that support use of approved medical devices with sterilization methods consistent with what is available in healthcare. Departments to include in these discussions are: CPD/SPD, medical director, administration, infection control, risk management, surgery director/manager, OR staff and purchasing.
  • Getting involved with local and national healthcare standards organizations to stay abreast of new innovations and changes in healthcare medical device management.

Investigating every medical device or system prior to trial, consignment, purchase or use.

Q. Is it the responsibility of the healthcare facility to validate the medical device in a sterilization process?

A. No. The HDM is required to validate the medical device(s) in a standard published healthcare cycle.

Q. Who is ultimately responsible for patient safety?

A. The HDM and the healthcare facility.

Q. What are some of the organizations that can direct healthcare and HDMs?

A. 1. Association for the Advancement of Medical Instrumentation (AAMI)

2. International Association of Healthcare Central Service Material Management (IAHCSMM)

3. Food and Drug Administration (FDA)

4. Association of periOperative Registered Nurses (AORN)

Becki Harter, CST, CRCST, is president and CEO of Indianapolis-based consulting firm Sterilization by Design.

Validation Cycles
Wrapped: half cycle Unwrapped (flash): half cycle
275(gravity)- 5 min sterilize and 15 min dry time 275- 1 to 2 min sterilize
275 (pre-vac)-1 to 2 min  and 7 to eight minutes sterilize dry time 275(pre-vac/gravity)- 1 to 2 min sterilize no dry time
270 (gravity)-7 to 8 min sterilize and 15 min dry time 270-(gravity) 2 to 5 min sterilize no dry time
270 (pre-vac)- 2 min sterilize and  10 to 12 min dry time 270-(pre-vac) 2-5 min no dry time2
50 (gravity)- 15 min sterilize and  7-15 min dry time 250 (gravity/pre-vac)-none

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