Sterilization Unwrapped

May 1, 2003

Sterilization Unwrapped

By Becki Harter, CST, CRCST

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

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

Organizations such as the Food and Drug Administration (FDA), Association forthe Advancement of Medical Instrumentation (AAMI) and the InternationalAssociation of Healthcare Central Service Material Management (IAHCSMM) havebeen prompted to write standards and develop protocol for sterilizationprocesses, that has played an integral role in the safety and effectiveness ofmedical 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 bevalidated and tested in a laboratory setting to determine its safety andeffectiveness for use in a healthcare setting. The validation process has beendeveloped using the published standard healthcare cycles for each sterilizationprocess. Validation of a medical device in a sterilization process requires thefollowing 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 safetyand effectiveness in a published standard healthcare cycle. Chemicalsterilization processes do not have half cycles. Sterility assurance level mustbe reached in a full cycle only.

Some Problems Seen in Healthcare

Validation and test methodology have been developed using published standardhealthcare cycles. What that means is that the FDA and the AAMI have developedtesting protocol to mirror the tested, validated and published sterilizationprocesses used in healthcare today. The published standard healthcare cyclesseen today are supported by test data specific to the sterilization process,device and the respective microorganisms that present the greatest challenge tothat process. Sterility assurance levels of 10 to the minus sixth (one part permillion), is the level of microorganism colony growth that would be considerednot harmful to humans or able to produce disease.

Q. What happens if a healthcare device manufacturer (HDM) does notadhere to the published standard healthcare cycles?

A. Patient safety is compromised. There are some HDMs that do notroutinely adhere to the published standard healthcare sterilization cycles.Manufacturers of orthopedic and neurological medical devices are two types ofHDMs 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 minutessterilize 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 controland 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/testmethodology 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 nothave dry times listed are more often than not for unwrapped cycles only.

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

A. Yes. If a medical device is sterilized in a wrapped cycle utilizingdata compiled for an unwrapped cycle, patient safety has been compromised and aninfection control risk created. If the HDM has validated for unwrapped cyclesonly, the medical device can be sterilized in an unwrapped cycle only until theHDM does testing in a wrapped cycle. Wrapped cycles create an additionalchallenge to the sterilization process and must be tested/validated separatelyfor 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/testmethodology summary. If there is any doubt, ask. Patient safety is the No. 1concern.

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

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

  • 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 (www.fda.gov) 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 themedical device in a sterilization process?

A. No. The HDM is required to validate the medical device(s) in astandard 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 andHDMs?

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

2. International Association of Healthcare Central Service MaterialManagement (IAHCSMM)

3. Food and Drug Administration (FDA)

4. Association of periOperative Registered Nurses (AORN)

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

Validation Cycles Steam
Wrapped: half cycleUnwrapped (flash): half cycle
275(gravity)- 5 min sterilize and 15 min dry time275- 1 to 2 min sterilize
275 (pre-vac)-1 to 2 min  and 7 to eight minutes sterilize dry time275(pre-vac/gravity)- 1 to 2 min sterilize no dry time
270 (gravity)-7 to 8 min sterilize and 15 min dry time270-(gravity) 2 to 5 min sterilize no dry time
270 (pre-vac)- 2 min sterilize and  10 to 12 min dry time270-(pre-vac) 2-5 min no dry time2
50 (gravity)- 15 min sterilize and  7-15 min dry time250 (gravity/pre-vac)-none