10 Things You Need to Know About Ethylene Oxide (EO) Sterilized Medical Devices
Ethylene oxide (EO) is a gas used to sterilize medical devices, particularly devices that are unable to be sterilized with traditional high heat. As medical devices must pass specific sterility standards before being used on patients, ethylene oxide sterilization is a simple, effective, and common heat sterilization alternative. However, ethylene oxide and its byproducts, (ECH) ethylene chlorohydrin and (EG) ethylene glycol, are toxic to the human body. Thus, all EO sterilized medical devices must meet certain regulatory limits for EO, ECH, and EG residuals. The following are ten things you need to know about ethylene oxide sterilized medical devices.
#1 Certain EO sterilized devices will not need EO residual testing
Ethylene oxide sterilized devices with no patient contact (such as in vitro diagnostic devices) are not covered by the ISO 10993-7 EO residual limits standard. In other words, only devices that are EO sterilized and have patient contact must have EO residual testing, as EO toxicity is not a risk if a patient isn’t in contact with the EO residuals.
#2 Side effects of ethylene oxide and its residual components are:
- Irritation
- Organ damage
- Mutagenicity
- Carcinogenicity
These side effects are why ethylene oxide residual limits have been set for medical devices and other products terminally sterilized with EO that involve patient contact.
#3 Typically, only EO and ECH residuals are assessed during EO residual testing
Levels of ethylene oxide, ethylene chlorohydrin, and ethylene glycol must meet specific limits. However, ethylene glycol poses minimal risk to the patient during regular product use. The amount of EG found in a medical device is likely smaller than the calculated allowable limits, so devices that meet EO and ECH limits will automatically meet any required EG limits. As a result, only ethylene oxide and ethylene chlorohydrin are assessed for EO residual testing in most cases.
#4 EG limits are of concern for specific devices
The potential exists for accelerated blood cell destruction following a rapid intravenous administration of EG. For devices contacting intravenous blood flow, especially for lengthy periods, tests should be performed to measure the hydrolysis of EO to EG to prevent hemolysis.
#5 There are three medical device categorizations for EO residual testing
EO sterilized devices are categorized as either:
- Limited exposure
- Prolonged exposure
- Permanent exposure
Please see our article about 3 Limits You Must Meet For Ethylene Oxide Residual Testing for additional details about EO residual limits.
#6 There are special considerations for multi-device systems
For multi-device systems, the EO limits apply to each individual device that contacts a patient. Thus, EO residual testing must be performed for each device of a multi-device system.
#7 There are special EO limits for certain medical devices
Devices with special EO limits include:
- Blood cell separators
- Intraocular lenses
- Blood oxygenators
- Cardiopulmonary bypass devices
- Blood purification devices
- Drapes (contacting intact skin)
#8 Tolerable contact limits are required for surface contacting devices and implants
In addition to limits of EO and ECH by device category, tolerable contact limits for surface contacting devices and implants are also required. Thus, it is essential to determine the surface area of each device that comes in contact with the patient and to extract the EO and ECH residues from each medical device sample.
Please see our article about 5 Calculations You Need To Know To Determine EO Residuals For Your Device for additional details on how to calculate tolerable contact limits.
#9 There are two methods for extracting EO from medical devices for EO residual testing
The choice of EO extraction (simulated use or exhaustive) for each product is selected based on the device’s intended use. For example, many blood-contacting and parenteral devices would be extracted using simulated use extraction.
Please see our article about Simulated Use vs. Exhaustive Extraction for additional details on the differences between simulated use extraction and exhaustive extraction methods for EO residual testing.
#10 How quickly you ship sample sterilized devices to your contract testing facility after EO sterilization impacts how well these samples represent the rest of the sterilized batch
Removal of the product samples from an EO sterilized batch soon after a sterilization cycle is completed and shipment to a laboratory or storage in the laboratory for later analysis can jeopardize the correlation of sample EO residual levels to the actual EO residuals for the rest of the batch. Ensure that you give the EO sterilized devices ample time to rest with the entire set of sterilized devices following the sterilization cycle before shipping them off. Also, when preparing shipments, make sure to include the date and time the samples were extracted following their EO sterilization cycle.
Summary
Overall, ethylene oxide residual testing is a critical series of regulatory tests and ensures EO and ECH residuals following EO sterilization do not result in patient toxicity when a medical device is in use. The ten EO residual testing facts above will support you in determining what EO residual testing entails and which EO residual limits are relevant to your medical device.
Ethide Labs is a contract testing organization that specializes in EO Residual Testing. Ethide Labs also offers Bioburden Testing, Environmental Monitoring, Sterilization Validations, Microbiology Testing, Bacterial Endotoxin Testing, Package Integrity Testing & Cytotoxicity Testing services for medical device companies and allied industries. Ethide is an ISO 13485 certified facility.
References
International Organization for Standardization. Biological evaluation of medical devices — Part 7: Ethylene oxide sterilization residuals. Geneva (Switzerland): ISO; 2008. (ISO 10993-7:2008).
