EtO Sterilization of Medical Devices
Hazard [Health Devices Mar-Apr 1979;8(5-6):147]
A member hospital reported failure of the clear polycarbonate (Lexan)
blade assembly on specific brand of hospital grade plugs. This assembly holds the blades
in place and permits visual inspection of terminals after wiring. Failure of the assembly
allows one or all of the blades to move back into the body of the plug, making the plugs
dangerous or unusable. The ground blade pushes back into the body, resulting in loss of
ground continuity. The power blades could also short against each other when pushed back
into the body, although no such cases have been reported.
It is well known that certain materials will not withstand repeated
ethylene oxide (EtO) sterilization. However, many hospitals and device manufacturers do
not realize that certain materials, unaffected by exposure to pure EtO, will be attacked
by Freon at high temperatures. (Since pure EtO is explosive, many sterilizers especially
large ones use a nonflammable mixture of 88% Freon, 12% EtO.) Polycarbonate, trademarked
as Lexan or Merlon, is one such material.
ECRI traced this failure to repeated exposure to a mixture of 88% Freon,
12% EtO. Exposure will cause crazing and cracking of the polycarbonate, which could
subsequently fail under stress. Through tests, the plug manufacturer determined that 100%
EtO will not cause these problems and is currently studying possible solutions.
Although the reported problem occurred with one manufacturer's line of plugs, it
will occur in other plugs or components manufactured of polycarbonate and sterilized in
88% Freon, 12% EtO.
- Check the EtO mixture in the sterilizers in your
hospital. If an 88%, 12% EtO mixture is used, do not sterilize polycarbonate
products. If only the power plug contains polycarbonate, replace it with
- Check with the device or sterilizer manufacturer to
see whether other materials may be affected by exposure to EtO, Freon, or
heat (sterilizer temperatures may reach 70° C [158° C]). Inform the
manufacturer of your hospital's EtO mixture and sterilizing temperature.
Aeration times and temperatures may also be important.
- Inspect plugs and other products containing polycarbonate or other
materials that have been sterilized in EtO for cracking or stickiness (a
sign of depolymerization of plastics). If any of these is present, replace
the plug or component.
- Plugs, Hospital Grade [15-850]
- Sterilizing Units, Ethylene Oxide [13-740]
Cause of Device-Related Incident
Device factor: Design error
Mechanism of Injury or
Electrical shock/electrocution; Failure to deliver therapy; Fire