Cause of Device-Related Incident
Device factors

Clinical Specialty or Hospital Department
*Not stated; Clinical/Biomedical Engineering; CSR / Materials Management

Device Factors
Design / labeling error

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Electrical shock / electrocution; Failure to deliver therapy; Fire

Support System Failures
*Not stated

Tampering and/or Sabotage
*Not stated

User Errors
*Not stated

UMDNS
Plugs, Hospital Grade [15-850]; Sterilizing Units, Ethylene Oxide [13-740]

EtO Sterilization of Medical Devices



Hazard [Health Devices Mar-Apr 1979;8(5-6):147]

Problem

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.

Discussion

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.

Recommendations

  1. 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 another type.
  2. 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.
  3. 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.

UMDNS Terms

  • Plugs, Hospital Grade [15-850]
  • Sterilizing Units, Ethylene Oxide [13-740]

Cause of Device-Related Incident

Device factor: Design error

Mechanism of Injury or Death

Electrical shock/electrocution; Failure to deliver therapy; Fire


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