What are the recommended safety and operational guidelines for using ethylene oxide (EtO) sterilization of heat‑sensitive medical devices in a clinical setting?

Ethylene Oxide (EtO) Sterilization: Safety and Operational Guidelines

Ethylene oxide sterilization should only be used in healthcare facilities with specialized equipment, strict environmental controls, and specially trained staff due to its significant toxicity, carcinogenicity, and flammability risks. 1

When EtO Sterilization is Appropriate

EtO is the only sterilization method that is both effective and compatible with heat-sensitive flexible endoscopes (particularly high-risk devices like duodenoscopes), but it comes with major operational drawbacks. 1

Key Indications:

• Heat-sensitive medical devices that cannot tolerate temperatures above 60°C 1
• Flexible endoscopes requiring true sterilization (not just high-level disinfection) 1
• Devices with complex internal channels where other methods fail 1

Critical Safety Requirements

Personnel and Facility Requirements:

• Only facilities with specially trained staff should operate EtO sterilizers 1
• Approximately 100,000 workers in the U.S. are regularly exposed to EtO, making proper training essential 2
• Strict environmental controls and proper ventilation systems are mandatory 1, 3

Health Hazards:

• EtO is toxic and carcinogenic, causing serious eye irritation, sore throat, difficulty breathing, blurred vision, and increased cancer risk 1
• NIOSH recommends treating EtO as a potential carcinogen 2
• The gas is flammable and can trigger explosive chain reactions 1

Operational Guidelines

Pre-Sterilization Requirements:

• Devices must be thoroughly cleaned manually before EtO sterilization 1
• For endoscopes: perform point-of-use treatment, manual cleaning, followed by high-level disinfection (HLD) before EtO sterilization 1
• Fit EO venting caps according to manufacturer's instructions 1
• Ensure proper packaging or containment of instruments 1

Sterilization Process:

• Use low-pressure or subatmospheric EtO sterilizers operating below 60°C 1
• Place endoscopes in disinfection bags or containers with internal indicators 1
• Document temperature and time of sterilization according to manufacturer's Instructions for Use (IFU) 1
• Biological indicators (spore tests) are required for routine monitoring 1

Critical Timing Considerations:

• Total processing time ranges from 1-7 days, including sterilization, indicator incubation, and aeration 1
• Aeration period requires 8-12 hours to remove toxic residual gas 1
• This lengthy turnaround makes EtO unsuitable when rapid instrument turnover is needed 1

Ventilation and Exposure Control

Local Exhaust Ventilation:

• EtO plumes flow upward when sterilizer doors open, with highest concentrations at upper locations 2
• Local exhaust ventilation significantly reduces EtO concentrations and exposure duration 2
• Proper ventilation of sterilizers, aerators, and working spaces is essential 3

Common Exposure Pitfalls to Avoid:

• Improper or inadequate ventilation systems 3
• Improper handling or storage of sterilized items 3
• Untrained workers operating equipment 3
• Poor sterilization facility design 3
• Opening sterilizer doors without proper exhaust capture 2

Verification and Quality Control

Monitoring Requirements:

• Use biological indicators (spore tests) for routine monitoring 1
• Monitor sterilizer chamber temperature and relative humidity (typically 38-54°C and 30-50% RH) 2
• Verify proper aeration to prevent toxic residue contamination 1, 4

Post-Sterilization Testing:

• Cytotoxicity testing should verify that degassed sensors/devices do not contaminate with EtO residues 1
• Follow manufacturer's recommended degassing periods strictly 1

Alternative Considerations

Given EtO's significant drawbacks, consider peracetic acid (PAA) as a more practical alternative for endoscope sterilization when feasible. 1 PAA is FDA-approved as a liquid chemical sterilant, is more environmentally friendly, and poses fewer health risks to staff, though it requires adherence to manufacturer's IFU regarding concentration, temperature, and exposure time. 1

Gas plasma sterilization (hydrogen peroxide-based) is not suitable for flexible endoscopes because vapor cannot effectively reach long, narrow internal channels with bends. 1

Regulatory Compliance

• Follow ISO 10993-7 standards specific for EtO sterilization 1
• Ensure sterility assurance level (SAL) of 10⁻⁶ is achieved 1
• Comply with COSHH regulations regarding ventilation and personal protective equipment 1
• Inform instrument and processing equipment manufacturers when using EtO, as it may affect warranties 1