CH 15: Low-Temperature Sterilization

Introduction

• Ethylene Oxide (EtO)
• Hydroden Peroxide (H2O2)
• Ozone (O3)

Low Temperature Sterilization Requirements

• Efficacy (Effectiveness): Provides the minimum-required Sterility Assurance Level (SAL).
• Safety: No toxic residues on packaging/devices upon completion of sterilization cycles.
• Exposure Monitoring.
• Sterilization Performance Monitoring.
• Penetration.
• Material Compatibility.
• Adaptability.
• Approval.

Efficacy

• FDA regulated.
• FDA/CDC outlines the SAL for each sterilization method.

Toxicity Standards: Low-Temp Sterilants

• PEL: Permissible Exposure Limits; parts per million (ppm). By OSHA.
• TWA: Time Weighted Average (over an 8 hour day). By OSHA.
• IDLH: Immediately Dangerous to Life or Health. National Institute for Occupational Safety and Health (NIOSH) established.
• EtO: OSHA PEL/TWA (1.0 ppm), NIOSH IDLH limit (800 ppm). Monitoring required.
• H2O2: OSHA PEL/TWA (1.0 ppm), NIOSH IDLH limit (75 ppm). Monitoring is not required.
• O3: OSHA PEL/TWA (0.1 ppm), NIOSH IDLH limit (5 ppm). Monitoring is not required.

Penetration

• Eto inactivates microbes (alkylation).
• H2O2/O3 destroys microbes (oxidation).

Ethylene Oxide

• For heat and moisture-sensitive medical devices.
• High vapor pressure and a low boiling point of 51.3 F
• EtO cartridges are placed inside chambers of less than 10 cubic feet. The cartridge is punctured under vacuum.
• Sterilization Cycle 5 Stages: Preconditioning and humidification, gas introduction, exposure, evacuation and air washes.
• Cycle: About 2 1/2 hours, excluding aeration time.
• After sterilization items must go through an aeration process (removes residual EtO before the chamber can be unlocked for item removal).

Safety

• OSHA classifies EtO as a carcinogen and reproductive hazard.
• EtO Sterilizers: Located in a well ventilated area/ air exchange rate of at least 10 changes per hour/ in negative-pressure rooms.

EtO Sterilization Process Parameters

• Gas Concentration: 45 to 1,200 mg/l
• Temperature: 98 F to 145 F
• Relative Humidity: 40% to 80%
• Exposure Time: 1 to 6 hours
• Aeration Time: 8 to 12 hours at 122 F to 140 F

Exposure Monitoring

• Devices affixed to the employee's clothing/breathing zone (within 1 foot of the person's nose) tests airborne EtO concentrations.

Materials Compatibility

• EtO should not be used to sterilize: 1) Liquids, 2) Devices with energy sources (sparks are created), 3) Leather Items (chemicals used in the tanning process will combine with EtO and form chlorohydrin)

Packaging

• EtO paper/plastic or Tyvek peel pouches, approved fabric wrappers, medical crepe paper, polypropylene and most container systems.
• Never use aluminium foil, cellophane, nylon films, polyester, PVC (plastic) films and styrofoam.

Aeration

• Vacuum pulse remove EtO.
• Warm air circulates to remove residuals from instruments. Minimum 8 hours at 140 F and 12 hours at 122 F.

Sterilizer Performance Monitors

• Bacillus atrophaeus: Microorganism of choice for EtO.

Hydrogen Peroxide Systems

• Hydrogen Peroxide Gas Plasma: Oxidative Process. Safer than EtO, rapid cycle times. Byproducts of the cycle (water and oxygen) are nontoxic = no aeration phase.
• Gas plasma are highly ionized gases.

Efficacy

• H2O2 Gas Plasma: Hydrogen Peroxide solution from 59% to 95% is proven effective at killing microorganisms.

Penetration

• H2O2 gas plasma sterilizers sterilize some single channel flexible endoscopes, cameras, rigid endoscopes, light cords, batteries and power drills.

Types of H2O2 Gas Plasma Systems

• Compact Systems: 28-38 min processing times.
• Large Capacity Systems: 75 min cycle times.

Sterilization Cycle/Process Parameters

• Phases of hydrogen peroxide gas plasma.
• 1)Vacuum: The load is heated. Removes remaining water as it evaporates.
• 2)Injection: H2O2 into chamber.
• 3)Diffusion: Drives H2O2 vapor into small crevices/lumens of devices.
• 4)Plasma: A vacuum decreases the pressure/radio frequency (RF) energy is radiated from an electrode screen. RF energy ionizes the H2O2 creating H2O2 gas plasma.
• 5)Vent: No aeration. Use instruments after the 24-75 min sterilization cycle.

H2O2 Gas Plasma:Process Parameters

• Time: 24-75 mins.
• Cycle Temperature: Less than 131 F
• Hydrogen Peroxide Concentration: 59% to 95%
• Vacuum Level: Automatically controlled.
• Plasma: Automatically controlled.

Safety

• H2O2 liquid irritates skin/damages eyes.
• In vapor phase: Irritates eyes,nose, throat, and lungs.
• H2O2 is packaged in sealed cassettes. Chemical leak indicators on them change from yellow or white to red.
• After 5 sterilization cycles the cassette is automatically ejected into a collection box for safe disposal.
• Latex, vinyl (PVC), or nitrile gloves are worn to remove items from a cancelled cycle.

Materials Compatibility

• H2O2 gas plasma is not compatible with:
• 1) Liquids and powders.
• 2) Any material that absorbs liquid.
• 3) Items that contain cellulose, such as cotton, paper or cardboard, linens, huck towels, gauze sponges or any item containing wood pulp.

Packaging

• Tvek pouches are compatible.
• Don't use cellulose-containing packaging such as paper/plastic pouches.

Sterilizer Performance Monitors

• Geobacillus Stearothermophilus: Microorganism of choice for H2O2 gas plasma.
• AORN Guidelines: Daily biological monitoring.

Vaporized Hydrogen Peroxide

• "VHP": used since 2007.
• 59% hydrogen peroxide solution.
• Injected 4 times during each sterilization cycle. After the 4th injection period, the load is automatically aerated in the sterilizer. VHP is converted to water and oxygen.

Types of Vaporized H2O2 Systems

• Single Preprogrammed 55 Min Cycle: Lumened and nonlumened instruments and devices.
• Two Preprogrammed Cycles: 28 min (non lumened instruments) and 55 min (instruments with lumens/non stainless steel mated surfaces)

Sterilization Cycle Process Parameters

• Phases of VHP systems include:
• 1) Conditioning: Removes air/excess moisture then recharges with dry sterile air.
• 2) Leak Test: Vacuum is held to ensure a leak tight chamber.
• 3) Sterilization: 4 injection pulses, each followed by a hold period.
• 4) Aeration: Automatic.

Vaporized H2O2: Process Parameters

• Cycle Tempeerature: Less than 122 F
• H2O2 Concentration: 59%
• Time: 28 to 55 mins.

Safety

• Concentrated H2O2 is corrosive to skin, eyese, nose, throat, lungs, and gastrointestinal tract.
• Wear latex, vinyl (PVC), or nitrile gloves when removing items from a cancelled load.

Materials Compatibility

• Vaporized H2O2 sterilization is compatible with telescopes, cameras, light cables. batteries and many lumened devices.
• The VHP system is not intended to process liquids, linens, powders, or any cellulose materials.

Packaging

• Polywrap, nonwoven sterilization packaging made of 100% polypropylene, Tyvek.

Sterilizer

• Geobacillus Stearothermophilus: Microorganism of choice for VHP.

Ozone Sterilization

• "O3"
• FDA clearance in 2003.
• No aeration needed.
• Medical devices/surgical instruments can be used as soon as the 4 1/2 hour cycle is complete.

Ozone Sterilization Process Parameters

• Cycle Temperature: 87.4 F to 97 F
• Ozone Concentration: 59%
• Relative Humidity: 85% to 100%
• Time: 4 hours and 30 mins.

Safety

• OSHA,FDA, and NIOSH regultae O3 as a toxic gas.
• O3 = Bluish gas/pungent odor (odor threshold 0.003 to 0.01 parts per million/ppm)
• O3 sterilizer design converts all O3 produced to oxygen before being exhausted into the room.

Exposure Monitoring

• O3 sterilization requires a well ventilated room with 10 air exchanges per hour.

Materials Compatibility

• O3 process is not recommended for sterilizing sealed ampules, liquids, natural rubber, latex and fabrics.

Sterilizer Performance Monitors

• Geobacillus Stearothermophilus: Microorganism of choice for O3.