Medical Sterilization Methods and Validation Protocols

Dry Heat Sterilization

Incineration

Incinerators or crematoriums are used to sterilize and destroy residual infectious material.

Direct Flame

Apply the material directly to the flame of a Bunsen burner or alcohol lamp for a few minutes. This is commonly used for inoculating loops in microbiology laboratories.

Hot Air Ovens (Poupinel)

These utilize hot air circulation. Due to the requirement for high temperatures and long exposure times, they are rarely used in modern hospital settings.

Ethylene Oxide Gas Sterilization

Along with the autoclave, this is one of the most common methods used in hospitals. Ethylene oxide is a colorless gas at room temperature with a density nine times that of air. It is toxic by inhalation and contact, as well as flammable and explosive. It is typically mixed with other gases to mitigate these risks. It effectively eliminates microorganisms with high penetrating power without damaging materials. It is used at temperatures between 30°C and 60°C. Once the process is complete, the material must be aerated to eliminate toxicity.

Phases of the Ethylene Oxide Process

• Conditioning: Preheating the chamber, placing the material, closing the chamber, and removing the air.
• Gas Exposure: Introducing water vapor and the gas for the required duration.
• Gas Evacuation: Removal of gas via vacuum.
• Aeration: Introducing filtered air multiple times.

Sterilization by Liquids

Peracetic acid is used by immersing materials, often in microsurgery, for 30 minutes. The device is compact and typically found in clinical settings.

Sterilization Validation and Controls

The objective is to ensure the efficacy of the sterilization process.

Physical Controls

Monitoring and charting values such as pressure, temperature, time, and humidity.

Chemical Controls

Chemical compounds change color upon contact with the sterilizing agent:

• External: Indicates that the sterilizing agent reached the surface of the package.
• Internal: Placed inside the container to verify sterilization conditions within the package.
• Functional: Used specifically in autoclaves to ensure steam reaches all parts of the apparatus. The Bowie-Dick test is the most common chemical control; it uses paper impregnated with a compound that changes color if the autoclave is functioning correctly.

Biological Controls

Devices containing spores of microorganisms are subjected to the sterilization process. They are then incubated to determine if any growth occurs; if no growth is observed, the sterilization process was successful.