Medical sterilization prepares reusable surgical instruments for patient use, preventing the spread of infection. Traditional methods rely on high temperatures or moisture, which can damage the complex and sensitive materials used in modern medical equipment. The Sterrad system offers a modern, low-temperature sterilization technology designed to safely process these delicate instruments.
Defining the Sterrad System
Sterrad is the registered trademark name for a line of sterilization systems developed by Advanced Sterilization Products (ASP). This self-contained unit uses a patented hydrogen peroxide gas plasma process to inactivate microorganisms on medical devices. The system hardware includes a sterilization chamber, typically constructed from aluminum, along with an on-board vacuum pump to control pressure. Hydrogen peroxide is delivered via disposable, single-use cassettes, making the delivery of the sterilant both contained and standardized.
The Science of Plasma Sterilization
The sterilization process is a multiphase cycle combining hydrogen peroxide vapor and gas plasma. The process begins with a vacuum phase, where the chamber is evacuated to reduce internal pressure. Next, a measured amount of aqueous hydrogen peroxide solution, typically 59% nominal concentration, is injected, heated, and vaporized. This vapor diffuses throughout the chamber, permeating the packaging and contacting all surfaces of the medical devices to begin the inactivation of microorganisms.
After the vapor diffusion phase, the system applies radiofrequency (RF) energy to the chamber. This energy excites the hydrogen peroxide molecules into a low-temperature gas plasma, often described as the fourth state of matter. During this plasma phase, the hydrogen peroxide vapor breaks apart into highly energetic species called free radicals. These free radicals destroy any remaining microbial life, ensuring a high sterility assurance level.
The plasma phase is responsible for the system’s safety profile by actively breaking down the remaining hydrogen peroxide. Once the electromagnetic field is terminated, the energized components recombine. This forms only non-toxic byproducts: oxygen and water vapor.
Advantages Over Traditional Sterilization Methods
The Sterrad system operates at a low temperature, typically between 47°C and 56°C, making it safe for heat-sensitive devices. Traditional steam sterilization (autoclave) uses high heat and moisture, which can damage materials like plastics, rubber, and polymers found in delicate instruments. The low-temperature, dry environment of the gas plasma process preserves the integrity and extends the lifespan of these surgical tools.
The process offers operational and safety advantages compared to chemical methods like ethylene oxide (EtO) sterilization. EtO is a toxic gas that requires a lengthy aeration period, often 8 to 12 hours, to remove all toxic residues. The Sterrad system eliminates this aeration step because the gas plasma technology converts the sterilant into harmless water and oxygen.
Eliminating the aeration period contributes to a faster instrument turnaround time, allowing devices to be sterilized and ready for reuse quickly. Total processing time ranges from 24 to 60 minutes, depending on the model and selected cycle. This is an efficiency gain over EtO’s multi-hour cycles and minimizes chemical exposure for healthcare workers.
Healthcare Applications and Logistics
The Sterrad system is widely used for processing instruments that cannot tolerate the heat and moisture of steam sterilization. Applications include delicate tools used in minimally invasive surgery, such as rigid and flexible endoscopes. The system is also used for sterilizing cameras, light cords, batteries, and orthopedic power tools.
The process is effective even for instruments with difficult-to-reach areas, such as the hinges on forceps and scissors, which are known as diffusion-restricted spaces. Cycle duration varies depending on the sterilizer model and the type of load being processed, with cycle times ranging from an Express cycle of 24 minutes to a Duo cycle of 60 minutes. Proper instrument preparation is a prerequisite for successful sterilization, meaning devices must be thoroughly cleaned and dried before being loaded into the chamber.