Sterrad sterilization is a low-temperature method used in healthcare settings to reprocess medical equipment. This process offers a gentle approach for sterilizing instruments sensitive to heat and moisture. It provides an effective means of pathogen inactivation, ensuring the safety of patients and healthcare providers.
The Hydrogen Peroxide Gas Plasma Process
The Sterrad system employs a multi-phase process to achieve sterilization, beginning with a vacuum phase. The sterilization chamber is first evacuated to a deep vacuum, removing air and moisture. This prepares the instruments for optimal interaction with the sterilant and facilitates its penetration into instrument lumens and surfaces.
Following the vacuum, a measured amount of concentrated hydrogen peroxide (H2O2) solution is injected into the chamber. This liquid hydrogen peroxide quickly vaporizes, diffusing throughout the chamber and surrounding the medical instruments. The vaporized hydrogen peroxide then permeates packaging and intricate internal channels of devices, acting as the primary sterilant.
After sufficient diffusion, radiofrequency (RF) energy is applied to the chamber, creating an electric field. This energy breaks down the hydrogen peroxide vapor into a gas plasma, a state of matter containing reactive free radicals, ions, and electrons. These highly reactive species, such as hydroxyl and hydroperoxyl radicals, are responsible for the antimicrobial action. They disrupt the cellular components of microorganisms, including their DNA, RNA, proteins, and cell walls.
In the final venting phase, the RF energy is turned off, and the plasma extinguishes. The remaining reactive components of the hydrogen peroxide gas plasma recombine, converting back into harmless water vapor and oxygen. These byproducts are then vented from the chamber through high-efficiency particulate air (HEPA) filters. This process ensures no toxic residues remain on the instruments.
Applications in Medical Settings
Sterrad sterilization is primarily used for medical devices that cannot tolerate the high temperatures and moisture levels of traditional steam autoclaves. This low-temperature method preserves the integrity of complex electronic components. It is particularly suitable for instruments used in minimally invasive surgeries, where advanced optics and electronics are common.
Specific examples of commonly sterilized items include flexible endoscopes, which contain delicate lenses and fiber optics that would be damaged by heat. Rigid endoscopes, surgical cameras, and light cords also benefit from this process due to their intricate designs and sensitive materials. Batteries, power drills, and instruments incorporating certain plastics or electronic circuits are routinely processed using this method.
Material and Device Compatibility
While effective for many instruments, Sterrad sterilization has specific limitations regarding material and device compatibility. Cellulose-based materials, such as paper wraps, cotton towels, and linen products, are incompatible with the process. These materials absorb hydrogen peroxide, which can interfere with the sterilization cycle by reducing the sterilant concentration in the chamber and preventing proper gas plasma formation.
The system is designed for surface sterilization and cannot effectively penetrate liquids or powders. The presence of moisture can quench the plasma and dilute the hydrogen peroxide, compromising the sterilization process. Instruments must be thoroughly cleaned and dried before being placed in the Sterrad system to ensure efficacy.
Limitations also exist for devices with long, narrow, or dead-end channels, known as lumens. While the hydrogen peroxide vapor can diffuse into these channels, the effectiveness of plasma generation and radical penetration can be reduced in very restrictive geometries. Certain Sterrad models or accessories, such as lumen boosters, are designed to enhance sterilant penetration and efficacy within specific lumen dimensions. Other materials that readily absorb the sterilant, such as some types of rubber or certain polymers, may also be unsuitable for this process.
Comparison with Traditional Sterilization Methods
Sterrad technology stands apart from traditional sterilization methods like steam autoclaving and Ethylene Oxide (EtO) sterilization due to its operational characteristics. Steam autoclaving relies on high temperatures, typically 121°C (250°F) to 132°C (270°F), and pressurized steam to sterilize heat-stable items. In contrast, Sterrad and EtO are low-temperature methods, operating at much lower temperatures, generally below 60°C (140°F), making them suitable for heat-sensitive instruments.
Cycle time is another significant differentiator. Sterrad cycles are comparatively fast, often completed in under an hour. Ethylene Oxide sterilization, while also low-temperature, requires lengthy aeration periods, sometimes extending for several hours or even days, to remove toxic EtO residues from sterilized items. This extended aeration is necessary because EtO is a known carcinogen.
Regarding toxicity and byproducts, Sterrad offers a notable advantage. Its byproducts are non-toxic, consisting primarily of water vapor and oxygen, which are safely vented into the environment. This contrasts sharply with EtO, which is a hazardous gas requiring strict handling and disposal protocols due to its carcinogenic and mutagenic properties. While steam autoclaving also produces non-toxic byproducts, its high heat limits its material compatibility.