Steam sterilization has many benefits as a sterilization method in healthcare facilities including low cost, safety, and efficacy. When processing heat and moisture stable materials, the speed and productivity of a steam sterilizer are advantages over other forms of sterilization. Medical devices that can be processed in a steam sterilizer include surgical instruments, implantable medical devices and surgical linens. Sterile Processing Department staff should always follow the device manufacturer’s instructions for use when processing the device. Steam sterilization is considered a reliable and consistent method of sterilization throughout healthcare facilities.
How does steam sterilization work with an autoclave?
Autoclaves come in a variety of sizes and offer different functions, which means there are several uses for an autoclave. These devices use pressurized steam to efficiently sterilize the tools inside. When someone uses simple disinfectant to “sterilize” equipment, it isn’t nearly as effective as it should be. An autoclave brings the temperature inside to above boiling point, which ensures everything inside is free of bacteria and other contaminants. Without the proper temperature and method used in autoclaves, equipment and tools won’t be completely sterilized. Finally, because many medical devices have tiny surfaces and components, sterilizing these tools by hand can be both time consuming and ineffective. With steam sterilization, every surface of the tool can be completely sterilized, preventing the spread of disease.
Why is steam the preferred method for killing micro-organisms?
One of the most effective ways to transfer heat energy is via humidity, contained within steam. Moist heat (steam) is proven to be more effective than dry heat for killing a wide range of micro-organisms due to its ability to penetrate microbial cells. This type of heat energy kills micro-organisms by denaturing their proteins which causes a loss of the proteins three-dimensional functional shape. Think of a wound caused by boiling water or water vapor versus a wound caused by being exposed to dry heat. The wound that resulted from moist heat will hurt more and go much deeper than the one caused by dry heat.
Due to the increase of pressure and steam generation within an autoclave, this allows for the temperature within the chamber to reach above boiling point (100 ºC) and allow for the elimination of a wider range of micro-organisms (including bacterium spores). To eliminate bacterium spores and all micro-organisms, the temperature needed should be above 130ºC for quick a sterilization cycle (5 minutes) or above 120ºC for a longer sterilization cycle (20-30 minutes). Exposing the micro-organisms to a high temperature with a short timing cycle, or under a low temperature with a longer timing cycle will both be effective in eliminating the micro-organisms, as there is only a specific amount of time all bacterium can survive under these temperature conditions.
Steam is widely available since there are only two ingredients needed: water and a source of heat. Since every surgery in Australia and New Zealand has and must have access to water, it follows that finding water for operating the autoclave is reasonably likely and reliable. In addition to being available, steam is also cost-effective. Since the steam sterilizer, or autoclave, does not require the use of any other chemicals, it’s relatively inexpensive to operate.
Autoclaves require water to generate steam; however, tap water is not the appropriate option. Tap water contains a wide range of minerals and impurities which have the capacity to abort your autoclave cycle, and over time will calcify the internal chamber and components, leading to increased maintenance. The safer option to preserve the longevity of your autoclave is to use or connect a Reverse Osmosis filter to your tap water feed, or to purchase distilled/demineralized water. However, comparing the long term cost of a Reverse Osmosis filter and purchasing distilled water – the RO system works out to be less expensive to operate in the long run (requiring minimal maintenance, once every 12 months). This system allows for the water to be purified and therefore improves the life of the equipment.
Unlike many other sterilizing agents, steam is non-toxic. Since steam is a form of water vapor produced by boiling, and essentially has the same properties of water. However, one should always take precautions to not get burnt by hot steam. As steam is a form of water vapor and there is no extra chemicals required, this eliminates the need for storage of hazardous chemicals.
Steam (moist heat) is able to strike micro-organisms faster than dry heat, and that’s due to steam being able to transfer heat faster than hot air. For example, it takes two hours at 160ºC to kill bacterium spores under dry heat, whether as steam will have all micro-organisms eliminated within five minutes at 134ºC due to the denaturing of the micro-organism proteins. Therefore, steam or moist heat requires a shorter sterilization time in comparison with dry heat.