Set Your Sights on Safe Sterilizing. What should you know about tabletop steam sterilizers?

Improper sterilization of medical devices and surgical instruments can present major risks to patients, including life-threatening infections.

Successful sterilization is vital to ensure peace of mind for the facility and the patient. Tabletop sterilization is a well-established technology; therefore, this can be achieved if all proper procedures are followed. The information below takes an in-depth look at tabletop steam sterilizers, with recommendations for reducing risks.

How they work

Steam sterilizers use pressurized steam to generate moist heat to eliminate viable microbes from non-heat-sensitive medical devices and products used for surgical and general patient care. Most tabletop sterilizers have chamber sizes ≤0.015 m3 as well as their own integral steam generators. They are typically used within the hospital in operating suites and labor and delivery areas, in physician offices, and outpatient medical-surgical facilities.

Items to be sterilized are cleaned to remove contaminants and rinsed with distilled or de-mineralized water to remove any detergent or tap water residues. They are put into packs and loaded into baskets that are placed in the chamber. The chamber is closed, and the appropriate time and temperature settings are selected. Some sterilizers allow these parameters to be preset so that the push of a button will start sterilization.

When steam enters the sterilizer chamber, it contacts the cool outer layer of the wrapped pack and condenses on it, leaving behind a small amount of water and transferring substantial heat to the fabric. The condensation also causes a 99.9% decrease in its volume and pulls in more steam to replace what has changed to water. The steam condenses on the next layer inward. The process continues until the steam has heated all items within the pack. Once heated to the selected sterilization temperature, the packs are held at that temperature for a preset length of time. The higher the temperature, the less time needed to achieve sterilization; the typical temperature range is 121° to 135°C (250° to 275°F). After the sterilization cycle is complete, the steam is exhausted with the aid of a partial vacuum, and the sterile items are dried using radiant heat from the chamber and the evaporative effect of the vacuum.

Air elimination methods

Air acts as a barrier against the penetration of steam into a pack and therefore must be removed from the sterilizer chamber by gravity, vacuum, or a combination of gravity and vacuum.

Gravity method—With this method, used by most tabletop steam sterilizers, steam rises above the cooler, heavier air in the chamber and gradually forces that air out through a steam trap at the bottom of the chamber.

A major disadvantage of gravity units is the long cycle time required for adequate steam penetration and effective air elimination from the chamber. The lower sterilization temperature also requires a relatively long period of exposure. Total cycle time for a gravity sterilizer can exceed one hour.

Vacuum sterilizers (also called pre-vacuum or high-vacuum sterilizers) provide quicker and more effective air elimination from the chamber than do gravity units. At the beginning of the cycle, steam is injected at the same time that a partial vacuum is created (preconditioning), rapidly pulling the air out and the steam in and permitting the load to be heated very quickly to the selected temperature.

Immediate-use sterilization, also known as flash sterilization, is used to quickly sterilize instruments that have become contaminated during surgery and need to be reused. This rapid sterilization process does not use full cycles of exposure and drying times. Exposure cycles are shortened by eliminating wrapping material or using sterilization containers to ensure that all instruments are concurrently exposed to the steam. The Association for the Advancement of Medical Instrumentation (AAMI) has issued the following recommendations for immediate-use sterilization:

• Use only when the sterilized items are urgently needed and no spare sterile items are available.
• Follow proper procedures before sterilization, such as cleaning, decontaminating, and inspecting instruments and properly arranging items in the container or tray.
• Position the sterilizer close to the point of instrument use.
• Develop procedures to ensure proper aseptic instrument handling and safety during the transfer of sterilized items.

Reported Problems

The most notable problem is...

To read this complete article from TechNation's August 2012 issue click here.