Chris Miller, PHD
A close look at instrument processing, from start to finish, is called for when developing or reorganizing protocols. Visualize the entire process from the collection of used, contaminated instruments at chairside to opening sterile packages for the next patient. The goal is to deliver sterile instruments to chairside.
A cost factor usually limits the number of sets of instruments available in the office for patient treatment, necessitating a fast turn-around between patients. Even so, there is (almost always) some storage time before processed instruments are used again. Therefore, it is necessary to protect those instruments from re-contamination after removing them from the sterilizer. The steps discussed here are those that will permit sterility to be maintained until the delivery of the processed instruments to chairside.
The first step in this sterility maintenance is to properly package the clean, dry instruments in sterilization pouches (or wraps) or wrapped instrument cassettes before placing them in the sterilizer. Sterility maintenance depends on keeping the packaging material intact until the processed packages are opened at chairside.
Pouches, packs, or wrapped cassettes that have been processed through a dry-heat sterilizer or an unsaturated chemical-vapor sterilizer are dry at the end of the sterilizing cycle. These packages can be cooled and transported to the storage area without delay.
When packages are processed through a steam sterilizer, they are wet at the end of the sterilizing cycle. They should not be handled or removed from the sterilizer until they are dry. Handling wet packages greatly increases the chance for tearing of the packaging material and exposing the package contents to the external, non-sterile environment. Also, exposing wet packages to the air outside of the sterilizer chamber allows the microbes from air and dust particles that settle on the wet packages to be drawn through the packaging material, contaminating the inside of this material and likely the package contents.
Some steam sterilizers have a drying cycle that:
- Draws in air from outside the chamber.
- Filters air through a high-efficiency particulate air (HEPA) filter that removes bacteria.
- Flows air over the packages in the chamber to achieve cooling and drying before the packages are removed from the sterilizer.
In other steam sterilizers the "dry cycle" involves natural drying as the chamber cools, sometimes requiring the chamber door to be slightly ajar to facilitate venting of the moisture and heat.
When unloading a sterilizer after the drying time, it is best to remove the entire tray of items from the chamber rather than to remove one package or "a handful" of packages at a time. Place the tray in an area designated for sterile items (a countertop or a cart, for example) in a low-traffic area out of the direct path of air from vents or air-conditioners. Cool air passing over warm packages may facilitate condensation.
Make sure these packages are not mingled with packages ready to be processed through the sterilizer. The use of chemical indicators on the outside of packages will help prevent the intermingling of processed and unprocessed packages.
After the packages are both dry and cool, they may be gently handled while wearing clean, dry gloves. Perspiration from ungloved hands or moisture from wet gloves can cause localized wet areas and the "wicking through" of microbes on the outer surfaces as mentioned above. Handle the packages as few times as possible. Do not use tongs to manipulate sterile packages for this will likely tear the packaging material, particularly if it`s paper.
If there is a chance for excess dust or moisture contamination of the sterile packages during transport or storage, plastic dust covers may be used over the sterile packages. These covers must not be mistaken by anyone in the office for sterile wrap. Make sure the packages are cool before covering to prevent condensation from forming underneath the cover.
Transport the packages to the storage area. Inspect the packages as they are placed in storage. Re-package and re-process those with torn or wet packaging. Store the sterile packages in dry, enclosed, and low-dust areas away from sources of contamination. Unwanted moisture may come from sinks, floors, open windows, overhead water pipes, outside walls and outside ceilings.
General guidelines suggest that packages be:
- Eight to 10 inches away from the floor.
- At least 18 inches from ceilings.
- Two inches from outside walls.
- Five feet from sinks.
The main problem in storing sterile packages in the operatory, even if they are in drawers, is the greatly enhanced potential for contamination of the packages with spatter, aerosols, and from contaminated hands.
Make sure the storage area is sufficient in size to avoid crushing, bending, or compression of packages. Avoid sliding wrapped cassettes into spaces because protruding nail head or rough surfaces may tear the wrap.
The length of time a sterile package can be stored and still be considered sterile is dependent upon how well the packaging material is maintained. Thus, storage is "event related." An event that may compromise the integrity of the packaging material dictates the storage time.
If packages become torn, punctured, cracked, or wet, their shelf-life is over. Use a "first-in, first-out" rotation of the stored items and inspect each package as it is being retrieved from storage for transport to chairside.
Sometimes the contamination that occurs naturally on the outside of packaging material is a concern in surgery. This is why surgical items often are double-wrapped so the outer contaminated packaging material can be removed just before the package is taken into the surgical facility.
Chris Miller is director of Infection Control Research and Services and professor of oral biology at Indiana University.