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Dear Kas,
I think your question is a great one because "professional judgment" as to when items are "adequately cooled" may vary from one person to the next. This is a great topic for an open discussion that I would like to contribute to. A set standard amount of cooling time for all items at an institution would result in an eye speculum having to wait until the large orthopedic mallet cools before the eye speculum can be released. My professional concerns are preventing condensation and strike-through.
Condensation occurs when warm humid objects are placed on a cool surface. Even items which have been well dried in the autoclave may contain enough steam moisture that sudden cooling can cause dangerous amounts of condensate. The warmer the trays or items, the more total moisture and humidity may still be contained inside the packaging. If warm, humid packages are suddenly cooled (such as by placing them on a room temperature metal shelf), the humidity turns from gas to liquid water, which can cause strike-through and compromise the sterility of the items.
Strike-through occurs when packaging materials are wet. Wet packaging material can not stop microbes on the outside from swimming through the wrapper to the inside of the package. A sterile tray can become contaminated if it is placed on a cool, nonsterile shelf with a damp wrapper, or if the wrapper subsequently becomes wet from condensate.
This contamination after sterilization is what we must prevent to protect patient safety.
So, how cool is "adequately cooled" in my "professional judgment"? This varies with the situation and circumstances. My very first test is to place my wrist on the sterilizer cart. Does the cart itself feel cool on my wrist? If the cart is too hot to touch with my wrist, the items on the cart are certainly too warm to unload. The time to reach the stage where I can comfortably touch the cart with my wrist varies with the type of load. A cart filled with heavy orthopedic instruments will take longer to cool than a cart filled with linens. Heavier loads take longer to cool. Depending on the nature of the load, passing this first stage in evaluating how cool the load is, can take anywhere from 15 to 40 minutes at my institution.
When the cart itself is cool enough to touch with my wrist, I can perform the same "wrist test" on rigid containers on the cart. Because rigid containers have their filters fairly well protected and strike-through can not occur through metal, the rigid containers have the greatest resistance to strike-through. Touching the metal on the outside of a rigid container won't cause strike-through to contaminate the contents of the tray if the tray is still too warm.
Items wrapped in paper or spun material are more likely to suffer from strike-through than items packaged inside rigid containers. These materials can wick water, moisture, and hand oils - especially when the wrapper is still humid from being in the autoclave, leading to microbes swimming through the moist material. Because of this susceptibility, I generally leave wrapped items to cool longer than rigid containers of a similar weight and mass.
I am currently working in the USA, and our linen packs are wrapped in muslin cloth wrappers. The barrier quality of muslin cloth wrappers is so low that these need to stay cooling on the cart for a minimum of two hours before being handled.
Rigid containers have the best resistance to strike-through and can be removed from the autoclave cart sooner than other items. Using some type of insulator between warm and cool items can decrease the chance of a condensate forming. For example, placing a couple layers of towels on a cart and placing the warm item on the towels may prevent condensate from forming if a rigid container packaged tray is needed in an emergency situation. If a rigid container instrument set is going to be used immediately, i.e., the tray is carried from the sterilizer, placed on a ring stand in the OR, and the contents are then transferred directly to the sterile field, the situation is different. I don\'t need to worry about condensate forming a bridge between the sterile contents of the set and the non-sterile world when the warm items are transferred directly to a sterile field. This situation is different than placing a sterilized tray on a non sterile shelf. In this unusual situation where the instruments are going to be placed immediately into the sterile field, I would release the rigid container instrument sets directly to the OR Room as soon as the container is cooled enough to carry with bare hands.
Warm Regards,
Pete Bobb
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