Drying is a Critical Phase of the Sterilization Process

By Nancy Chobin, RN, AAS, ACSP, CSPM, CFER

Q: We have a dynamic-air removal sterilizer. The load was set for 4 minutes at 270 degrees F. (132 degrees C.) I came back from my break and mistakenly unlocked the door at a few minutes into the exhaust phase. The printout read “aborted." I kept the door shut for a few minutes more, and then opened it about a foot. I kept the load in the sterilizer for about one and a half hours prior to taking it out. Is the load sterile and/or does it have to be re-sterilized?

A:  The steps in processing include transporting soiled, cleaning, packaging, sterilization, drying and storage/distribution. Drying is a critical phase of the sterilization process. Let’s examine why. If packages are still moist when the sterilizer door is opened, bacteria can land on the packages and “wick” or travel inside the package, especially if the packages are handled before completely cooled. Drying time depends on several factors:
· The device manufacturer’s instructions
· The sterilizer manufacturer’s instructions
· The age of the sterilizer
· The packaging system used (e.g., drying time is typically longer for containerized items than
   for wrapped items)
· The weight and configuration of the sets
· The total metal mass weight of the load
· The loading configuration of the sterilizer
· The steam quality
· The environmental conditions within the processing area (temperature and humidity) 

In a dynamic-air removal steam sterilizer, the drying takes place in HEPA-filtered air. In a gravity-displacement sterilizer, drying takes place by evaporation resulting from the heat in the chamber walls and is thus much less efficient.

At the end of the sterilization cycle, if a package is noted to have moisture on the outside of the pack, the package should be completely re-processed.

Consideration should be given to opening other packs in the questionable load to check for moisture and/or to recalling all items from the load. “Damp” or wet packs should never be placed back inside the sterilizer to “continue to dry.”

Handling wet packs can cause microorganisms to migrate inside the package, contaminating the contents.  These recommendations apply to boiler type sterilizers.

Wet pack at the end of a sterilization cycle

However, if the dry time set for the cycle was not completed, then you have no proof that the load contents were, indeed dry.  They may look dry on the outside of the packaging but may still contain moisture inside, which is not visible in a wrapped package or rigid container.

Moisture inside wrapped set

Drying in table-top sterilizers (generally gravity displacement type) is usually achieved by cracking the sterilizer door (to release the steam inside the chamber) and running the drying cycle. The sterilizer manufacturer’s instructions should be followed carefully. The sterilizer should not be located in a high-traffic area or near an air conditioner or air vent; otherwise, condensation could form. The sterilizer manufacturer’s drying instructions should be followed; the typical recommendation is to open the door approximately one-half inch (1.25 cm) at the end of the cycle to allow moisture to escape and then initiate the drying cycle, which usually operates with the door open. A drying time of at least 10 minutes is usually recommended. If the sterilizer does not have a drying cycle, the manufacturer’s instructions on how to dry the load should be consulted. Processed items should be visibly dry when they are removed from the sterilizer. Today, there are tabletop sterilizers that permit drying with the door closed.

Another concern is that the printout indicated the cycle was aborted yet it was released. AAMI ST-79 (2013, section 10.5.1) states, “At the end of the cycle and before items are removed from the sterilizer, the operator should examine and interpret the chart or printout to verify that all cycle parameters were met and initial it to permit later identification of the operator. Sterilizers that do not have recording devices should not be used.” Therefore, since the cycle was aborted and all the parameters were not met, this load should not have been released.  Instead, all of the items should have been reprocessed. Remember, the printout can be a legal document and if subpoenaed in a court of law, you would have to justify why you released a load that aborted and did not meet all the stated parameters, including dry time.

In summary, whenever a sterilization process abort/failure occurs, you should notify your supervisor and document the problem and all the action(s) taken.  Mistakes are made but as long as we own up to and correct them, we do not put the patient’s safety at risk. Always err on the side of caution and never assume. This was a learning experience for you and your wo-workers and in the future, you will know how to handle such issues.

Nancy Chobin, RN, AAS, ACSP, CSPM, CFER, is a sterile processing consultant and educator.