Wet Packs and Moisture Issues: Common Causes and Solutions

As the manager of a Sterile Processing Department, there are few issues more frustrating and difficult to easily diagnose than a wet pack complaint from the OR. A wet pack is a wrapped tray or sterile pack of instruments that show evidence of residual moisture after undergoing the sterilization process. A wet pack can be the beginning of a very daunting task because it could mean any of a multitude of errors may have happened during the sterilization process. Below we are going to explore the common causes and solutions.

What are wet packs & why do they occur?

A wet pack occurs when moisture is found on or within a sterilized container or pouch after the sterilization process is complete. This can be a sign that something is wrong with the sterilizer, that there was a mistake in the handling or processing of the load, or that there may be issues with the steam supply or service utilities. During the sterilization process medical equipment is heated with steam and then undergoes a drying process to make sure that any excess moisture is removed from the load. Residual moisture acts as a conduit for microorganisms to contaminate previously sterile equipment and can even harbor microbes, insulating them from the sterilization process. This makes wet packs one of the most concerning issues faced by OR and sterile processing staff.

Common Causes & Solutions

When trying to identify the cause of a wet pack or wet load, the trick is knowing what to look for. 

  • Loading the Sterilizer: SPD (Sterile Processing Department) personnel need to be trained to operate the sterilizers correctly and make sure they are choosing the right settings with the correct drying times to prevent wet packs. This seems like it would be common knowledge but is often overlooked and assumed that the operator already knows what they are doing. One of the biggest problems is how the autoclave or sterilizer is loaded. If the chamber drain is covered or if the steam does not have ample room to travel around the load, the chamber may not drain correctly and steam can condense on the load. 
    • Solutions:
      • Ensure the right cycle is selected
      • Ensure the proper amount of drying time is selected during the cycle
      • Don’t overpack the autoclave
      • Don’t cover the chamber drain
      • Make sure there is room for steam to properly move around the load
  • Load Handling Post Cycle: Once a load has completed it sterilization process and the door to the sterilizer is opened residual moisture can condense on the outside of the load as it cools. Tightly placed or stacked items can trap that moisture and create water spots or puddles. 
    • Solutions:
      • Ensure loads have the proper amount of space around them
      • Don’t stack loads
      • Allow loads to adequately cool before removing them from the sterilizer
      • Make sure you allow for enough aeration time before storing
  • Device Failure: When a component within your autoclave like a valve, steam trap, vacuum system or chamber drain strainer fails it may result in a wet pack or wet load
    • Solutions:
      • Ensure proper maintenance is performed at regular intervals
      • Ensure that the daily, weekly and monthly user-level maintenance procedures are outlined and performed.
      • Perform a daily biological and Bowie Dick test on all steam sterilizers to ensure that steam saturation and vacuum are within parameters
      • Check the tape after every load to ensure that all sterilization parameters for temperature, pressure and vacuum were maintained during the cycle.

Here are a few more common problems and solutions from Purdue Technical Continuing Education for use when identifying the cause of wet packs:

Dense instrument set Steam cannot readily escape
Loading of the sterilizer too tightly Insufficient space for steam to escape after sterilization
Improperly loading the sterilizer so that the metal containers are above peel packs or fabrics Causes condensation to drip onto the lighter items below
Solid flat tray or basins not placed on an angle Prevents steam from escaping
Improperly prepared items that result in concave surfaces in the wrong position, Multi-part instrumentation not disassembled Prevents steam from escaping
Not following medical device IFUs Some IFU require longer dry times
Using the wrong type of packaging material. Using a packaging material not validated for steam sterilization can result in moisture being trapped, leading to a wet pack
Loading peel pouches in the sterilizer flat May not permit steam from escaping
Wet Instrumentation or packaging going into the sterilizer Insufficient drying of instrumentation or packaging before sterilization may leave excess moisture in the set
Wet sterilization containers Check the container IFU to assure the correct sterilization cycle and for loading contents
Pooling on/in a wrapper caused by excess folds Check the wrapper size. If the wrapper is too large for the item being packaged, it may create a pooling area for steam.
Insufficient cooling time allotted for sterilized items Transporting hot items to a cool surface or environment can result in condensation

Bowie-Dick and Biological Tests

Bowie-Dick and biological tests are common diagnostic tests performed on autoclaves and sterilizers to qualify that the processed loads are sterilized, and the device is functioning correctly. For more about diagnostic tests click here.

Best Practices

Preventing wet packs is a manageable task when you develop and follow a regular maintenance schedule. Manufacturers’ recommendations should be followed with a user-level task list as well as a set schedule for annual maintenance. Having a biomedical service technician available when issues arise is also extremely helpful and can avoid a delay in getting the device fixed in a timely manner. 

Contact ERD to schedule your autoclave or sterilizer maintenance. ERD’s biomedical service technicians are factory trained and can help you ensure efficacy, reliability and precision. 

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