Wet packs in benchtop autoclaves: a common and preventable problem
One of the purposes of sterilisation packaging is to isolate sterilised instruments and devices from the external environment, thereby preventing re-contamination. To avoid re-contamination, packages must be dry when they leave the steriliser after completing the drying cycle and remain intact until the next time the instruments are used.
It is a relatively common problem for 'wet packs' to have moisture on or in the package when it is removed from the autoclave. Moisture may appear as visible moisture, droplets or water stains on or in the pack. If more than one package is wet, the sterilised item is considered to be a 'wet load'. Wet packages are subject to 'wicking' - they allow microorganisms to enter through the package, leading to re-contamination of sterile instruments. Wet packages can also lead to instrument corrosion. Wet packs must be identified and completely reprocessed. Read on to find out more about the many causes of and solutions to wet pack problems.
What causes wet packs?
For benchtop autoclaves, there are two main causes of wet packs - operator error and problems with the autoclave itself. While it may be human nature to assume that faults are usually related to the autoclave, there are many operator errors that can lead to wet packs. Environmental conditions, such as high humidity or low temperatures in the cooling area, can also lead to wet packs.
Operator error
Operator errors that can lead to wet packaging include failure to dry instruments before placing them in the package, sterilization packaging errors, and loading and sterilization errors.
Sterilisation packaging errors include packaging that is too tight or too loose, using incorrect sterilisation packaging, double or double bagging, or using the wrong sterilisation packaging for the purpose, or using packaging or bags that are not specified for the purpose.
Loading errors include improperly stacked packages, overloading/misloading of the autoclave and overly dense packages. Placing packages in a way that prevents air from escaping, placing paper-plastic bags in a position that is not conducive to drying, placing instruments in a position that is not conducive to moisture drainage (e.g. concave instruments and instruments containing a tubular lumen, such as dental drill handpieces) and/or trapping moisture are all causes of wet packages. Unintentional obstruction of the chamber drain can also lead to wet packs. Packages that are too densely packed, have an uneven distribution of metal masses or have heavy metal masses are another reason for the appearance of wet packs.
Sterilisation errors include choosing the wrong autoclave time. Interrupting the drying cycle or selecting a drying time that does not comply with the manufacturer's written instructions for use and is inadequate. In addition, removing the package from the autoclave before the end of the recommended cooling period may cause condensation to form on the package. Packages removed from the autoclave at the end of the cooling period should not be placed on a cool/solid surface as this can also lead to condensation on the package.
Autoclave performance issues
External and internal moisture can occur due to many autoclave performance problems. These include faulty steam line traps, faulty drain check valves, clogged strainers and screens, poorly calibrated pressure gauges, faulty vacuum systems or other steriliser components and damaged gaskets (door seals). Many of these problems can be related to inadequate/lack of steriliser maintenance, which is ultimately operator and facility error as well. If the indicator/printout indicates that sterilization parameters are not being met, or if the drying cycle is shortened/aborted, the sterilized items must be reprocessed. It is worth noting that gravity displacement autoclaves are not as effective at drying instruments as dynamic de-aeration autoclaves. If wet packs occur, a systematic approach must be used to identify errors and problems.
Avoiding wet packs
Each facility must comply with the guidelines, recommendations and regulations relating to the reprocessing of instruments. Equipment used for reprocessing must be labelled with its intended use and validated and tested for compliance in accordance with local regulations. In addition, autoclave accessories are available to position paper and plastic bags and packaging containers at pre-arranged distances and locations to help avoid overloading and misloading.
The manufacturer's instructions for the use of sterilised packaging, sterilisers and the instruments and equipment being sterilised must be followed. These also help to ensure that appropriate materials and processes are used and followed before, during and after sterilisation. Autoclave performance problems can be resolved by following the manufacturer's instructions for use and the requirements for regular testing, maintenance and validation. If performance problems still occur, the equipment manufacturer's service department should be contacted. Operator error may be a one-off error; it may also be related to inadequate training of instrument reprocessors or individuals. This emphasises the need for appropriate training of personnel.
Conclusion
Wet packs are a common problem that can and should be avoided. If a wet pack does occur, the pack must be completely reprocessed. In addition, the cause of the wet pack must be determined and corrective action taken. Successful sterilisation relies on repeatable, standardised steps before, during and after sterilisation, as recommended, guided by instructions for use and regulations.
