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Good day,
I am going to assume that we are discussing hospital sterilizers that have already passed the qualification tests performed by the manufacturer.
A single biological test is all that is required (per AAMI); regardless of whether the sterilizer can hold two or twenty large surgical instrument trays. The biological test should be placed in the area least favorable to sterilization. This point varies with the design of the sterilizer. Typically, in a steam sterilizer, this point is in the front and bottom of the sterilizer, immediately above the drain. In an Ethylene Oxide sterilizer, this point is typically the center of the load. In a Sterrad H2O2 plasma sterilizer, this is the bottom rear portion of the chamber.
Steam sterilization needs to be monitored with a Biological test at least once a week, and in each cycle that contains implantable devices. (I fully expect that someone with a properly validated steam sterilization process will respond to this posting stating that the biological testing is not needed at all for steam sterilization. Please explain the steps required to have a properly validated steam sterilization process!)
Ethylene Oxide and Sterrad H2O2 plasma sterilization need to be monitored with biological indicators in each and every cycle run. This is because there are many variables (such as humidity) that cannot be monitored easily by meters in Ethylene Oxide and Sterrad H2O2 plasma sterilization.
After maintenance has been performed on a sterilizer, one should run at least three cycles with biological tests that indicate 100% kill before putting the sterilizer back into service.
On an editorial note: I am a firm believer in using dye pellet chemical integrators such as 3M or Propper manufacture for monitoring steam sterilization. These are similar in use to chemical indicators, but they measure temperature, presence of steam, and length of time of exposure to steam. They 'integrate' all three of these functions. The pass mark parallels the death curve of one million bacillus stearothermophillus. They predict the final results of biological tests with over 99.99% accuracy. They provide a graduated reading. The graduated reading allows one to monitor the effectiveness of the steam sterilization process. For example; if the integrator normally reads off the top of the graph, way past the 'Pass' mark, but then in later cycles, the graph starts to creep back towards the 'Pass' mark, one knows the effectiveness of the sterilizer is decreasing. The properly cleaned items are sterile so long as the graph passes the 'Pass' mark, but one knows to call for maintenance before the sterilizer fails completely. This is a BIG benefit. Other indicators (chemical or biological) only give a 'Pass' or 'Fail' reading, so you only know if your sterilizer meets minimum standards. They give no advance notice when the sterilizer function is decreasing. Integrators can be put inside each tray and pack to monitor the sterilization process at every point where an item is being sterilized.
Best Regards,
Pete Bobb
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