Sterilization: Parameters, Monitoring, and Release
What you must understand
Sterilization destroys all microbial life, including spores, and depends on the right combination of temperature, pressure, time, humidity, and load configuration. Know the main modalities: steam (gravity displacement and prevacuum), ethylene oxide, hydrogen peroxide plasma, dry heat, and ozone, plus liquid chemical sterilants for specific devices. Each method has compatible packaging, load limits, and aeration or residual requirements.
Monitoring has three levels. Physical monitoring reads gauges, printouts, and charts. Chemical indicators change with exposure and are placed outside and, where required, inside packages. Biological indicators contain known spores and provide the closest proof of lethality. Know the standard organisms: Geobacillus stearothermophilus for steam and hydrogen peroxide, Bacillus atrophaeus for ethylene oxide and dry heat. A Bowie-Dick test evaluates prevacuum sterilizer air removal and is not a biological indicator; it is run on an empty chamber.
Release rules matter. Implant loads are quarantined until the biological indicator is negative. If a biological indicator is positive, recall loads back to the last negative indicator, notify the proper people, and follow the facility's recall policy.
Traps that appear in questions
- Releasing an implant load before biological results.
- Treating a Bowie-Dick pass as proof of sterilization.
- Mixing incompatible materials or overloading the chamber.
- Assuming ethylene oxide loads need no aeration.
- Confusing immediate-use steam sterilization with routine processing.
Worked example
A positive biological indicator appears on today's load. The correct action is to recall all loads processed since the last negative biological indicator, not only the current load, and to document the event.
Rule of thumb
When monitoring results are unclear or conflicting, do not release the load.