Effective sterilisation of used instruments to prevent transmission of microorganisms depends on temperature, pressure and time – each of these parameters needs to be monitored.
The sterilisation cycle is monitored by multiple methods:
- mechanical/physical/electronic indicators recorded by automatic printout or computerised data logger – need to be checked for every cycle before the load contents are released for use
- chemical indicators – included with every pack/pouch and load, and placed on each tray containing unwrapped items
- biological/enzymatic indicators – used during validation and when steriliser operation needs to be rechecked.
All sterilisers need to automatically generate recorded data.
Mechanical/physical/electronic monitoring
Sterilisers need to be fitted with devices (gauges/timers/digital readout) that provide visible evidence of the time, temperature and pressure during a cycle.
Results are automatically recorded by printout or a data log, which needs to be viewed after each cycle before sterilised items can be released for use. The printout or data logger shows the temperature and pressure at critical points during the sterilisation cycle as well as the drying time.
Chemical indicator monitoring
Classes of chemical indicators
- There are six classes (Class 1–6). See Table 10.24 for types of chemical indicators.
- Higher classes provide more specific information about the sterilisation process.
Required use
- Class 1 chemical indicators need to be used on:
- every pack in every load, or
- the tray of unwrapped items.
- Self-sealing pouches and some sealing tapes already include Class 1 indicators.
Optional use
- Other classes of chemical indicators may be used to:
- Detect suspected faults.
- Provide additional process information.
Timing
- Check colour change immediately after unloading the steriliser.
- Colour changes after storage do not provide evidence of effective sterilisation.
Documentation
- All chemical indicator monitoring need to be recorded.
Table 10.24 Types of chemical indicators used in general practice
|
Class
|
Description
|
When used
|
Cycle type*
|
Advantages
|
Disadvantages
|
|
1
|
Process indicator (eg steriliser indicator tape)
|
On every pack in every load
On the tray of every unpacked load
|
All classes
|
Can assist in easily distinguishing between processed and unprocessed loads
|
Designed to reach their endpoint after an exposure to a cycle that may be less than adequate for sterilisation
|
|
2
|
Specific test indicator (eg Bowie–Dick-type tests)
|
According to practice risk assessment
|
Class B
|
Designed to show air removal and the rapid and even penetration of steam
|
Designed to reach their endpoint after an exposure to a cycle that may be less than adequate for sterilisation
|
|
6
|
Emulating indicators (eg 134°C for 3.5 minutes in steam under pressure)
|
Assurance that all critical conditions of the sterilisation cycle are met, based on the settings of the selected sterilisation cycles
|
All classes
|
Provide a very high level of assurance that all critical sterilisation cycle parameters are met. They are useful when cycle printouts or validation documentation are unavailable, such as during emergency use, with loaned or newly installed sterilisers pending validation, or in immediate-use sterilisation scenarios.
|
Failure may not identify which specific parameter/s have failed
|
*Steriliser type or cycle class of steam steriliser
Note Class 3 indicators (indicators for a single parameter) are no longer used. Class 4 and 5 indicators are generally not used in general practice (if needed, refer to AS 5369 – Reprocessing of reusable medical devices and other devices in health and non-health related facilities for further guidance on their use).