The possible reasons for failure of a Steam cycle are:
Incomplete air removal
Poor quality steam
Inadequate cycle temperature
Insufficient time at temperature
Incorrect choice of packaging
Improper packaging technique
Improper loading technique
The possible reasons for failure of an ETO cycle are:
Low gas concentration
Goods too dry
Improper packaging material
All standards and required practices call for using internal chemical indicators, biological indicators, external indicators and the physical monitors (i.e. printout) to monitor sterilization. Each of them gives different information about the process, and it's necessary to use them all in order to get a complete picture of what's taking place. Class 5 integrators are not "better" than biological indicators. Each fills a need and gives different information.
Class 5 integrators are designed by manufacturers to equal or exceed the performance requirements of biological indicators. It's essentially a manufacturer's best attempt to mimic a microorganism. However, microorganisms are very complex and it's not possible to exactly replicate what microorganisms do. We can model them in a sterilization process and say that they are dead after 16.5 minutes at 121 degrees C and 2 minutes at 132 degrees C, then design an indicator that visibly changes at those conditions. That's why the language is to equal or exceed performance requirements of biological indicators. However, that's not the same as microorganisms - they're more complex than 3 data points on a chart in a specific range of temperatures.
Biological indicators contain living microorganisms. The entire point of sterilization is killing microbes, so using a tool that contains them is the best way to determine that sterilization worked. Chemicals work well and can give very similar results, but they're just not the same. Many would say that biological indicators are the most critical test for sterilization. You can design a chemical to meet performance requirements (those 3 points on a chart) but that's not what a microorganism or biological indicator is.
Note that chemical indicators are still very good and very important because they're the only indicators beside medical devices - they tell you what's happening inside each pack. But they're not the same as biological indicators and they can't replace them.
You should annually qualify the cycles that you're using for each sterilizer. If you will never use a gravity cycle, I suppose there's no need to qualify it. However, if there is a chance to do it even once then it should be qualified. If you think you won't use a cycle, you could remove it from the presets or make a note on the sterilizers that Cycle XX is not qualified. The qualification is intended for temperature/air-removal combinations - there's no need to qualify longer exposure times.
We recommend the following:
The Attest 1262 biological indicator. It has a 48 hour readout time (i.e. final results in 48 hours), the Comply 1243 SteriGage chemical indicator. It is designed to correlate to the response of a biological indicator – I call it a manufacturer’s best attempt to mimic a microorganism. Alternatively, the Comply 1250 chemical indicator will work, however it gives less information about the sterilization process. We also recommend peel pouches for your practice. By placing your instruments in peel pouches, it will prevent contamination between sterilization and use on patients. All current recommendations are to use some form of wrapping material to prevent contamination before the device is used.
It is recommended to let a BI cool to room temperature after sterilization regardless of the type of test pack/PCD (e.g. commercial, in-house, or those used for performance qualification) before activating. Hot BIs have a hot liquid media ampoule inside that is under pressure due to the elevated temperature during and after sterilization. The reason BIs should be cooled is so that the ampoule containing the liquid is at or close to room temperature, not pressurized, and will not pose a risk to the user when activated.
Specifically for performance qualification, it is still necessary to let the BI cool but the entire set does not need to be cool before opening it. Because the set will not be used, there is no concern about contamination – it will be opened in the CSSD anyway. You may open the set and remove the BI for 10 minutes to cool so that the ampoule containing liquid is no longer under pressure and can be safely activated.
There are 3 common detection methods for Biological Indicators (BIs).
Numbers 2 and 3, the two most common methods, both rely on detecting by-products from bacteria; one uses acidic waste and the other uses a marker released when food is consumed. They both accurately measure bacterial activity, but the fluorescence marker BIs do so much quicker because the detection method is much more sensitive and requires fewer by-products to register a positive.
Please follow hospital policy. For negative BI, hospital can dispose as normal waste. For positive BI and control BI with positive result, please dispose as medical waste which needs to be sterilized again (132-134C, 4 minutes) and disposed as normal waste post sterilization.
A positive biological indicator suggests that the Sterilizer conditions were not sufficient to kill microorganisms and that the sterilization cycle failed. Unless there is evidence that points to human error or some other cause not related to the sterilization cycle to produce a positive biological indicator test result, it should be assumed that the load is not sterile.
Those loads should be reprocessed (cleaned if necessary, repackaged, and re-sterilized).
The cause of the failure should be investigated and corrected. Once that is done, the sterilizer should be tested to confirm it is in working order using 3 consecutive BI tests and 3 Bowie-Dick tests (6 cycles in total) to confirm that the sterilizer is working as per the requirement. Once that is complete, loads may be processed as normal.
A control biological indicator verifies the following:
A control BI shows that the entire Auto-Reader incubation system is working and will detect positive BIs.
Steam must come in contact with surfaces in order to sterilize; air acts as an insulator that prevents contact of steam with surfaces so it must be removed at the beginning of a steam sterilization cycle. The Bowie-Dick test is used to verify that air removal and steam penetration in pre-vacuum steam sterilization cycles is efficient (also referred to as an air-removal test, or a steam penetration test). It is only used in pre-vacuum steam sterilization cycles, not gravity or pressure-pulse air-removal steam cycles, and not for chemical sterilization processes.
The Bowie-Dick test consists of a test sheet in a PCD with heavy paper sheets or a towel pack as suggested by AAMI, and is used in an otherwise empty chamber. If air is completely removed at the beginning of a cycle, when steam enters the chamber it will penetrate the pack, reach the chemical indicator in the Bowie-Dick test pack, and completely change the indicator lines from yellow to black. This shows that air-removal and steam penetration was efficient.
If there is some air left in the chamber at the beginning of a cycle, it will be trapped in the hardest to remove location – in the test pack. When steam enters, it will reach throughout the chamber and the edges of the test pack, however it won’t penetrate past the air bubble in the middle of the test pack; the indicator lines on the edges will change color but there will be a spot in the middle that doesn’t change color (the yellow spot in the middle “shows” the observer air). This is a test failure because it shows that air-removal and steam penetration is not sufficient.
The short answer is that the Bowie-Dick test is the only form of consumable equipment control and only for pre-vacuum steam sterilizers. The long answer is that there are 2 aspects to equipment control: physical monitors on all sterilizers and the Bowie-Dick test for steam sterilizers.
Physical monitors (aka monitors of physical parameters) are built into the sterilizer and are an integral part of sterilizer. On steam sterilizers, they are thermometers, pressure gauges, and timers. Chemical sterilizers additionally may have humidity sensors or sterilant sensors. Monitors of physical parameters are used every cycle to verify that the sterilizer is working properly and the records are kept by the facilities.
The Bowie-Dick test (aka air-removal test or steam penetration test or ISO Class 2 Special test) is only used for pre-vacuum steam sterilizers. It's required once per day for each sterilizer. The Bowie-Dick test is an extra one just for steam sterilizers, and it's probably unique because steam typically comes from a distant boiler and the quality is less controlled than for chemical sterilizers with a chemical sterilant supply directly within the sterilizer. For example, if there's an air leak in the steam supply line, the time, temperature, and pressure would read as expected; it would only be the Bowie-Dick test and possibly the other indicators that would pick up that issue. Because chemical sterilizers are more controlled with a commercial supply of sterilant and integrated piping, it's less likely that there would be an issue.
Air is removed in both cycles but it is removed more efficiently in a pre-vacuum cycle. An effective test for a pre-vacuum cycle must be challenging, and it would be more challenging than a typical gravity cycle would pass. There are some gravity or pressure-pulse cycles that claim to pass a Bowie-Dick test, but not all are that efficient. Also, the Bowie-Dick validated test conditions are 3.5-4 minutes at 132-134°C (pre-vacuum cycle), which are not common for a typical gravity cycle.
In a gravity cycle, it’s very important to ensure that packs/sets are loaded correctly so that air is removed efficiently. Biological and chemical indicators tests will fail if there is a process failure, but there isn’t a great way to check that air was removed in a gravity steam sterilization cycle.
Let’s use a roller coaster analogy when describing the change:
You're in line at an amusement park and as you're watching a roller coaster go around, it flies off the track; that's a failed ride. The attendant says "wait, wait, let me run another one around." It goes around the track without issue (a successful trip), pulls in front of the line, and the attendant opens the door and asks you to get on. Do you get on that roller coaster? The last trip worked fine, so why be concerned about the first trip that failed? Essentially you've got one failure and one pass, and you should assume that things are fine now?
Everything in reprocessing is about handling issues like it's the worst case scenario, with a better safe than sorry attitude. It made no sense to have this outlier. The US AAMI document has the same requirement of recall on the first failure, for both BIs and Bowie-Dick tests.
You can shut down the sterilizer, have it looked over, then run operational qualification to get back up and useable. If this is a concern, there are 2 things you can consider: use the 3M 00135LF Bowie-Dick test pack with an early warning sheet - it should detect issues before the official Bowie-Dick sheet fails (provided it's a degradation issue and not random bits of air in the steam supply). Alternatively, you can run a BI in the last load of your day so that any recall from a failed Bowie-Dick test only goes back to that load with a BI.
Steam sterilisation specifies that every sterilized pack must have an internal chemical indicator. If there is a multi-level set, an internal chemical indicator must be placed on each level.
For loads that are not monitored with a biological indicator (i.e. for those loads that only use chemical indicators and monitors of physical parameters), the internal chemical indicators must be either an ISO Class 5 or Class 6 chemical indicator. Loads that are monitored with a biological indicator can use any class of internal chemical indicator inside each pack, for example Class 4, Class 5, or Class 6. This new requirement ensures that every pack is monitored by a tool that assesses all the critical variables, whether it’s a biological indicator or Class 5 or 6 chemical indicator.
A pressure-pulse air-removal cycle is an efficient means of removing air that is usually found in table-top sterilizers. It works by adding steam to the sterilizer so that it is pressurized, then releases the pressure so that air moves out of the sterilizer; when this type of pressurization and release cycle is done multiple times, air is effectively removed from the sterilizer.
Pressure-pulse air-removal cycles are more efficient than a gravity displacement cycle that simply introduces steam at the top and pushes air out through a drain at the bottom of the chamber. The pressure-pulse air-removal cycle does not go below atmospheric pressure (i.e. does not draw a vacuum), so it is a different process than a typical hospital sterilizer that uses a pre-vacuum steam sterilization cycle.
The same forms of monitoring are required: biological indicators, and internal and external chemical indicators.
An IUSS (Immediate Use Steam Sterilization) or “flash” cycle is for emergency sterilization of medical devices. It is supposed to be avoided at all costs and should only be used when there is an urgent unplanned need for the device (e.g. for a device needed in a trauma-related event that will save a patient’s life or limb). It is often done in the OR area of the hospital, although many hospitals also have the IUSS sterilizer in the CSSD.
Historically, typical conditions are a 132 or 135 degree Celsius gravity cycle; the BIs for this cycle are the 1491, 1291, or 1261. More recent sterilizers may have a pre-vacuum cycle at 132 or 135 degrees Celsius; the BIs for this cycle are 1492V, 1292, and 1262.
The concept behind enzyme detergent instrument cleaners is quite sound. All enzymes are proteins created within a cell to ensure the growth and development of the cell.
Each enzyme is a different protein and has a specific biochemical function, which is the synthesis or digestion of natural molecules. It is currently estimated that there are between 2,500 and 3,000 different enzymes in the human body, each with its specific function. Every enzyme has uniquely shaped active sites. The shape of this active site precisely matches the shape of some part or parts of its corresponding biological molecule.
In the early days of enzymatic instrument cleaner’s only proteases, the enzymes which digest proteins, were incorporated into the detergent-based formulations. These products proved to be more efficacious than detergents alone. However within a few years it became clear that this was not a total solution to the problem as the contaminating protein was often mixed with mucous, saliva, fats, etc. and the proteases were not able to digest these non-proteinaceous materials and, thus, not gain contact with the contaminating soils. Total multi-enzyme products can digest all of the biological contaminants.
For this reason, there has been a significant effort amongst researchers to arrive at formulations which incorporate all of the enzymes necessary to digest the full spectrum of biological contaminants. Such formulations which include surfactants, come into contact with dirty instruments, resulting in digestion of the biological materials, which ensures the effective rinsing away of the digested molecules. The better enzymatic cleaners contain surface tension depressants, which ensure the penetration of the liquid into even minute cracks and crevices, which can otherwise be isolated from the liquid by the formation of a bubble over the surface of the imperfection.
This objective of stable, full enzyme spectrum cleaners has only recently been achieved as the technical challenge was very significant. The core of this challenge related to the stability of enzyme activity. Whilst enzymes are not "alive" their chemical activity is somewhat fragile and the activity of each enzyme species tends to be irreversibly destroyed by other enzymes. Once the activity of any enzyme is lost, its ability to influence biochemical reactions is lost and its presence is redundant.
The function/action of enzymatic cleaners and detergent is very different. — requires pre-cleaning to remove gross soiling, then the item is Enzymatic Cleaners soaked for the appropriate time. The enzymes do all the work, by breaking down and digesting any biological debris left on the item, they will penetrate all of the most challenging areas, ie, box and hinge joints, serrated teeth/edges etc. allowing any remaining loosened debris to be rinsed away.
Detergents — require an automated or manual element of cleaning, with brushes etc, to loosen and remove the debris (manual cleaning). The difficulty with manual cleaning, is that brushes cannot get into all the challenging areas on instruments, and the person doing the cleaning can be exposed to the risks of aerosols and 'flicking debris' through the bristles of the brushes flicking off the instrument surface.
Generally detergents cannot clean an item as thoroughly as a MULTI-enzyme cleaner.