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Sherlock Holmes' Approach to BIs & CIs
By Martha Young, BS, MS, CSPDT
The mission of a department producing sterile medical devices is to improve theproducts and services provided continually and meet the changing requirements of thecustomer while ensuring that products are safe for patient use. The results of chemicaland biological indicators (CIs and BIs), in addition to mechanical monitors andinformation included in record keeping, are used to detect failures in the sterilizationprocess. When failures are detected, the next step is to try and determine the cause ofthe sterilization process failure.
Pay attention to the clues provided by the BIs and CIs and mechanical monitors to seeif you can solve the problem as Sherlock Holmes and Dr. Watson work through thesesituations.
A rapid readout BI and a chemical integrating indicator, commonly referred to as achemical integrator, were run inside each sterilization container system. The containersystems were routinely processed for 10 minutes in the 270Â°F/132Â°C gravity steamsterilizers. Sporadic positive BIs, detected after one hour of incubation, startedoccurring. The term sporadic positive BIs is used because not every BI from everycontainer in every sterilizer is positive. Sometimes the BIs are negative and sometimesthey are positive. This is an indication of a marginal sterilization process. In allcases, the CIs showed an accept. Why are the CIs showing an accept but the BIs are notalways killed inside the container?
Sherlock Holmes discusses the situation with Dr. Watson:
The investigation revealed the answers to the above questions:
Conclusion: The defective valve on the container system was detected by thepositive rapid-readout BIs but not by the chemical integrators. This is because the sporesof the BI are sensitive to small changes in the sterilization process. Spores are used inBIs to test the efficacy of the sterilization process because they die at a very slow rateand because they are affected by the same kinds of changes in cycle conditions that wouldeffect the microorganisms commonly found on the items being sterilized.3
CIs designed around the "biological" view provide information aboutcombinations of process parameters, such as temperature and time, but they may not detectsmall (but potentially significant) deficiencies in individual parameters.3 BIsintegrate all the parameters of the sterilization process to ensure that adequateconditions are present during the process. CIs should still be used inside each package todetermine that the sterilant has penetrated the package and should be used in conjunctionwith BIs to determine the effectiveness of the sterilization process.4,5,6
This situation required additional testing with BIs and CIs because the positives wereoccurring sporadically, and it was not immediately evident whether the problem was withthe sterilizers, steam quality, or the container systems. Testing each container systemwith BIs and CIs in one sterilizer isolated the problem and identified the defectivecontainer systems.
The container systems were repaired and tested with BIs and CIs according to the AAMIrecommended practices to determine that the container systems were working before theywere put back into routine use.1,2
This hospital continues to use a rapid-readout BI in every load in the Operating Roomand in Central Supply because they feel that only a biological indicator can tell thewhole story. A chemical integrator is also run in each container. The Central Supplymanager stated that "with a chemical integrator you know what sterilizationconditions existed in the pack, but you don't have the assurance of knowing positivelythat the bacteria were killed."
A disposable rapid-readout biological indicator steam test pack was run in the firstload of the day and with each load containing implantable medical devices in all steamsterilizers in Central Processing. The BI results indicated sporadic positives from onesterilizer. That sterilizer was an older-model, vacuum-assisted steam sterilizer that rana 270Â°F/132Â°C 4-minute cycle. The Bowie-Dick test always showed a pass, and themechanical monitors indicated that the correct cycle parameters were being met. All thechemical integrators inside the packages showed an accept.
Sherlock Holmes and Dr. Watson sat down for tea to discuss this situation:
Since the positive BI occurred only in one sterilizer, the discussion centered on thatsterilizer.
The investigation revealed the answers to the above questions.
Conclusion: Since there was only one sterilizer showing positive BIs, theproblem had to be related to the sterilizer, steam quality, or how that sterilizer wasused. A steam quality problem was finally detected by the sterilizer repair person.
The sterilizer was repaired to correct the steam quality problem. Sterilizer efficacytesting was performed according to the AAMI recommended practices.4 Adisposable rapid-readout BI steam test pack was run in three consecutive empty loads.After the rapid readout, BIs were negative, the CIs reached their appropriate endpointresponse, and the sterilizer was put back into routine use.
As in situation one, the BI detected a problem while the chemical integrator did not.According to Dr. Jack Young, this is because the BI is more sensitive at detecting steamquality problems than a CI.7 This situation is an excellent example of the needto use both BIs and CIs to monitor the sterilization process. Running BIs in each loaddetects sporadic changes in the sterilization process.
This hospital now runs rapid-readout BIs in each load and chemical integrators in eachpackage. From the hospital viewpoint, the side-by-side double check of tandem chemical andbiological monitoring is the safest and wisest way to go.
The Central Service technician checked to see why the 270Â°F/132Â°C vacuum-assistedsterilization cycle was taking so long. The technician looked at the mechanical gauges andprintouts and noticed that the sterilizer had been in the "come-up mode" for thepast hour. The sterilizer never switched to the sterilization mode. The technician turnedthe sterilizer off and removed the load. The rapid-readout BIs from the disposablerapid-readout steam pack from the load were incubated, and the results were negative afterthree hours of incubation. The load was broken down, and all the chemical integratorsinside the packs showed a reject. The load was repackaged and re-sterilized.
Sherlock Holmes and Dr. Watson discussed this situation while playing darts at thelocal pub.
The investigation revealed the answers:
Conclusion: The sterilizer was repaired, re-tested, and put back into routineuse. This is an example of why the results of all process monitoring controls must be readand interpreted to determine the efficacy of the sterilization process. Each of thesemonitors/indicators measures parameters of the sterilization process in differentlocations and by different methods. The results of the BI showed that the cycle had enoughtime and temperature in the presence of steam to kill spores even if the requiredsterilization parameters were not met as indicated by the mechanical monitor and thechemical integrators. This load would not be used because all the quality control checksdid not indicate that the sterilization process was acceptable.
The Operating Room opened a package containing a scope and found an ethylene oxide (EO)internal CI with an incomplete endpoint color response. The package was returned toCentral Service for reprocessing. Sherlock Holmes thought about this situation:
The investigation revealed:
Conclusion: For effective EO sterilization, you need adequate humidity in theprocessing area, inside the chamber, and the packages for EO to penetrate and effectivelykill spores. In this situation, the packaging used for the scope was too absorbent and thelow relative humidity in the processing area aggravated the situation. Whenever majorchanges are made in packaging, wraps, or load configurations that include the addition ofa new type of package or tray such as this scope example, product testing, in accordancewith AAMI recommended practices, must be done to ensure that the product change can besterilized effectively.4
This problem was detected by the internal CI because it was inside a package that wastoo dense. If an internal CI is not used inside each package, this problem could goundetected, and a non-sterile scope would be used repeatedly on patients.
If you did not solve the problems, review the following tips and start thinking likeSherlock Holmes and Dr. Watson when you have a sterilization process failure.
Tips for Problem Solving:
Use common sense and your knowledge of the sterilization process to determine what theclues are telling you. Don't be frustrated if you cannot determine the problem. Sometimestransient situations occur that disappear before they can be identified. With practice andby asking the right questions, you will get better at solving the problems. If all elsefails, have a cup of tea or play some darts and see if new thoughts cross your mind. Thatis what Sherlock Holmes and Dr. Watson did. Good luck.
Martha Young, BS, MS, CSPDT, is an international technical service specialist,Sterilization Products, for 3M Health Care (St. Paul, Minn). She has more than 20 years ofexperience playing Sherlock Holmes and solving sterilization process problems.
For references and Best Practices continuing education application form, see the ICTWeb site.
Test Questions, True or False:
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