SELF-STUDY SERIES
to be taken in these situations, but an inves- tigation into the cause of the failure will always be required. Where do you start? AAMI ST79 provides excellent guidance on how to conduct an investigation (see Figure 10 and Table 4 in the 2017 edition)4
.
While this information is specific to steam sterilization process failures, the principles can be applied to VH2
investigations as well. O2 sterilization failure
Now let’s hear about a couple of real-life positive BI mysteries, and how they were solved . . .
Story 1: BI positives in steam sterilization This story starts with a hospital’s call to a BI manufacturer’s technical support team reporting a single positive BI from one of their four sterilizers. Their SPD is very busy with all four sterilizers running mul- tiple cycles each day, and they only experi- enced this single positive BI. Their facility monitors every steam load with a BI/ PCD. The hospital reported that the cycle printout from the failed process looked fine, and all the chemical indicators in the load showed ‘pass’ results. They had called their sterilizer sales representative to ask for help, but the sales rep simply referred them to the BI manufacturer, suggesting that perhaps this was a defective BI. The BI manufacturer’s technical team reviewed some history. This hospital had experienced several positive BIs from multiple sterilizers two years earlier that had been traced to poor steam quality sup- plied to the department. The hospital had invested in a dedicated steam supply for the sterilizers, which solved the problem. The tech team confirmed that the BI was not defective and felt the BI had detected a problem with that cycle, but it was not possible at that point to determine the exact cause of the failure.
A couple of weeks passed, and the hos- pital called again. They were now getting more positive BIs from the same sterilizer. The BI manufacturer suggested that the hospital request a service call by the steril- izer manufacturer. During the service visit, the service representative noted that this sterilizer was due for maintenance, and he had also seen signs of minor cracks in the door gasket during an earlier visit. He replaced the door gasket, and the positive BI problem was solved. What are some of the learnings here?
Steam quality is the most common cause of steam sterilization process failures, and BIs are uniquely able to detect these problems. Steam quality problems can start slowly
Sponsored by
and produce intermittent failures, making it appear that the BI is inconsistent instead of the process itself. In this case, the fact that only one of four sterilizers had a problem meant that the steam supply was not the root cause. The sterilizer with the positives did, however, had a maintenance issue specific to that one sterilizer. The faulty door gasket allowed air into the chamber, compromising the steam quality inside the chamber, resulting in positive BIs. Finally, every load monitoring provided more data and made it much easier to understand and define the scope of the problem. Now, let’s move on to a VH2
O2 story. Story 2: BI positives in VH2 O2 sterilization
This time the call to the BI manufacturer’s technical support team was about inter- mittent BI positives in a hospital’s ASP STERRAD 100NX sterilizer. This sterilizer can run four different sterilization cycles (Standard, EXPRESS, Flex, and DUO), however, the positive BIs only occurred in DUO cycles. The BI tech support team trav- eled to the hospital to work with the sterile processing team on the investigation. Maintenance records showed that the preventive maintenance work was current and there were no other reported issues with the sterilizer. The investigation then focused on the cycle records for the DUO cycles, including load records and cycle printouts. The cycle printouts and chemi- cal indicators did not show any evidence of a problem in the failed cycles. It became evident, however, that the positive BIs were always associated with a particular load consisting of two cystoscopes in large trays containing silicone mats and wrapped with heavy duty disposable wrap. The total weight of this load was 14.8 lbs. After considering this information, a decision was made to reduce the load weight by only processing 1 cystoscope at a time. The manufacturer’s maximum load for the DUO cycle was 13.2 lbs. so this change brought the load weight into align- ment with the sterilizer and tray IFU. The silicone mats were also removed, as they were not part of the IFU. No additional BI positives occurred after these changes were implemented. BIs once again demonstrated that they are the best method for detecting prob- lems with the quantity or quality of the sterilant. Hydrogen peroxide is a very unstable and reactive chemical, so it is prone to situations, such as condensation, absorption, or chemical breakdown, that
34 April 2021 • HEALTHCARE PURCHASING NEWS •
hpnonline.com
which was detected by the BIs. It is also worth noting that it is extremely important to read and follow all manufacturers’ IFU associated with VH2
O2
prevent sterilization process failures. Summary
O2
BIs are the only indicators that contain viable microorganisms and directly mea- sure the effectiveness of the sterilization process. They are intended to be used with physical monitors and chemical indicators as part of a comprehensive sterilization quality control testing program. A positive BI is evidence that a sterilization process failure has occurred. These failures should be carefully investigated to determine the root cause and correct the problem. HPN
References:
1. International Organization for Standardization. Sterilization of healthcare products — Vocabulary of terms used in sterilization and related equipment and process standards. ISO 11139:2018. Geneva, Switzerland. ISO, 2018
2. Rutala, WE et al. Guideline for Disinfection and Sterilization in Health Care Facilities, 2008. (Updated May 2019), CDC.
3. International Organization for Standardization. Sterilization of healthcare products — BIs. . ISO 11138 Parts 1-5:2017. Geneva, Switzerland. ISO, 2017
4. ANSI/AAMI ST79, Comprehensive guide to steam sterilization and sterility assurance in healthcare facilities. Association for the Advancement of Medical Instrumentation. 2017.
5. ANSI/AAMI ST58, Chemical sterilization and high-level disinfec- tion in healthcare facilities. Association for the Advancement of Medical Instrumentation. 2013.
3M Health Care sponsored this article. Craig Wallace, president of Wallace Steril- ization Consulting, LLC, has over 26 years of experience in the field of medical device disinfection and sterilization. Craig is the Convenor of the ISO BI Working Group (TC 198, Working Group 4), the ISO committee responsible for
international BI performance standards, as well as a U.S Technical Expert for Chemical Indicators (ISO WG 6) and Moist Heat Ster- ilization (WG 3). He is also the Co-Chair of the United States (AAMI) BI Working Group, and an active member of several other AAMI working groups including chemical indicators, vaporized hydrogen peroxide sterilization, and ethylene oxide sterilization.
can reduce its concentration in the cham- ber - therefore reducing the killing power of the sterilization process. In this case, the oversized load likely absorbed, and possibly condensed, too much hydrogen peroxide during the process. It is also likely that the tray liner mats were absorb- ing hydrogen peroxide. The net result was too little VH2
remaining in the process, sterilization to help
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
