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Low-Temperature Sterilization: Characteristics, Benefits, Monitoring

Low-Temperature Sterilization: Characteristics, Benefits, Monitoring. William A. Rutala, PhD, MPH

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Low-Temperature Sterilization: Characteristics, Benefits, Monitoring

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  1. Low-Temperature Sterilization: Characteristics, Benefits, Monitoring William A. Rutala, PhD, MPH Director, Hospital Epidemiology, Occupational Health and Safety at UNC Health Care System; Professor of Medicine and Director, Statewide Program for Infection Control and Epidemiology at University of North Carolina at Chapel Hill, USA Disclosure-3M

  2. Low-Temperature Sterilization • Provide overview of low-temperature sterilization • Characteristics • Benefits • Monitoring

  3. www.disinfectionandsterilization.org

  4. Disinfection and Sterilization in Healthcare FacilitiesWA Rutala, DJ Weber, and HICPAC, www.cdc.gov • Overview • Last Centers for Disease Control and Prevention guideline in 1985 • 158 pages (>82 pages preamble, 34 pages recommendations, glossary of terms, tables/figures, >1000 references) • Evidence-based guideline • Cleared by HICPAC February 2003; delayed by FDA • Published in November 2008

  5. Disinfection and Sterilization EH Spaulding believed that how an object will be disinfected depended on the object’s intended use. CRITICAL - objects which enter normally sterile tissue or the vascular system or through which blood flows should be sterile. SEMICRITICAL - objects that touch mucous membranes or skin that is not intact require a disinfection process (high-level disinfection [HLD]) that kills all microorganisms but high numbers of bacterial spores. NONCRITICAL -objects that touch only intact skin require low-level disinfection (or non-germicidal detergent).

  6. Efficacy of SterilizationInfluencing Factors Cleaning of the object Organic and inorganic load present Type and level of microbial contamination Concentration of and exposure time to disinfectant/sterilant Nature of the object Temperature and relative humidity

  7. Processing “Critical” Patient Care Objects Classification: Critical objects enter normally sterile tissue or vascular system, or through which blood flows. Object: Sterility. Level germicidal action: Kill all microorganisms, including bacterial spores. Examples: Surgical instruments and devices; cardiac catheters; implants; etc. Method: Steam, gas, hydrogen peroxide gas plasma, vaporized hydrogen peroxide, ozone or chemical sterilization.

  8. Critical Objects • Surgical instruments • Cardiac catheters • Implants

  9. Sterilization The complete elimination or destruction of all forms of microbial life and is accomplished in healthcare facilities by either physical or chemical processes

  10. Sterilization of Patient Equipment • Alternatives to ETO-CFC ETO-CO2, ETO-HCFC, 100% ETO • Newer Low Temperature Sterilization Technology Hydrogen Peroxide Gas Plasma Vaporized hydrogen peroxide Ozone-not commonly used

  11. Cleaning • Mechanical cleaning machines-automated equipment may increase productivity, improve cleaning effectiveness, and decrease worker exposure • Utensil washer-sanitizer • Ultrasonic cleaner • Washer sterilizer • Dishwasher • Washer disinfector • Manual

  12. STERILIZATION Factors affecting the efficacy of sterilization • Bioburden • Cleaning • Pathogen type • Protein and salt • Biofilm accumulation • Lumen length and diameter • Restricted flow

  13. Lumens Sterilized by VariousLow-Temperature Sterilization Methods Challenge: 12/88 100%ETO HCFC-ETO Sterrad 10% Serum, 0.65% Salt (7 organisms, N=63) 44% 39.7% 49.2% 35% No Serum or Salt, (3 organisms, N=27) ND 96.3% 96.3% ND Alfa et al. Infect Cont Hosp Epidemiol 1996;17:92-100. The three organisms included: E. faecalis, M. chelonei, B. subtilis spores. The seven organisms included: E. faecalis, P. aeruginosa, E.coli, M. chelonei, B. subtilis spores, B. stearothermophilus spores, B. circulans spores

  14. Low-Temperature Sterilization Technologies (LTST)Conclusions • All LTST technologies have limitations • LTST (ETO, HP gas plasma) demonstrate a significant number of failures in presence of serum or salt • Salt and serum provide protection for spores and bacteria • Salt and serum combined with a narrow lumen provide extraordinary protection with LTST

  15. IS THERE A STANDARD TO DEFINE WHEN A DEVICE IS CLEAN? • There is currently no standard to define when a device is “clean”, cleanliness controlled by visual • Potential methods: level of detectable bacteria; protein (6µg/cm2); endotoxin; ATP; lipid • This is due in part to the fact that no universally accepted test soils to evaluate cleaning efficiency and no standard procedure for measuring cleaning efficiency • At a minimum, a cleaning process should: reduce the natural bioburden; remove organic/inorganic contaminants; provide devices that when sterilized have a SAL 10-6

  16. Verifying Cleaning Processes • AAMI recommends incorporating test methods that verify the functionality of the automated washer • Washer indicators have been in use in Europe and Canada and some US hospitals • Washer indicators are chemical indicators imprinted with a dried test soil formula and a dye.

  17. Cleaning Indicators for Washers • Monitor the automated washer and instrument cleaning chemistry functionaiity • Indicator includes proteins, lipids, and polysaccharides to mimic common challenging test soils

  18. Low-Temperature Sterilization • Provide overview of low-temperature sterilization • Characteristics • Benefits-sterilize temperature and moisture-sensitive medical and surgical devices in health care • Review advantages/disadvantages of LTS technology • Monitoring

  19. 100% Ethylene Oxide4.8 ft3 chamber

  20. Ethylene Oxide (ETO) • Advantages • Very effective at killing microorganisms • Penetrates medical packaging and many plastics • Compatible with most medical materials • Cycle easy to control and monitor • Disadvantages • Some states (CA, NY, TX) require ETO emission reduction of 90-99.9% (air pollution control device) • CFC (inert gas that eliminates explosion hazard) banned after 1995 • Potential hazard to patients and staff • Lengthy cycle/aeration time

  21. Ethylene Oxide Aeration • The ability to penetrate is an important characteristic of ETO • It is this property that necessitates extended periods of aeration • During aeration, heated air is flushed through chamber to remove ETO residuals from sterilized items • Consult the medical device manufacturer for recommended aeration times • Composition of device • Intended application

  22. Ethylene Oxide Aeration Aeration Time Guidelines* Temperature Aeration Time 50°C 12 hours 60°C 8 hours * Based on polyvinylchloride (PVC) tubing Ref: ANSI/AAMI ST41:2008 Section 8.8.4

  23. OSHA Occupational Exposure Standard for ETOExposure Limits Employer required to monitoremployee exposure WHAT? • Monitor for 8-hour TWA • 15 minute sampling period HOW? • Breathing zone air samples WHO? • Representative employee on each shift for each job classification If ETO exposure  0.5 ppm Action Level, 8-hr TWA-monitoring of those employees can be discontinued 3M™ Ethylene Oxide Monitor 3550

  24. Hydrogen Peroxide Gas Plasma

  25. Hydrogen Peroxide Gas Plasma Sterilization Advantages • Safe for the environment and health care worker; it leaves no toxic residuals • Fast - cycle time is 28-52 min and no aeration necessary • Used for heat and moisture sensitive items since process temperature 50oC • Simple to operate, install, and monitor • Compatible with most medical devices

  26. Hydrogen Peroxide Gas Plasma Sterilization Disadvantages • Cellulose (paper), linens and liquids cannot be processed • Sterilization chamber , about 3.5ft3 to 7.3ft3 • Endoscopes or medical devices restrictions based on lumen internal diameter and length (see manufacturer’s recommendations); expanded claims with NX • Requires synthetic packaging (polypropylene) and special container tray

  27. Advantages Safe for the environment and health care worker; it leaves no toxic residuals Fast - cycle time is 55 min and no aeration necessary Used for heat and moisture sensitive items (metal and nonmetal devices) Disadvantages Sterilization chamber is small, about 4.8ft3 Medical devices restrictions based on lumen internal diameter and length-see manufacturer’s recommendations, e.g., SS lumen 1mm diameter, 125mm length Not used for liquid, linens, powders, or any cellulose materials Requires synthetic packaging (polypropylene) Limited use and limited comparative microbicidal efficacy data V-PRO™1, Vaporized Hydrogen Peroxide

  28. Ozone • Advantages • Used for moisture and heat-sensitive items • Ozone generated from oxygen and water (oxidizing) • No aeration because no toxic by-products • FDA cleared for metal and plastic surgical instruments, including some instruments with lumens • Disadvantages • Sterilization chamber small, 4ft3 • Limited use (material compatibility/penetrability/organic material resistance?) and limited microbicidal efficacy data

  29. ConclusionsSterilization • All sterilization processes effective in killing spores • Cleaning removes salts and proteins and must precede sterilization • Failure to clean or ensure exposure of microorganisms to sterilant (e.g. connectors) could affect effectiveness of sterilization process

  30. RecommendationsMethods of Sterilization • Steam is preferred for critical items not damaged by heat • Follow the operating parameters recommended by the manufacturer (times, temperatures, gas conc) • Use low temperature sterilization technologies for reprocessing critical items damaged by heat • Aerate surgical and medical items that have been sterilized in the ETO sterilizer

  31. Alternatives to ETO-CFC ETO-CO2, ETO-HCFC, 100% ETO New Low Temperature Sterilization Technology Hydrogen peroxide gas plasma-most common Vaporized hydrogen peroxide-limited clinical useOzone and hydrogen peroxide-not FDA cleared Nitrogen dioxide-not FDA cleared Newer Trends in Sterilization of Patient Equipment

  32. Low-Temperature Sterilization • Provide overview of low-temperature sterilization • Characteristics • Benefits-sterilize temperature and moisture-sensitive medical and surgical devices in health care • Monitoring

  33. Monitoring of Sterilizers • Use physical, chemical and biological monitors to ensure the effectiveness of the sterilization process • Each load should be monitored with physical and chemical indicators • If the physical, chemical or biological indicators suggest inadequate processing, the items should not be used • Biological indicators should be used at least weekly (commonly daily or each load) with spores intended specifically for the type of sterilizer

  34. Objectives of Monitoring the Sterilization Process • Assures probability of absence of all living organisms on medical devices being processed • Detect failures as soon as possible • Removes medical device involved in failures before patient use

  35. Sterilization Monitoring Sterilization monitored routinely by combination of physical, chemical, and biological parameters • Physical - cycle time, temperature, pressure • Chemical - heat or chemical sensitive inks that change color when germicidal-related parameters present (Class 1-6) • Biological - Bacillus spores that directly measure sterilization

  36. Biological Indicators • Select BIs that contain spores of Bacillus atrophaeus • Rationale: BIs are the onlysterilization process monitoringdevice that provide a direct measure of the lethality of the process

  37. Biological Monitors • ETO - B. atrophaeus • New low temperature sterilization technologies HP gas plasma (Sterrad) and HP vapor (V-Pro)- G. stearothermophilus Ozone-G. stearothermophilus

  38. Process Challenge Device (PCD) “A PCD is a device used to assess the effective performance of a sterilization process by providing a challenge to the process that is equal or greater than the challenge posed by the most difficult item routinely processed.” • PCD may be: • User-assembled test pack • Commercially available, FDA cleared preassembled test pack • ST41 describes two types of PCDs • Routine BI test pack • Challenge BI test pack

  39. Ethylene Oxide Sterilization Recommended Monitoring Practices • Routine Load Release/Sterilizer Efficacy Monitoring • Physical monitoring of cycle • External and internal monitoring of packages • Monitoring of every load with a PCD (routine test pack) containing a BI and a CI or equivalent, commercially available BI PCD • Ideally, quarantine implants until BI results are known ANSI/AAMI ST41:2008, Section 10

  40. Ethylene Oxide • BI placed in full load in center • Frequency, in each load • Visual, color 48 hour readout • Rapid readout BI for ETO provides 4hr (not shown)

  41. Hydrogen Peroxide Gas Plasma • Provides evidence that proper sterilization conditions were achieved in 24 hours • Built-in chemical indicator confirms it has been exposed to HP if color changed from red to yellow • Placed in peel pack on bottom rack with tyvek side up 1x per day • CI placed in every load

  42. Monitoring of Sterilizers • Internal Chemical Indicator • Validates the sterilant penetrated the pack or tray • Advantage of the pack control monitor is that it is inside each pack in multiple locations • Detect local problem

  43. RecommendationsMonitoring of Sterilizers • Following a single positive biological indicator used with a method other than steam, treat as non-sterile all items that have been processed in that sterilizer, dating back to last negative biological indicator. These non-sterile items should be retrieved, if possible, and reprocessed.

  44. Routine Load Release/Routine Sterilizer Efficacy Monitoring Acceptance criteria • Appropriate readings from physical monitors • Appropriate readings from CIs • Negative result from BI in PCD • Positive BI control result • Run a control BI, with matching lot #, each day • Document all results in sterilization cycle record ANSI/AAMI ST41:2008, Section 10

  45. RecommendationsStorage of Sterile Items • Sterile storage area should be well-ventilated area that provides protection against dust, moisture, and temperature and humidity extremes. • Sterile items should be stored so that packaging is not compromised • Sterilized items should be labeled with a load number that indicates the sterilizer used, the cycle or load number, the date of sterilization, and the expiration date (if applicable)

  46. Conclusions • All sterilization processes effective in killing spores • Cleaning removes salts and proteins and must precede sterilization • Delivery of sterile products for use in patient care depends not only on the effectiveness of the sterilization process but also on cleaning, disassembling and packaging of the device, loading the sterilizer, and monitoring

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