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Sterilization & Disinfection
- 1. Sterilization & Disinfection 1 By: Dr Rohan Bhoil
- 2. Outline ⢠Overview of disinfection and sterilization. ⢠Various methods. ⢠Important perspectives.
- 3. Definitions 3 Sterilization: complete killing of all forms of microorganisms, including bacterial spores. Disinfection: killing or removing of harmful vegetative microorganisms. Antiseptic: disinfectant that can be safely used on living tissues.
- 4. Definitions 4 Bacteriocide kill microbes also germicide, fungicide, virucide Bacteriostatic Prevents or stops microbial growth also fungistatic, virustatic Aseptic(Asepsis) Prevent contamination of person or object by microbes
- 5. Definitions ⢠Sanitize âRemoval of pathogens from inanimate objects âMechanical or chemical cleaning âneed not sterilize of disinfect ⢠Contamination âPresence of living microbes on object
- 6. History ⢠In 1862, Louis Pasteur developed pasteurization process. ⢠Joseph Lister, in 1867, used a carbolic solution spray on the wounds of his patients. ⢠Charles Chamberland, developed the first pressure steam sterilizer, or autoclave in 1876.
- 9. Survival of Pathogens on Surfaces Pathogen Survival MRSA 7 days â 7 months VRE 5 days â 4 months Acinetobacter 3 days -5 months C. difficile (spores) 5 months Norovirus 12 â 28 days HIV Minutes to hours HBV 7 days HCV 16 hours â 4 days
- 10. Order of resistance 10 Hardest to Kill â˘Prions â˘Spores â˘Mycobacteria â˘Non-enveloped viruses â˘Fungi â˘Vegetative bacteria â˘Enveloped virusesEasiest to Kill
- 11. Methods of sterilization and disinfection PHYSICAL METHODS CHEMICAL METHODS â˘SUNLIGHT ⢠DRYING ⢠DRY HEAT ⢠MOIST HEAT ⢠FILTRATION ⢠RADIATION ⢠ULTRASONIC AND SONIC VIBRATIONS â˘ALCOHOLS ⢠ALDEHYDES ⢠DYES ⢠HALOGENS ⢠PHENOLS ⢠SURFACE-ACTIVE AGENTS ⢠METALLIC SALTS ⢠GASES
- 12. Choice of Method ⢠Method to be used will depend on: âDeviceâs intended use âRisk of infection âDegree of soilage ⢠Process must not damage the device
- 14. Management of contaminated items 14 Contaminated reusable items should be: â˘Handled as little as possible â˘Staff should wear appropriate PPE â˘Gross debris removed at point of use â˘Soiled items removed immediately after use
- 15. It all starts with cleaning 15 Items canât be disinfected or sterilized unless they are properly cleaned.
- 16. Cleaning instruments 16 â˘Soak in enzymatic or non- enzymatic detergent â˘Wear the appropriate PPE â˘Keep instruments submerged in solution and scrub with brush â˘Thoroughly rinse the instrument â˘Allow instrument to dry
- 17. Automated cleaning 17 Types: ⢠Ultrasonic cleaner ⢠Instrument washer Benefits: ⢠Improved efficacy ⢠Reduced employee exposure to splash and sharps
- 18. Disinfectants
- 19. Activity of disinfectants 19 â˘Contamination â˘Concentration â˘Temperature â˘Time â˘Range of action
- 20. High-Level Disinfectants Germicide Concentration Glutaraldhyde (Cidex) ⼠2.0% Ortho-phthaladehyde (Cidex OPA) 0.55% Hydrogen Peroxide* (Sporox) 7.5% Hydrogen Peroxide and peracetic acid* (Peract) 1.0% / 0.08% Hydrogen Peroxide and peracetic acid* (Endospore +) 7.5% / 0.23% Hypochlorite (free chlorine)* (Sterilox Š) 650-675 ppm Accelerated hydrogen peroxide (Resert XL) 2.0% Peracetic Acid (Steris 20) 0.2% Glutaraldehyde and Isopropanol (Aldahol III) 3.4% / 26% Glutaraldehyde and phenol/phenate (Sporicidin) 1.21% / 1.93%
- 21. Liquid Disinfectants Disinfectant Agent Use Concentration Ethyl or isopropyl alcohol 70% - 90% Chlorine (bleach) 100 ppm Phenolic UD Iodophor UD Quaternary ammonium compound (QUAT) UD Improved/Accelerated hydrogen peroxide 0.5%, 1.4%
- 22. Sterilization
- 23. Dry Heat Sterilisation ⢠Require hot-air ovens ⢠For glassware, metallic items, powders and oil/grease ⢠Time two hours at 160°C and one hour at 180°C ⢠Plastics, rubber, paper and cloth cannot be placed in them due to fire risk
- 24. Dry Heat Sterilisation Advantages ⢠Can be used for powders, anhydrous oils ⢠Inexpensive ⢠No corrosive effect on instruments Disadvantages ⢠High temperature damages some items ⢠Penetration of heat slow, uneven
- 25. Autoclave Pressure (psi) Temperature (°C) Time (mins) 15 121 15 20 126 10 20 134 3
- 26. Types of autoclave ⢠Downward displacement ⢠Positive pressure displacement ⢠Negative pressure displacement ⢠Triple vacuum autoclave
- 27. Gravity Displacement Autoclaves ⢠Steam introduced to purge out air and build pressure ⢠Raise temperature normally to 121°C at 15 pounds/square inch and maintain it for 15-45 minutes ⢠For sterilising liquids and items in wraps that steam can penetrate
- 28. High-Vacuum Autoclaves ⢠Air is first vacuumed out and then steam introduced ⢠Faster and better penetration throughout the load ⢠Pressure and temperature higher; 134°C at about at 30 pounds/inch2 ⢠Processing time about three minutes ⢠Not suited for liquids due to need for vacuum
- 29. Low-Temperature Sterilization ⢠Mixture of steam (50-80°C) and formaldehyde vapour ⢠To process heat-resistant or heat- sensitive medical devices in specialised equipment ⢠Devices pre-cleaned and wrapped in standard material and processed in a three-hour cycle ⢠Cannot be used for liquids ⢠Formaldehyde must be purged/ neutralised well
- 30. Flash Sterilisation Only to process a critical surgical item: in an emergency when accidentally contaminated, or when other means of sterilisation unavailable Never to be used for implantable items or to compensate for shortage of key instruments
- 31. Ethylene Oxide Gas Sterilisation ⢠Used for heat or moisture sensitive items ⢠Prevents normal cellular metabolism and replication
- 32. Hydrogen Peroxide Gas Plasma ⢠Highly reactive/charged particles from hydrogen peroxide generated under vacuum ⢠Can be used to sterilise heat- and moisture-sensitive items â Some plastics, electrical/electronic devices, and corrosion-susceptible metal alloys ⢠Special wrapping required
- 33. Fumigation ⢠For rooms contaminated with some pathogens â Such as MRSA and Clostridium difficile ⢠Release of hydrogen peroxide, chlorine dioxide gas or possibly ozone in sealed rooms ⢠Spore strips (biological indicators) placed strategically to monitor process ⢠Special equipment required ⢠Risk of damage to sensitive items
- 34. Pasteurisation and Boiling ⢠Semi-critical items can be pasteurised â 65-77°C, 30 min â Example: respiratory therapy equipment ⢠Must be retrieved carefully for safe transport and storage
- 35. Filtration ⢠Removal of microbes from air or heat-sensitive liquids ⢠Disinfectant-impregnated filters may inactivate trapped microorganisms ⢠Example: High-efficiency particulate air (HEPA) filters ⢠All filters must be checked for integrity and replaced as necessary
- 36. Ultraviolet (UV) Light ⢠UV lamps useful for chemical-free disinfection of air and water and also possibly for decontamination of environmental surfaces ⢠Broad-spectrum microbicidal action ⢠Require regular cleaning and periodic replacement
- 37. Microwaves ⢠Heating from rapid rotation of water molecules ⢠Limited use except for disinfecting soft contact lenses and urinary catheters for intermittent self- catheterisation ⢠May be used in emergencies to treat water for drinking or to âdisinfectâ small water-immersible plastic or glass items
- 38. Wrapped or Packaged Instrument Sets in Autoclave 39 Item Time Temperature Pressure Notes Small wrapped or packaged loads 15 minutes Add 5 min to allow for reaching parameters 270° F (132°C) 30 psi Drying time 15-30 min No drying time â packs must be handled with sterile gloves *Not recommended without use of minimum drying times
- 39. Instrument wrap 40 ⢠Should be square wrap with a 6 inch border around each side of the pan. ⢠Alternative wrap: 140- thread count, 100% cotton muslin.
- 40. Wet packs? 41 Cause Solution Over packed autoclave Run smaller loads Dehydrated wrap Launder wrap after each use Short drying time Extend drying times Stored on solid cool surface Store on wire mesh shelving
- 41. Storage of Sterile Items 42 â˘A well-ventilated area that provides protection against dust, moisture, and temperature and humidity extremes. â˘Sterile items should be stored so that packaging is not compromised. â˘Label sterilized items with a load number that indicates the sterilizer used, the cycle or load number, the date of sterilization, and if applicable the expiration date.
- 42. Monitoring 43 Autoclave tape â external indicator Chemical indicator â internal indicator Indicators should be checked prior to using any item. No color change â do not use and return for proper sterilization.
- 43. Biological monitors METHOD OF STERILIZATION BIOLOGICAL CONTROL â˘Hot Air Oven ⢠Autoclave â˘Filtration ⢠Ionizing Radiation Bacillus subtilis subsp. Niger Clostridium tetani Bacillus stearothermophilus Serratia marcescens, Pseudomonas diminuta Bacillus pumilis
- 44. Dental Surgery Perspective 45 Gigasept which contains succindialdehyde and dimethoxytetrahydrofuran are used for disinfection of plastic and rubber materials eg: dental chair
- 45. Asepsis of surgical theaters Fumigation is done by two methods: ⢠Electric boiler method ⢠Potassium permanganate
- 46. BIOPSY SPECIMEN Biopsy collection & transportation can also be a source of infection. ⢠It should be kept in sturdy containers with secure lid. ⢠Avoid contaminating the external surface of the container. ⢠Swab used for collecting micro- organisms should be transferred slowly and carefully to the swab container
- 47. Impression Trays Impression trays are sterilized as follows ⢠metallic - autoclave ⢠plastic â ethylene oxide Disinfection of alginate impressions â Methods ⢠- Spraying ⢠- Immersion ⢠Iodophors, sodium hypochlorite (1:10 concentration ) , ⢠phenols, formaldehyde, glutaraldehyde.
- 48. DENTAL CASTS Spraying until wet or Immersing in a 1:10 dilution of sodium hypochlorite or an iodophor then rinse Casts to be disinfected should be fully set (i.e. stored for at least 24 hours
- 49. ROTARY INSTRUMENTS - BURS Diamond and carbide burs: After use they are placed in 0.2% gluteraldehyde and sodium phenate (Eg. Sporicidin) for at least 10 minutes, cleaned with a bur brush or in an ultrasonic bath. Sterilize in an autoclave or dry heat Steel burs: May get damaged by autoclaving. Can be sterilized by using a chemical vapor sterilizer or glass bead sterilizer at 2300C for 20-30 seconds.
- 50. INSTRUMENTS Sharp instruments are ideally sterilized by : conventional hot air oven BUT NOT BY: Boiling Autoclave 2% glutaraldehyde Blunt instruments are sterilized by Autoclave
- 51. Sutures Sutures are pre sterilized by gamma radiation Sutures are re- sterilized by two recommended methods 1. Soak for a full 10 minutes completely immersed in povidone iodine 10% solution, then rinse in sterile saline/water. 2. Ethylene Oxide â gas sterilisation.
- 52. ENDODONTIC INSTRUMENTS ⢠Glass Bead or salt sterilizer ⢠Gutta percha points are pre- sterilized. ⢠Contaminated points are sterilized by 5.25% sodium hypochlorite(1 min immersion). Then rinse with hydrogen peroxide & dry it.
- 53. IMPLANTS Pre sterilized with Gamma radiation In case the implants needs to be re-sterilized conventional sterilization techniques are not satisfactory Steam / Dry heat sterilization should not be used Radio frequency glow discharge technique (RFGDT) or Plasma cleaning is used.
- 54. Take home points 55 Cleaning, disinfection, and sterilisation are the backbone of infection prevention and control Proper cleaning is essential before any disinfection or sterilisation process
- 55. Take home points 56 Steam sterilisation is effective only when preceded by Thorough pre-cleaning, proper packaging/loading, and careful monitoring of autoclaves. Chemical disinfectants must be selected, used, and discarded to minimise harm.
- 56. References ⢠Yoo JH. Principle and perspective of healthcare-associated infection control. J Korean Med Assoc. 2018;61:5â12. ⢠Stokes HW, Gillings MR. Gene flow, mobile genetic elements and the recruitment of antibiotic resistance genes into Gram-negative pathogens. FEMS Microbiol Rev. 2011;35:790â819. ⢠Rutala WA, Weber DJ. Disinfection, sterilization, and antisepsis: An overview. Am J Infect Control. 2016;44(Suppl):e1âe6. ⢠McDonnell G, Russell AD. Antiseptics and disinfectants: activity, action, and resistance. Clin Microbiol Rev. 1999;12:147â179. ⢠Rutala WA, Weber DJ. Disinfection and sterilization in health care facilities: what clinicians need to know. Clin Infect Dis. 2004;39:702â709. ⢠Rutala WA, Weber DJ. Disinfection and sterilization in health care facilities: an overview and current issues. Infect Dis Clin North Am. 2016;30:609â637. ⢠Cadenas E. Biochemistry of oxygen toxicity. Annu Rev Biochem. 1989;58:79â110. ⢠Hayyan M, Hashim MA, AlNashef IM. Superoxide ion: generation and chemical implications. Chem Rev. 2016;116:3029â3085. ⢠Russell AD. Bacterial spores and chemical sporicidal agents. Clin Microbiol Rev. 1990;3:99â119. ⢠Alexanderâs Care of the Patient in Surgery, Jane C. Rothrock, 15th edition, Mosby Elsevier, 2015. ⢠Berry & Kohnâs Operating Room Technique, Nancymarie Phillips, 12th edition, Mosby Elsevier, 2012. ⢠Essentials of Perioperative Nursing, Goodman and Spry, 5th edition, Jones and Bartlett Learning, 2014. ⢠Perioperative Standards and Recommended Practice, Association of Perioperative Registered Nurses (AORN), 2014 edition. ⢠Surgical Technology for the Surgical Technologist: A Positive Care Approach, American Association of Surgical Technologist (AST), 4th edition, Delmar, 2012.
- 57. Questions ?
Editor's Notes
- In-depth knowledge of disinfection and sterilization is a key component of infection control.
- Disinfection and sterilization are essential for ensuring that medical and surgical instruments do not transmit infectious pathogens to patients. AS sterilization of all patient-care items is not necessary, health-care policies must identify, primarily on the basis of the itemsâ intended use, whether cleaning, disinfection, or sterilization is indicated.
- Once epidemiologically important pathogens are on surfaces, many can live for quite some time. According to numerous studies published in the literature, many of these pathogens can live from days to several months on dry surfaces. The human immunodeficiency virus (HIV) does not survive well outside of the host, while hepatitis C virus can survive for up to 4 days and hepatitis B virus can survive up to a week on a surface
- Prions (Creutzfeldt-Jakob Disease (CJD), mad cow disease) Spores (C. difficile) Mycobacteria (Tb) Non-enveloped viruses Fungi (Candida) Vegetative bacteria (MRSA) Enveloped viruses (HIV, HBV)
- Heat :- most reliable and commonly applied way of sterilization - most common forms are Dry heat and moist heat DRY HEAT Principle- - Protein denaturation. - Oxidative damage.
- Practical tips for using water for cleaning, disinfection and sterilisation Use clean water (preferably filtered or boiled) for cleaning, disinfecting and sterilising. In areas where tap water and surface water have a high mineral or salts content use clean (filtered or boiled) rainwater for cleaning, preparing disinfection solutions and sterilising. Water with a high mineral or salts content can damage equipment and instruments causing scaling, furring and corrosion of boilers and sterilisers. Boiling or filtering does not reduce the mineral or salts content of water but will ensure that the water is clean. Use cool or warm water for cleaning not hot water. Hot water causes protein substances (such as organic matter) to stick to instruments and equipment.
- Dr. Earle Spaulding devised a rational approach to disinfection and sterilization of patient care items based on the itemâs intended use. He categorized every patient care item into one of three categories based on risk: critical, semi-critical, and non-critical. The level of disinfection or sterilization depends on the categorical classification of the item. We are going to start with critical items. These items contact sterile tissue, for example sterile instruments and must be sterilized ; semi-critical items that contact mucous membranes, like endoscopes, or non-intact skin, like wound therapy equipment, require high-level disinfection; and non-critical items that have contact only with intact skin, like stethoscopes, require low-level disinfection. basically The selection of a disinfection or sterilization method depends on the intended use of the item. Non-critical requires low level disinfection Semi-critical requires high level disinfection Critical requires sterilization
- Contaminated reusable items should be handled as little as possible When handling contaminated items appropriate PPE should be used Gross soil or debris should be removed at the point of use (gauze sponge moistened with water/disinfectant wipe for example) Soiled items should be immediately contained and transported to the decontamination area or soiled utility room where cleaning procedures can be accomplished away from patient care
- The first step is to remove all visible and invisible soils Must be done according to manufacturerâs guidelines Neutral PH enzymatic detergent, mechanical friction Next step is generally the mechanical washer
- One of the most important factors is pre-cleaning of the medical device or equipment. When blood or other body fluids is present it can act as a barrier and make it more difficult to disinfect or sterilize the item. Cleaning and decontamination should be done as soon as possible after the items have been used to avoid material drying on the device Medical devices may be pre-cleaned either manually or by an automated process, (use of an instrument washer designed specifically for medical devices). In the outpatient setting manual cleaning is the most common. Steps for manual cleaning include: Soaking the item in an enzymatic or non-enzymatic detergent solution per the manufacturer instructions Scrub with a brush if necessary to remove all of the material Thoroughly rinsing of the equipment and Allow instrument to dry ALWAYS REMEMBER Do not use high-level disinfection and sterilization solutions for holding instruments To avoid injury from sharp instruments, the provider should wear puncture-resistant, heavy-duty utility gloves (not patient care gloves), and proceed with care when handling or manually cleaning contaminated instruments and devices to avoid a percutaneous injury. To protect against splashes, a facemask, eye protection or face shield, and a fluid resistant gown should be worn.
- The other and most efficient method of cleaning is using automated or mechanical cleaning equipment, such as ultrasonic cleaners, instrument washers, and washer-disinfectors. Automated cleaners: Improve the efficacy of the cleaning process Reduce the handling of sharp instruments. Reduce the risk of employee exposure The manufacturerâs recommendations for dilution, temperature, water hardness, and use (designed for use in washer-disinfectors) should be followed. After cleaning, instruments should be rinsed with water to remove chemical or detergent residue.
- Activity directly proportional to temperature. 2. Directly proportional to concentration up to a point â optimum concentration. After this level no advantage in further increases in concentration. Disinfectants may be inactivated by : Dirt Organic matter : Proteins, Pus, Blood, Mucus and Feces. Non organic: Cork, Hard water and Some plastics. 4. Time : Disinfectants need time to work. 5. Range of Action : Disinfectants not equally effective against the whole spectrum of microbes. e.g. Chlorhexidine less active against Gram negative bacteria than Gram positive cocci. Hypochlorites and Gluteraldehyde are more active against hepatitis viruses than most other disinfectants.
- There are many products on the market that can be used for high-level disinfection of semi-critical items. It is important that you use a product that has been cleared by the FDA as a sterilant and high-level disinfectant. You should follow the manufacturerâs instructions for use to achieve high-level disinfection, specifically in regards to concentration, exposure time and in-use temperatures. Material compatibility is also a factor, so it is important to choose the disinfectant that will not damage the item undergoing high-level disinfection.
- These are examples of commonly used disinfectants in healthcare. A quaternary ammonium compound is a commonly used product, but there are new products on the market including an improved or accelerated hydrogen peroxide. Most of these preparations come in ready to use forms that do not require any additional mixing of dilution
- Hot-air ovens are used for dry-heat sterilisation. They can reach high temperatures and should be equipped with a fan for even distribution of heat. Preheating is essential before starting the sterilisation cycle. Hot-air ovens are simpler in design and safer for use than autoclaves and are suitable for sterilisation of glassware, metallic items, powders, and anhydrous materials (oil and grease). Sterilisation takes two hours at 160°C, or one hour at 180°C. Plastics, rubber, paper, and cloth must not be placed in them to avoid the risk of fires. Dry heat in an oven kills by oxidation, which is a much slower process. Dry heat is used to sterilise moisture-sensitive materials (powders) or items which steam cannot penetrate (oils and waxes).
- Advantages of dry heat sterilisation include: ⢠the ability to sterilise goods in sealed or non-porous containers ⢠the ability to sterilise complex goods while assembled ⢠the ability to sterilise goods which are impossible to dry in a steam steriliser or which may be damaged/corroded by the moisture of steam sterilisation ⢠the relative mechanical simplicity of a dry heat steriliser Disadvantages of dry heat sterilisation are: ⢠long times involved in heating, sterilising and cooling goods being sterilised ⢠possible damage to packaging materials or to some of the items themselves arising from the high temperatures used ⢠close monitoring and control of sterilisation conditions within packs being sterilised can be very time consuming ⢠due to the high temperature, dry heat sterilisers provide the greatest potential for injury to personnel following contact with parts of the steriliser or the goods being processed (while they are hot), compared to the other in-facility sterilisation processes ⢠equipment at the âlow costâ end of the market does not adequately maintain constant temperature conditions within the steriliser. Purchasers may not be adequately aware.
- When steam comes in contact with a cooler surface it condenses to water and gives up latent heat to that surface. The large reduction in volume of steam sucks in more steam to the site and the process continues till the temperature of article is raised to that of steam Requires direct contact of an item with steam at a required temperature and pressure for a specified time Most reliable Non-toxic Has broad-spectrum microbiocidal activity Good penetrating ability Cheap and easy to monitor for efficacy
- Autoclaves function primarily through either gravity or vacuum-induced or pre-vacuum (prevac) sterilization methods, though some types of autoclaves combine both methods to sterilize. Though both types of autoclaves sterilize through high temperature steam and use pressure as a means to allow steam to displace ambient air in the chamber to penetrate sterilization media, the means by which these mechanisms occur differ and thus, are more conducive to certain types of media over others. This article will outline the basic function of these autoclaves and list the types of sterilization media most associated with each type of autoclave. gravity autoclaves are the most common types of autoclaves in the market and are usually the recommended type of autoclave for most uses.
- In gravity (downward) displacement autoclaves, steam is introduced at the top of the chamber to purge out the cooler and denser air-steam mixture from the bottom of the chamber. The exhaust valve closes when all the air has been removed, thus allowing the pressure to build and temperature to rise. Such autoclaves are used for sterilising liquids and items in wraps that steam can penetrate. The sterilisation step itself normally lasts about 15 minutes at 121°C at 103.4 kilopascal (15 pounds/square inch).
- In high-vacuum autoclaves, the air from the steriliser chamber is first vacuumed out and then steam is introduced allowing faster and better penetration throughout the entire load. The pressure and temperature rise quickly allowing process times of three minutes at 134°C at about 206.8 kilopascal (30 pounds/square inch).
- In the low-temperature steam-formaldehyde (LTSF) process, steam (50-80°C) is used with vapourised formaldehyde to sterilise heat-sensitive medical devices (even those with narrow lumens). As usual, devices are cleaned and then processed. First, a vacuum is created; steam is introduced in several pulses followed by vapourisation of formaldehyde. At the end of the cycle, the formaldehyde is evacuated and completely purged out with several pulses of steam and high vacuum. Chemical and biological indicators are used to monitor the steriliser performance. It cannot be used with liquids and the potential toxicity of formaldehyde remains a concern.
- In a Flash steriliser, steam is used to process surgical items for use when a critical item has become accidentally contaminated during an operation or when no other means of sterilisation are available. It should never be used for implantable items or to compensate for a shortage of essential instruments. Either a gravity-displacement or pre-vacuum autoclave can be used for flash sterilisation of porous or non-porous items without wrapping or with a single wrap. Waiting to read any included BIs is not possible due to the rapid turn-around needed for flash-sterilised items. Unless suitable containers are used, there is a high risk of recontamination of the processed items and also thermal injury to personnel during transportation to the point-of-use. Flash Sterilisation is not accepted in all regions. âFlashâ sterilisation recommendations restrict use to emergencies, such as unexpected surgery, or dropped instruments. âIn most emergency situations, the risk/benefit ratio is low enough that the use of flash sterilized objects is justifiable. In non-emergency situations, however, the risk/benefit ratio is higher, particularly when implantable devices are involvedâ âflashâ sterilizers must never be used for implantables, suction tubing or cannulars or any other product not specifically validated for the âflashâ process
- Ethylene oxide (EO) is used to sterilise items that are sensitive to heat, pressure, or moisture. EO is a colourless gas that is flammable, explosive, and toxic to humans. Two EO gas mixtures are available, one with hydrochlorofluorocarbons (HCFC) the other a mixture of 8.5% EO and 91.5% carbon dioxide; the latter mixture is less expensive. EO concentration, temperature, relative humidity (RH), and exposure time must all be maintained at the right levels during the process to ensure sterilisation. Gas concentration should be 450 to 1200 mg/l, temperature ranges from 37 to 63oC, RH from 40% to 80%, and exposure times from one to six hours. Parametric release is not possible since gas concentrations and RH cannot readily be measured; a BI should be included with each load. The recommended BI is Bacillus atrophaeus; loads should be quarantined until the incubation time of the BI is complete.
- The main disadvantages of EO sterilisation are the long cycle times and high cost. Sterilised items must be aerated well after processing to remove all residues of EO. Risk of personnel exposure to ethylene oxide demands environmental control equipment be in place.
- Gas plasmas are generated in an enclosed chamber under deep vacuum using radio frequency or microwave energy to excite hydrogen peroxide gas molecules and produce charged particles, many of which are highly reactive free radicals. Gas-plasma can be used to sterilise heat- and moisture-sensitive items, such as some plastics, electrical/electronic devices, and corrosion-susceptible metal alloys. The spores of G. stearothermophilus are used as BIs. This is a safe process, and, as no aeration is needed, sterilised items are available for immediate use or storage. However, It is not suitable for devices with dead-end lumens, powders, or liquids. Other disadvantages include the high cost and need for special packaging material since paper or linen cannot be used. In addition, any liquid or organic residues present interfere with the process.
- Recently, there has been much interest in using fumigants to deal with healthcare-associated pathogens such as methicillin-resistant S. aureus and C. difficile in the environment. Several devices are available which vary in cost, the process used, and the degree of field testing they have undergone. A common process is to vaporise a solution of hydrogen peroxide into a sealed room, such as a patient room, for surface decontamination. No post-treatment aeration is necessary because hydrogen peroxide readily breaks down into oxygen and water. Spore strips are strategically placed throughout the room and retrieved later to monitor the effectiveness of the process. Disadvantages include incompatibility with cellulosic materials and potential corrosion of electronic devices. Chlorine dioxide generated on-site may be released as a gas for room decontamination. The rooms must not only be sealed but also darkened to prevent daylight accelerating the breakdown of the gas. Like hydrogen peroxide, chlorine dioxide naturally breaks down into innocuous by-products. Ozone can decontaminate surfaces in enclosed spaces, however it is highly unstable and potentially damaging to a variety of the materials common in health care facilities. However, an ozone-based medical device steriliser is available. It generates the gas from oxygen and at the end of the cycle converts it to oxygen and water by catalysis. The machine claims wide materials compatibility and the ability to handle narrow-lumened devices.
- Semi-critical items, such as respiratory therapy and anaesthesia equipment, can be pasteurised by heating in water. All their parts must remain well-immersed throughout; holding the heat at about 65-77°C for 30 minutes is sufficient. Locations at higher elevations require a longer time because the boiling point of water gets lower the higher one gets from sea-level. Immersion of heat-resistant items in boiling water for about 10 minutes can substantially reduce the pathogen load, but must never be regarded as âsterilisationâ. Pasteurisation and boiling are thus low-tech and chemical-free methods (as long as the water is pure); treated items must be retrieved carefully for safe transport and storage.
- A simple means of removing microbes from air or heat-sensitive liquids is by passage through membrane or cartridge filters. This process retains physical microorganisms based on their size, without killing them unless the filter matrix is impregnated with or exposed to a microbicidal agent. High efficiency particulate air (HEPA) filters are frequently used to remove microbial contamination from air in surgical theatres, microbiology laboratories, and for sterile manufacturing of pharmaceuticals. Their use in hospital wards and waiting rooms is also increasing to reduce the risk of spread of airborne pathogens. HEPA filters must be checked for integrity after installation and have a scheduled maintenance programme. Cartridge filters may be used on air-supply lines to remove microbial contamination. Membrane and cartridge filters with a nominal pore diameter of 0.2 Âľm are quite commonly used in the manufacture of a variety of heat-sensitive biologicals and injectables. Such filters cannot remove viruses due to their much smaller size. Cartridge filters are also common on taps for potable water and inside automatic endoscope reprocessors to protect processed devices from recontamination with bacteria in rinse water. Liquids passed through such filters are often referred to as âsterileâ, although this is not strictly true.
- Recent advances in ultraviolet (UV) lamp technology make the microbicidal potential of short-wave UV radiation viable for a variety of uses. UV lamps are increasingly popular for disinfection of water and wastewater in some regions. UV-based devices are being marketed for the disinfection of air in hospitals and clinics to reduce the spread of airborne pathogens. Devices are being marketed for the disinfection of environmental surfaces in hospitals as well in some regions. UV radiation does not add any chemicals to the water and air being treated, except for the generation of low levels of ozone. However, it cannot penetrate through dirt, and items require direct exposure to the radiation. Such lamps require regular cleaning and periodic replacement; they can still emit visible light even after the UV radiation has diminished.
- Exposure of water-containing items to microwaves generates heat due to friction from rapid rotation of water molecules. Thus far this process has only been used for disinfecting soft contact lenses and urinary catheters for intermittent self-catheterisation. However, small volumes of water could possibly be made safe for drinking by microwaving in a glass or plastic container. Similarly, small glass or plastic objects could be immersed in water and âdisinfectedâ in a microwave oven.
- Wrapped sets require drying time. Drying time requires 15-60 minutes inside autoclave. Packs that are not allowed to dry inside the autoclave are considered unsterile. If hospital requires sets to be wrapped or packaged between cases they must be removed from the autoclave and opened with sterile gloves.
- Wrap must be laundered between uses Disposable wrap must be specific for instrument wrap. It allows for steam penetration and faster drying time.
- If the exterior wrap is damp or wet or if condensate/water droplets are found inside of the pack it must be considered unsterile.
- CDC recommendations for storage of sterile items. The sterile storage area should be a well-ventilated area that provides protection against dust, moisture, and temperature and humidity extremes. Sterile supplies should be stored far enough from the floor (8 to 10 inches), the ceiling (5 inches unless near a sprinkler head or 18 inches from the sprinkler head), and outside walls (2 inches) to allow for adequate circulation, ease of cleaning, and compliance with fire codes. Store sterile items so the packaging is not compromised (e.g., punctured, bent). 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). Closed or covered cabinets are ideal but open shelving may be used for storage. Any package that has fallen on the floor must be inspected for damage to the packaging and contents. If the package is heat-sealed in impervious plastic and the seal is still intact, the package should be considered not contaminated. If undamaged, items in packaged plastic need not be reprocessed. If damaged, reprocess.
- Autoclave tape â external indicator indicates that set has been exposed to process parameters. Chemical indicator â internal indicator indicates that process parameters have been met in the interior of the wrapped or packaged set Chemical indicators (CI) are used to assess if the required time and temperature were attained during the sterilisation process. One type of CI is an autoclave tape that can be affixed to the outside of a package; it shows a colour change if the package was exposed to heat. Though CIs are not meant to indicate that a product has been sterilised, they can help to detect equipment malfunctions and identify procedural errors. Indicator strips, such as TST (TimeSteamTemperature), should be used â ideally during every sterilisation cycle or at least once a week â to make sure sterilisation has been satisfactorily carried out. Class 5 chemical indicator: Is an integrating indicator. This chemical indicator reacts to all three parameters of sterilisation which include proper amount of time, temperature and pressure of the sterilizer.  They have been correlated to the performance of a biological indicator when used according to the manufacturers conditions noted on the label.
- Test must be dated and labeled Once removed from the steriliser the test pack opened, BI labeled, crushed and incubated in the incubator Records of time, date of incubation and staff initials is required and then time and date and initials of the staff reading the final BI result Biological indicators (BI) contain the spores of the bacterium Geobacillus stearothermophilus. Commercially-available spore strips or vials containing the spores are strategically placed in the load to be sterilised. After a cycle, the BI are cultured or evaluated for growth and they must all indicate no growth to declare the sterilisation process a success. In Europe- not daily â every 400 charges or every 6 months. Validation of sterilsers used instead.
- Fumigation is done by two methods: 1. Electric boiler method- 500 ml of formaldehyde (40%) added to distilled water in electric boiler. When the water heats fumes are generated. 2. Potassium permanganate â heat is induced by oxider action of potassium permanganate. 500ml of formaldehyde is added to potassium permanganate which reacts and generates fumes
- Diamond and carbide burs: After use they are placed in 0.2% gluteraldehyde and sodium phenate (Eg. Sporicidin) for at least 10 minutes, cleaned with a bur brush or in an ultrasonic bath. Sterilize in an autoclave or dry heat ďľ Steel burs: May get damaged by autoclaving. Can be sterilized by using a chemical vapor sterilizer or glass bead sterilizer at 2300C for 20-30 seconds.
- Sterilising/disinfecting by other methods (autoclaving, boiling, alcohol-soaking) are not recommended. Glutaraldehyde has been taken off the market since May 2002. It was never intended to be a suture soaking solution due to its high toxicity and the inability to ensure that all the solution is rinsed off before use
- Glass Bead or salt sterilizer is the best option, but they do not sterilize the handle. ⢠Sterilization achieved in 10 seconds ⢠Dry heat is used, with instruments in closed metal or perforated metal boxes. ⢠Sterilization achieved at 218oC for 15 seconds ⢠Gutta percha points are pre-sterilized. ⢠Contaminated points are sterilized by 5.25% sodium hypochlorite.(1 min immersion). ⢠Then rinse with hydrogen peroxide & dry it.
- Steam sterilization should not be used as it results in contamination of surfaces with organic substances Dry heat sterilization also leaves organic and inorganic surface residue Radio frequency glow discharge technique (RFGDT) or Plasma cleaning is used. ďľ In this, material to be cleaned is bombarded by high energetic ions formed in gas plasma in a vacuum chamber. ďľ Removes both organic and inorganic contaminants.
- Failure to sterilise or disinfect reusable medical devices properly may spread infections The type and level of device decontamination depends upon the nature of the item and its intended use
- Those responsible for processing contaminated items must be fully trained and wear protective clothing when necessary Clearly written policies and procedures must be available on-site for training personnel and for monitoring their performance