How to Sterilize Medical Instruments

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Until recently, the most advanced sterilization technology was found only in large hospital sterilizers. There is now a growing demand for more sophisticated sterilization technologies in various professions. By following a few simple steps, you can have clean, sterilized instruments that can be used in any medical setting.

Method 1
Method 1 of 6:

Preparing the Instruments for Decontamination before Sterilization

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  1. Instruments that have been used need to be collected and removed from the area where they were used. Take them to the decontamination area, such as the central processing department (CPD) or sterile processing department (SPD). [1] This will help reduce the chances of contaminating any personal areas or other surfaces within the workspace.
    • The contaminated instruments should be placed and sealed in a plastic container with a lid marked with an approved biohazard label, and then placed in a larger plastic container labeled with a biohazard label. [2]
  2. Before handling any contaminated instruments, you need to be dressed for the part. Workers in areas that decontaminate instruments should wear protective clothing, such as a scrub suit. You also need medical gloves, disposable hair caps, or some other hair covering. [3]
    • If you will be exposed to blood and contaminated fluids, you need to wear a face mask, gown, and eye protection, such as goggles or a full-length face shield. [4]
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  3. 3
    Clean instruments immediately after use. Instruments must be cleaned immediately after use and before you attempt to sterilize them—cleaning the instruments is not the same as sterilizing them. [5] Remove inorganic and organic debris from the instruments with a soft brush and manufacturer-approved detergent. [6] Scrub each instrument well to remove all residual matter, such as blood or organic tissue. If the instrument is hinged, open it using stringers, racks, or instrument pegs so you can clean it thoroughly. [7]
    • If instruments are not cleaned before sterilization, it can increase the difficulty of decontamination and significantly prolong instrument turnover time. [8] Improperly sterilized equipment may also infect patients. [9]
    • There are specialized enzymatic detergent solutions approved for soaking instruments. Your facility will have them on hand with proper instructions for their use. [10]
    • There are automatic washers to facilitate cleaning and decontamination, such as ultrasonic cleaners, but their use depends on the facility and type of equipment.
  4. After scrubbing, run the instruments under pressured water to ensure all debris is gone. This helps remove soil and debris from internal channels that can’t be brushed. [11]
    • Again, cleaning the instruments is not meant to sterilize them. This step just prepares them for sterilization. Sterilization will destroy all germs on the surface of the instrument, lowering the risk of disease. [12]
    • Use caution when handling sharp items, like scissors, blades, and other sharp implements.
    • If an instrument is disposable, dispose of it properly and do not try to wash and reuse it. [13] Some instruments may be packaged in sterile bags, but are not considered disposable themselves.
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Method 2
Method 2 of 6:

Preparing the Instruments for an Autoclave

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  1. Inspect every instrument to make sure it’s clean. Arrange the instruments based on their usage and where they need to end up. Keeping them organized is essential because each instrument has a purpose. Ensure you know what the instruments will be used for before sorting them, and follow the guidelines provided by the Association for the Advancement of Medical Instrumentation (AAMI). [14]
    • Items that should not be autoclaved include: Oils and waxes, some plastics, flammable and radioactive materials, substances that may emit toxic fumes, and samples containing solvents. [15]
  2. Once you have your instruments sorted, place them in sterilized pouches that can be put into the autoclave. You can use special autoclave pouches designed to withstand the high temperatures of the autoclaves. The pouches have a strip of test tape that changes color when the autoclave process is effective. Take each pile of the sorted instruments and wrap them in the pouches, avoiding any tenting and gapping. [16]
    • You shouldn’t have too many instruments in a bag because it could hinder the sterilization process. Ensure that any hinged instrument, such as scissors, is left open when you put it into a pouch. The inside of the instrument needs to be sterilized as well. [17]
    • Autoclaving in pouches is convenient because you can see the instruments, verify what’s inside, and check for any damage to the pouch. [18]
  3. Once you have the instruments locked in a pouch, you need to label each one in case of a processing or sterilization failure. Write the sterilizer used, the cycle or load number, the date of sterilization, and the expiration date (if applicable). [19] Seal each bag securely. If the bag doesn't already have a test strip, attach one. This will show whether the sterilization was successful. Ensure the drain strainer at the bottom of the autoclave’s sterilizer chamber is clean before loading the pouches in the autoclave. [20]
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Method 3
Method 3 of 6:

Sterilizing the Instruments in an Autoclave

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  1. Autoclaves use high-temperature steam emitted at high pressure over a specific time period to sterilize medical instruments. This works by killing the microorganisms through time, temperature, steam, and pressure. [21] There are several different settings on an autoclave machine. For most wrapped instruments, you can use the pre-vacuum cycle. However, always follow the instrument manufacturer’s written instructions for use. Autoclaving on the gravity cycle will sterilize glassware. [22]
    • For unwrapped medical instruments, use the gravity cycle. For liquids, use the liquid cycle.
  2. You need to place your instrument pouches on their edges, using a pouch rack, and onto trays that go into the autoclave machine. Stack them in a single row and ensure they do not overlap so steam can penetrate the instruments in each bag. If you decide to lay pouches flat on the middle to upper trays, leave space between them for proper sterilization. [23]
    • Never lay pouches flat on the bottom tray. This can trap heat and damage the pouch or instruments inside.
  3. Leave approximately 1 inch (2.5 cm) of space between each tray in the autoclave to permit steam circulation. Don't overload the sterilizer trays. Overloading will cause inadequate sterilization and drying. You should also ensure the instruments don’t shift and overlap when you set them inside the machine. Place any empty canisters upside-down to prevent the accumulation of water. [24]
  4. The autoclave machine should run for a certain time period at a specific temperature and pressure. Depending on the packaging and sterilizer type, most autoclave cycles use 30 minutes at 121°C (250°F) in a gravity displacement sterilizer or 4 minutes at 132°C (270°F) in a prevacuum sterilizer. [25] Once the cycle is complete and the pressure gauge is “0,” open the door slowly to let steam out. Then, leave the instrument pouches in the autoclave until they’re completely dry. [26]
    • Drying should take about 30 additional minutes.
  5. After they are finished drying, take the trays of pouches out of the autoclave with sterile tongs and check the indicator tape on the pouches. If the tape changes color according to the manufacturer’s instructions, it means it is sterilized. If the tape does not change color, then the load needs to be re-autoclaved in another autoclave. [27]
    • If the tape changes color, place the pouch on a surface padded with sterile paper or fabric until it’s cool. [28] Once they are cool, store the pouches in a clean, dust-free location at room temperature (about 59ËšF (15ËšC) to 77ËšF (25ËšC)), away from fluorescent or ultraviolet light. Depending on storage conditions, the package should be sterile for 6 months. [29]
  6. Keep a record in a log sheet, using information such as the printed name or initials of the operator, the date the instruments were sterilized, the length of the cycle, the maximum temperature of the autoclave, the amount of waste treated, and the results. [30] For example, note if the indicator strip turned color or if you ran a biological control. Make sure to follow your company’s protocol and document each autoclave operation for as long as you are required.
  7. A biologic control run is essential to determine if the sterility process is adequate. Place a test vial of the bacteria Geobacillus stearothermophilus in the center of a pouch or on a tray in the autoclave. Next, perform a normal operation. This will test to see if the sterilization cycle parameters are sufficient to kill the test microorganisms. [31]
  8. Put the autoclaved vial in a microbiological incubator set at 130ËšF (59ËšC) to 140ËšF (60ËšC) for 24 hours, depending on the manufacturer’s protocols. Compare this to another control vial at room temperature that was not run in the load. The product inside the non-autoclaved vial should turn yellow to indicate bacterial growth. If not, there may be a problem with the sample vial. If that is the case, repeat the testing. If it still doesn’t change color, it may be a bad batch of vials, and you may need a whole new set. [32]
    • If there is no bacterial growth on the autoclaved vial after 24 hours, then sterilization is complete. If you see yellow on the test vial, sterilization has failed. Run the test again and discontinue normal use of the autoclave. If the second test fails again, post a sign that says “Autoclave Not In Use” and contact the manufacturer.
    • This test should be run at least weekly to monitor sterilizers. [33]
    • The spore test should be placed in the center of the autoclave. Be aware that testing standards may vary. [34]
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Method 4
Method 4 of 6:

Sterilizing Equipment with Ethylene Oxide

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  1. Ethylene Oxide (EtO) is used for items that are moisture and heat-sensitive, such as devices with plastic or electrical components that cannot withstand high temperatures. EtO helps perform antimicrobial sterilization to protect instruments from making people sick. Studies prove that EtO is a critical sterilization technology for medical devices. [35] EtO’s uses include sterilizing certain heat-sensitive and irradiation-sensitive materials, as well as some instruments and devices on-site in hospitals. EtO is a colorless gas that kills all microorganisms, leading to the sterilization of the item. [36]
  2. When using ethylene oxide as a cleaning option, the process has five stages—preconditioning and humidification, gas introduction, exposure, evacuation, and air washes. [37] Before sterilization, medical devices are pre-conditioned using heat and humidity for optimal processing. [38]
  3. After the preconditioning stage, the medical devices are loaded in the processing chamber, and EtO enters the chamber from an ancillary source. The EtO gas saturates the process, leading to sterilization. [39] The sterilization cycle alone lasts about 2½ to 3½ hours. [40] The temperature control is the most important. If the temperature falls below the sterilization level, you have to restart the process. The vacuum and pressure of the machine are also important. The machine will not start without the perfect conditions.
    • Towards the end of this phase, the batch report is produced, telling the operator if there are any issues with the process. [41]
    • If the machine is set to auto mode, it will move onto the next stage if the report shows no errors.
    • If there are errors, the machine automatically stops the process so the operator can fix it before any further sterilization is done.
  4. During this stage, any leftover EtO particles are removed from the chamber and destroyed. [42] This is important because EtO gas is extremely flammable and harmful to humans. You must ensure the removed gas is destroyed in an environmentally responsible manner so you, other lab workers, and patients are not harmed. This is also completed under temperature control of 50 to 60ËšC. [43]
    • EtO is a highly toxic substance. Any operator, personnel, and patients who may come into contact with the gas must be aware of the hazards. [44]
    • EtO sterilization takes longer than autoclave sterilization.
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Method 5
Method 5 of 6:

Performing Sterilization by Dry Heat

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  1. Dry heat is a process used on materials that might be damaged by moist heat or that are impenetrable to moist heat, like petroleum, powders, and sharp instruments. It is used to kill microorganisms slowly and is typically done in an oven. There are two types of dry heat stabilizers—the static-air stabilizer and the forced-air stabilizer. [45]
    • The static-air type (or oven-type) is a much slower process. It takes longer to raise the temperature of the air in the chamber to sterilization levels because it has coils that heat up.
    • The forced-air type (or mechanical convection type) uses a motor that circulates the air inside the oven at high velocity.
  2. Similar to autoclaving, begin the dry heat method by washing your hands and putting on non-sterile gloves. Next, wash the instruments to remove any debris or matter that might be left behind. This ensures the items placed into the ovens are as clean as possible and will not have non-sterile materials left behind on them. [46]
  3. Just like with autoclaving, the medical instruments are placed into bags during the sterilization process. Place the cleaned instruments into sterilization pouches. Seal each pouch so it is airtight. This is important because wet or damaged packages will not be sterilized during the process. Ensure the bags have temperature-sensitive tape or an indicator strip. If they don’t, add one. [47]
    • The tape helps you ensure the products are sterilized by reaching the necessary temperature for sterilization.
  4. Once you have all the instruments in pouches, load the pouches into the dry heat oven. Do not overload the oven because the tools will not be sterilized correctly. Once the pouches are loaded, close the door and start the cycle. Periodically check the digital display to ensure the chamber has reached and maintains the right temperature. [48]
    • Follow the manufacturer’s guidelines for loading the ovens.
    • After the cycle is complete, remove the instruments. Check the indicator strips to make sure the items were sterilized. Once the tools are dry, store them in a safe, clean, dry place to protect them from dust and dirt.
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Method 6
Method 6 of 6:

Using Alternative Methods

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  1. Microwaves are also used for disinfecting soft contact lenses, dental instruments, dentures, milk, and urinary catheters for intermittent self-catheterization. Studies show that microwaves completely inactivate bacterial cultures, mycobacteria, viruses, and G. stearothermophilus spores within 60 seconds to 5 minutes, depending on the organism. [49]
    • You can also use this method at home to sterilize baby bottles, as long as you follow the manufacturer’s instructions. [50]
  2. Hydrogen peroxide in the form of a gas plasma or vapor can be used for sterilization. The plasma is made into a cloud of hydrogen peroxide with the help of a strong electric or magnetic field. The sterilization phase of hydrogen peroxide consists of two phases, the diffusion phase and the plasma phase. [51]
    • For the diffusion phase, put the non-sterile object into a vacuum chamber where hydrogen peroxide vapor is diffused for 50 minutes. [52]
    • In the plasma phase, an electrical phase created by radio frequency is applied to the chamber, creating a gas plasma. This help sterilize the product and takes about 75 minutes.
  3. Ozone gas is a gas generated from oxygen and is used to sterilize medical supplies. The ozone method of sterilization is a newer method that involves a lower temperature. With help from a converter, the oxygen from a hospital source is converted into ozone. To sterilize, a concentration of ozone gas is continually pumped through the chamber holding the supplies. [53]
    • The cycle time is about 4 hours and 15 minutes, with a temperature of 30 to 35°C.
  4. Chemical solutions can be used to sterilize instruments by soaking in the solution for the required period of time. [54] The chemical agents are peracetic acid, formaldehyde, and glutaraldehyde. [55]
    • When using any of these chemicals, remember to work in a well-ventilated area with gloves, eye cover, and gowns or aprons for your own protection.
    • Peracetic acid (0.26%) should soak the products for 20 to 30 minutes to kill strains of mycobacteria.
    • Glutaraldehyde (2%) requires a minimum of 20 to 45 minutes of soaking. [56]
  5. Formaldehyde steam is used for products that cannot stand high heat without warping and other damage. In this process, the initial vacuum process removes the air from the chamber. The instruments are loaded, and then the steam is let into the chamber. The vacuum continues to remove the air from the chamber as it heats up. Formaldehyde gases are then mixed with steam and pulsed into the chamber. The formaldehyde is slowly released from the chamber and replaced with steam and air. [57]
    • The conditions have to be ideal for this process, with a relative humidity of 75% to 100% and temperatures between 60 and 80°C.
    • The formaldehyde steam sterilization system has not been FDA-cleared for use in healthcare facilities.
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      Warnings

      • Be sure that instruments of dissimilar metals, such as stainless steel and carbon steel, are separated. Carbon steel instruments should be bagged or placed on autoclavable towels and not directly on stainless steel trays. Mixing will result in oxidation and prevent instruments from being properly sterilized. [58]
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      • Check the manufacturer’s instructions for the proper procedure on sterilization. It can provide specific information on sterilization temperature and time.
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      • If a faulty condition exists (i.e., the sterilizer did not finish the cycle, or water leaks out when the door is unlocked), inform the person responsible for contacting the autoclave service technician. [59]
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      References

      1. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/sterilizing-practices.html
      2. ↑ https://www.osha.gov/laws-regs/standardinterpretations/2013-01-31-2
      3. ↑ https://www.martinsoncollege.com/blog/post/sterile-processing-technicians-what-do-they-wear-at-work
      4. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/sterilizing-practices.html
      5. ↑ https://pmc.ncbi.nlm.nih.gov/articles/PMC11175864/
      6. ↑ https://www.aao.org/education/clinical-statement/guidelines-cleaning-sterilization-intraocular
      7. ↑ https://www.dshs.texas.gov/sites/default/files/IDCU/health/Healthcare-Safety/Conferences/2019/Marrs-OR-to-CSD-Best-Practice-Presentation-DSHS.pdf
      8. ↑ https://pmc.ncbi.nlm.nih.gov/articles/PMC11175864/#R8
      9. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/healthcare-equipment.html
      1. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/sterilizing-practices.html
      2. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/cleaning.html
      3. ↑ https://www.cdc.gov/hygiene/pdf/331782-a_cleaning_sanitizing_disinfecting_508.pdf
      4. ↑ https://www.cdc.gov/dental-infection-control/hcp/dental-ipc-faqs/single-use-devices.html
      5. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/sterilizing-practices.html
      6. ↑ https://medicine.buffalo.edu/offices/facilities/services/autoclave/operating-procedure.html
      7. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/steam-sterilization.html
      8. ↑ https://www.aorn.org/outpatient-surgery/article/2003-May-instrument-sterilization-guide
      9. ↑ https://pmc.ncbi.nlm.nih.gov/articles/PMC6089051/
      10. ↑ https://www.cdc.gov/dental-infection-control/hcp/summary/sterilization-disinfection.html
      11. ↑ https://medicine.buffalo.edu/offices/facilities/services/autoclave/operating-procedure.html
      12. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/steam-sterilization.html
      13. ↑ https://biology.ucsd.edu/administration/units/safety/training/autoclave.html#which-autoclave-cycle-should-i-select
      14. ↑ https://youtu.be/_gLqsuSk8y0?t=31
      15. ↑ https://sharedresearchfacilities.wvu.edu/files/d/d26b4ee5-86e3-45f2-8570-ae81249e5ef4/bnrf_autoclave-esb-sop-20140413.pdf
      16. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/steam-sterilization.html
      17. ↑ https://www.aorn.org/outpatient-surgery/article/2003-May-instrument-sterilization-guide
      18. ↑ https://drs.illinois.edu/Page/SafetyLibrary/autoclavesafetyandoperation
      19. ↑ https://www.aorn.org/outpatient-surgery/article/2003-May-instrument-sterilization-guide
      20. ↑ https://www.cardinalhealth.com/content/dam/corp/web/documents/Manual/cardinal-health--sterilization-pouches-instructions-for-use.pdf
      21. ↑ https://medicine.buffalo.edu/offices/facilities/services/autoclave/operating-procedure.html
      22. ↑ https://drs.illinois.edu/Page/Waste/AutoclaveWasteAndValidation
      23. ↑ https://ehs.ucr.edu/sites/default/files/2019-04/autoclave_testing_packet_20150325.pdf
      24. ↑ https://www.cdc.gov/dental-infection-control/hcp/dental-ipc-faqs/sterilization-monitoring.html
      25. ↑ https://www.cencalhealth.org/wp-content/uploads/2021/10/hsfacilityautoclavebioindicator201608.pdf
      26. ↑ https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/sterilization-medical-devices
      27. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/ethylene-oxide-sterilization.html
      28. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/ethylene-oxide-sterilization.html
      29. ↑ https://www.advamed.org/wp-content/uploads/2019/11/infographic-eto-sterilization-and-medical-devices.pdf
      30. ↑ https://www.advamed.org/wp-content/uploads/2019/11/infographic-eto-sterilization-and-medical-devices.pdf
      31. ↑ https://www.eventreg.purdue.edu/info/central-service/pdf/CIS304.pdf
      32. ↑ https://www.eurotherm.com/life-sciences-cpg-processes-applications/ethylene-oxide-eto-sterilization-process/
      33. ↑ https://www.advamed.org/wp-content/uploads/2019/11/infographic-eto-sterilization-and-medical-devices.pdf
      34. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/ethylene-oxide-sterilization.html
      35. ↑ https://www.ncbi.nlm.nih.gov/books/NBK589511/
      36. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/other-sterilization-methods.html
      37. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/sterilizing-practices.html
      38. ↑ https://www.usamedicalsurgical.com/blog/benefits-biological-indicators-medical-sterilization-process/
      39. ↑ https://www.bionicsscientific.com/blog/what-is-hot-air-oven-and-how-does-it-work/
      40. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/other-sterilization-methods.html
      41. ↑ https://www.nhs.uk/baby/breastfeeding-and-bottle-feeding/bottle-feeding/sterilising-baby-bottles/
      42. ↑ https://pmc.ncbi.nlm.nih.gov/articles/PMC10608877/
      43. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/hydrogen-peroxide-gas-plasma-file-name.html
      44. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/other-sterilization-methods.html
      45. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/other-sterilization-methods.html
      46. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/chemical-disinfectants.html
      47. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/healthcare-equipment.htm
      48. ↑ https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/other-sterilization-methods.html
      49. ↑ https://array.aami.org/content/news/asked-answered-sterilization-and-metal-on-metal-contact
      50. ↑ https://medicine.buffalo.edu/offices/facilities/services/autoclave/operating-procedure.html

      About This Article

      Article Summary X

      To sterilize medical instruments, start by putting the tools into sterilization pouches and sealing each one so that it’s airtight. Then, load them into a 300° F oven, being careful not to overload the racks. Next, heat the tools for 150 minutes before removing them from the oven. Finally, check the indicator strips on the bags to verify that the tools reached the proper temperature and have been sterilized. To learn how to sterilize instruments using hydrogen peroxide, read on!

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