Sterilization

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Sterilization

• 4-H Veterinary Science
• Extension Veterinary Medicine 
• Texas AgriLife Extension Service
• College of Veterinary Medicine and Biomedical
  Science
• Texas AM System
• http//aevm.tamu.edu

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Objectives

• Understand and utilize correct sterilization and
  disinfection techniques
• Distinguish between sterilization and
  disinfection
• List the characteristics of an ideal antiseptic
• Describe sterilizing agents and rank their
  effectiveness
• Discuss the time/temperature relationship in
  destroying microorganisms

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• Microorganisms
• Invisible
• Cause infections
• Sterilization
• Destruction of all microorganisms
• Disinfectant
• Destruction of harmful organisms, or pathogens on
  nonliving objects

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• Disinfectants
• Types of disinfectants
• Bactericides
• Fungicides
• Germicides
• Virucides
• All prevent transfer of infection

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• Sterilization
• Antiseptics
• Prevent growth of microorganisms without
  destroying them
• Not harmful to patients
• Characteristics
• Active against pathogens
• Non-irritating
• Cleansing
• Cost-effective
• Long shelf life
• Safe for patient and handler
• Stable in the presence of organic matter

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Sterilizing Agents

• Type of agents
• Chemical
• Physical
• Moist heat
• Dry heat
• Most clinics use physical agents

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• Steps for Chemical Sterilization
• Step 1Decontaminate, clean, and thoroughly dry
  all instruments and other items to be sterilized.
  Water from wet items will dilute the chemical
  solution, thereby reducing its effectiveness.
• Step 2Prepare the glutaraldehyde-containing
  solution (or other chemical solution) by
  following the manufacturer's instructions--or use
  a solution that was prepared previously, as long
  as it is clear (not cloudy) and has not expired.
  After preparing the solution, put it in a clean
  container with a lid. Always mark the container
  with the date the solution was prepared and the
  date it expires.
• Step 3 Open all hinged instruments and other
  items and disassemble those with sliding or
  multiple parts. The solution must contact all
  surfaces in order for sterilization to be
  achieved. Completely submerge all instruments and
  other items in the solution. All parts of the
  items should be under the surface of the
  solution. Place any bowls and containers upright,
  not upside-down, and fill with the solution.
• Step 4Follow the manufacturer's instructions
  regarding the time necessary for sterilization to
  be achieved. In general, if the solution contains
  glutaraldehyde, cover the container and allow the
  instruments and other items to soak for at least
  10-12 hours. (Times vary for different products.
  Follow the manufacturer's instructions.) Do not
  add or remove any items to the solution once
  timing has begun.
• Step 5 Remove the items from the solution using
  large, sterile pickups.
• Step 6 Rinse thoroughly with sterile water to
  remove the residue that chemical sterilants leave
  on items. This residue is toxic to the skin and
  tissues.
• Step 7 Store items properly. Proper storage is
  as important as the sterilization process itself.
  Place the items on a sterile tray or in a sterile
  container and allow to air-dry before use or
  storage. Use the items immediately or keep them
  in a covered, dry, sterile container and use
  within one week.

From www.engenderhealth.org/IP/instrum/inm12.html
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• Moist heat
• Steam and boiling water
• Alone not effective
• Captured steam effective
• Autoclave
• Sealed chamber that furnished both hear and
  pressurized steam for sterilization
• Inexpensive
• Sterilizes
• Instruments
• Syringes
• Needles
• Other materials

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• Dry heat
• Slow sterilizer
• Higher temperatures
• Penetrates
• Oil-based materials
• Closed containers

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• Steps of Dry-Heat Sterilization
• Step 1
• Decontaminate, clean, and dry all instruments and
  other items to be sterilized.
• Step 2
• Either 1) wrap the instruments and other items
  using foil, double-layered cotton, or muslin
  fabric 2) put unwrapped instruments and other
  items on a tray or shelf or 3) place instruments
  and other items in a metal, lidded container.
• Note Because dry-heat sterilization works by
  raising the temperature of the entire item to the
  designated temperature, it is not necessary to
  open or unlock hinged instruments or other items
  or to disassemble those with sliding or multiple
  parts. In addition, instruments and other items
  can be placed in closed containers.
• Step 3
• Place instruments and other items in the oven,
  and heat to the designated temperature. The oven
  must have a thermometer or temperature gauge to
  make sure the designated temperature is reached.
•  
• Use the list here to determine the appropriate
  amount of time to sterilize instruments and other
  items for different temperatures. (do not begin
  timing until the oven reaches the desired
  temperature, and do not open the oven door or add
  or remove any items). The times shown here
  represent the amount of time that items must be
  kept at the desired temperature to ensure that
  sterilization is achieved. Keep in mind that the
  total cycle time--including heating the oven to
  the correct temperature, sterilization, and
  cooling--is usually twice as long as the time
  noted here. 
• Temperature 170 degrees C (340 degrees F) - 1
  hour160 degrees C (320 degrees F) - 2 hours150
  degrees C (300 degrees F) - 2.5 hours140 degrees
  C (285 degrees F) - 3 hoursNote Because dry
  heat can dull sharp instruments and needles,
  these items should not be sterilized at
  temperatures higher than 160 degrees C.
• Step 4
• Leave items in the oven to cool before removing.
  When they are cool, remove items using sterile
  pickups and use or store immediately.
• Step 5
• Store items properly. Proper storage is as
  important as the sterilization process itself
• Wrapped items. Under optimal storage conditions
  and with minimal handling, properly wrapped items
  can be considered sterile as long as they remain
  intact and dry. For optimal storage, place
  sterile packs in closed cabinets in areas that
  are not heavily trafficked, have moderate
  temperature, and are dry or of low humidity. When
  in doubt about the sterility of a pack, consider
  it contaminated and re-sterilize it.
• Unwrapped items. Use unwrapped items immediately
  after removal from the autoclave or keep them in
  a covered, sterile container for up to one week.

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• Direct flame
• Can damage the exposed object

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Time/Temperature Relationship

• Most important factor in destroying
  microorganisms is length of exposure to heat
• Varies with microorganisms
• The higher the temp the faster it will kill
  microorganisms exposed
• Temps lower than boiling point can sterilize some
  medications and milk

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Other Sterilization Technology

• Filtration
• Ultraviolet irradiation
• Cold sterilization
• Ethylene oxide

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• Filtration
• Complete removal of microorganisms and particles
  of a certain size from liquid or gas
• Used by vet personnel in producing sterile and
  particle-free fluids, such as intravenous fluids

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• Ultraviolet irradiation
• Destroys microorganisms in air, liquid, and
  surface
• Germicidal UV radiation is generated by passing
  electricity through mercury vapor in special
  glass tubes
• UV lamps sterilize most effectively in still air
  at room temperature

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• Cold sterilization
• Gamma radiation
• Kill microorganisms without a rise in temperature
  
• Highly successful in sterilizing
• Syringes
• Stitching (sutures) materials
• Containers

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• Ethylene oxide
• Makes possible the use of low cost, plastic
  materials for sterile, disposable medical
  instruments
• Primary gas used in hospitals and clinics to
  sterilize items that cannot withstand steam
  sterilization
• Vapors are hazardous to people