Sterilization

4-H Veterinary ScienceExtension Veterinary Medicine 

Texas AgriLife Extension ServiceCollege of Veterinary Medicine and Biomedical Science

Texas A&M Systemhttp://aevm.tamu.edu

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

Microorganisms Invisible Cause infections

Sterilization Destruction of all microorganisms

Disinfectant Destruction of harmful organisms, or

pathogens on nonliving objects

Disinfectants Types of disinfectants

Bactericides Fungicides Germicides Virucides

All prevent transfer of infection

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

Sterilizing Agents

Type of agents Chemical Physical

Moist heat Dry heat

Most clinics use physical agents

Steps for Chemical SterilizationStep 1

Decontaminate, 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

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

Dry heat Slow sterilizer Higher temperatures Penetrates

Oil-based materials Closed containers

Steps of Dry-Heat SterilizationStep 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.

Direct flame Can damage the exposed object

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

Other Sterilization Technology

Filtration Ultraviolet irradiation Cold sterilization Ethylene oxide

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

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

Cold sterilization Gamma radiation Kill microorganisms without a rise in

temperature Highly successful in sterilizing

Syringes Stitching (sutures) materials Containers

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