sterilizers. definition of sterile free of microorganisms (bacteria) bacteria bacteria can be...
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Sterilizers
Sterilizers
Definition of sterile Free of microorganisms (bacteria)
Bacteria
Bacteria can be broken down into two groupsPathogenic - cause diseaseNonpathogenic - do not cause disease
Pathogenic / Nonpathogenic
To make something sterile, we want to destroy ALL bacteria
Bacteria
Some bacteria are “spore forming” which means they have the ability to transform themselves into spores and hibernate for an indefinite period of time
They begin to grow again when placed in a favorable environment (such as the human body)
Spore forming bacteria are extremely durable and a great deal of effort is necessary for their destruction
Bacteria (Continued)
Sterilization is successful in destroying allbacteria because it fools the spore formingbacteria out of hibernation by giving it two ofthe three conditions necessary for growthCorrect temperatureMoisture
Once bacteria starts to grow and reproduce, it iseasy to destroy
Sterilizing vs. Sanitizing
Sanitizing is the process of cleaning something
A dishwasher sanitizes dishes by killing most of the bacteria but not all, so the item cannot be considered sterile
Sanitizing an item is not effective for killing spore forming bacteria
What is sterile?
There is no way we can measure all products being sterilized to ensure that every organism has been destroyed
Instead, a standard has been established that uses probabilities
Sterile
An item is considered to be sterile when:All the conditions necessary for sterilization are
presentAnd the probability is that no more than 1 in 1
million microorganisms survived
This is the present standard used in the United States for labeling a product “sterile”
The ideal sterilant would
Destroy all types of microorganisms including viruses, bacteria and fungiNot adversely affect medical instrumentsAct rapidly, allowing use of the instruments again as soon as possiblePenetrate thoroughly enough to ensure sterilization of even the most inaccessible surfacesDiffuse through barrier packaging, allowing sterilization of the instruments without risk of recontamination after sterilization
The ideal sterilant would (Continued)
Be non-hazardous to humans, non-flammable and non-explosiveLeave no residue after sterilization which couldharm the patientBe readily available, easy to store and useBe inexpensiveUnfortunately, since no single agent meets all ofthese criteria, healthcare facilities must utilize arange of sterilization methods to meet their needs
Methods of Sterilization
Based on several factors such as cost, type ofmaterial to be sterilized, and size of the material to be sterilized, overview of methods; FlameChemical AgentsGamma RadiationEthylene Oxide (ETO)PlasmaHeat
Heat
The most widely used method of sterilizationIf a microorganism is exposed to the rightamount of heat for the right amount of time, thatmicroorganism will be destroyedThe method of heat being used will have an important impact on the sterilization timeTwo types of heatDry HeatMoist Heat
Dry Heat Sterilization
Works much like an oven
“Cooks” the microorganism at temperatures around 420°F for 3 to 5 hours
Moist Heat Sterilization
The most widely used because microorganisms are most easily killed by moist heat
The most common type is the steam pressureSterilizer
The most cost effective method of sterilization
The greater the pressure the greater the temperature
Moist Heat Sterilization (Continued)
Sterilization is achieved by injecting steam, under pressure, into the sterilizer chamber
The increase in pressure causes a corresponding increase in temperature
Once the necessary temperature for sterilization has been achieved we stop injecting steam
Sterilization
Sterilization is achieved by ensuring that thefollowing conditions exist in the chamberCorrect temperature Time
Basic Steam Sterilizers
High Vacuum Sterilizers (Autoclave)Rely on electrical pumps or mechanical devices
to produce a high vacuum in the chamber
This vacuum removes air from the chamber
This is to ensure all air has been removed from the packages so that steam will penetrate well
Basic Steam Sterilizers (Continued)
Gravity SterilizersUses steam entering from the top of the
chamber to drive the relatively cold air out through the bottom of the chamber and drain
Generally used for smaller packages that do notcontain much air
While it is not a “vacuum sterilizer” a vacuum can still be drawn in the chamber
Basic Steam Sterilizers (Continued)
AutoclaveSettings
Temp(F)
Pressure(PSI)
Time(MINS)
Wrapped Items
250 20 30
Bottles Solutions
250 20 30
Flashing 270 30 4-7
Washer Sterilizers
Uses the same sterilization procedures as asteam sterilizer but has the capability to wash the instruments before they are sterilized
These larger versions of sterilizers are usuallyfound in the Central Sterile Section (CSS)
Major Components of a Steam Sterilizer
JacketChamber
Major Components of a Steam Sterilizer(Continued)
Jacket The outer shell and narrow sealed space
surrounding the inner compartment (chamber)Has two functions:
Fills with steam and acts as a reservoir for thechamber steamHelps preheat and regulate the chamber temperature
Major Components of a Steam Sterilizer(Continued)
Chamber The inner compartment where the items to be
sterilized are placed The door is sealed with a gasket to prevent the
steam from escapingAt 30 PSI of chamber pressure, a door that
measures 20” X 20” will have 12,000 pounds of pressure on it’s inner surface
Common Supporting Utilities
Electricity220 VAC, 3-Phase used for steam generator
heater operation and vacuum pumps on larger sterilizers
110 VAC is used for sterilizer controlWaterEvery steam sterilizer uses waterWater must be within the pressure range stated
and must flow at the necessary volume required by the manufacturer’s specifications
Common Supporting Utilities (Continued)
Poor water supply can lead to poor vacuum which leads to wet packages
SteamMust be in the correct range of pressure,
volume and moisture content Low pressure may cause a failure to reach
temperatureHigh pressure may cause an over temperature
condition and may damage plumbing components
Common Supporting Utilities (Continued)
Steam Typical moisture content is about 97% saturated
Steam
Too much saturation may lead to wet packages
Steam pipes should be well insulated, dry, and away from cold areas such as air conditioning piping or the ground
PressureMeasured in two ways:Dynamic Static
Dynamic pressureDynamic pressure is pressure in the line when the substance (air, water, steam) is flowing
Static pressureStatic pressure is the pressure in the line whenthere is no movement of the substance in theline; is generally lower than dynamic pressure
Vacuum and Pressure
Vacuum is pressure less than 1 atmosphere
Molecules move farther apart – means free path
The Plasma Sterilization Process is a vacuumprocess of: Low Temperature Plasma Low Thermal Transfer Faster Diffusion Rates
Atmospheric Pressure
1 Atmosphere = 760 mm of Hg1 Torr = 1 mm of Hg1 Torr = 13.3 Pascal
Low Thermal Transfer
Thermos Bottle2 degree rise in 24 hours Load at 20 degrees CentigradeWalls at 45 degrees Centigrade
Diffusion
Microwave popcorn aromaDiffusion is limited by collisionsVacuum has fewer collisionsH2O2 must diffuse from injection valve into load
Water
Higher in the mountains, water boils at lowerTemperaturesLower pressure = lower boiling temperatures
Quality AssuranceIndicators of SterilizationRecorders and PrintersVerification of Sterilization
Indicators of SterilizationTest packsUsed to determine if the product being sterilized
has in fact been sterilized Indicators of sterilization
Does not indicate that sterilization has taken place
Indicators of Sterilization (Continued)
Designed to indicate that certain conditions necessary for sterilization are presentAutoclave TapePlaced on the outside of packages to hold
them together and show exposure to heat The tape has strips that will darken when
heated The tape only indicates that the outside of the
package was exposed to heat
Indicators of Sterilization (Continued)
Diac Small glass tube with a chemical pellet inside that
melts and turns to a dark color when exposed to the right amount of heat
Placed in the center of surgical packs to assure the user that the inside of the package was exposed to heat
Indicators of Sterilization (Continued)
“Bowie-Dick”/”Check-a-Clave” Sheets Sheets of specially prepared paper that turn dark
when exposed to heat in a vacuumPlaced inside test packs to determine if high
vacuum sterilizers are removing the air from the package
Failure of this test indicates a malfunction of the vacuum system, i.e. Leak
These sheets are only used in high vacuum sterilizers
Recorders and Printers (Continued)
Used to keep a permanent record of eachsterilization cycleRecorders The older style deviceUses a round paper disk and an ink pen to record
temperature as the disk makes a complete revolution
One complete revolution indicates a 24 hour period and then is replaced
Can be difficult to read and the recorder itselfrequires frequent maintenance
Recorders and Printers (Continued)
PrintersRecords more data than recorders and no
interpretation is requiredPrints the status of the sterilizer in every phase of
SterilizationInformation may include the sterilizer number,pressures, temperatures, type of cycle, and alarms
Requires very little maintenance
Verification of Sterilization
The only method that actually proves that sterilization has taken place involves killing live organismsThe two most common forms of this test Spore strip “A-test”
Spore Strip and “A-test”
These are spores of non-pathogenic bacteria in a container which is placed inside a test pack and sterilizedAfter sterilization the spores are placed in anincubator to provide the correct temperature, moisture, and nutrition necessary for growthIf no growth occurs after the required time (2 to 7 days) sterilization has been provenThis test is usually performed once a day forsteam pressure sterilizers and for every load on agas sterilizer