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