Sterilizers

 Definition of sterile  Free of microorganisms (bacteria) Bacteria  Bacteria can be broken down into two groups  Pathogenic - cause disease  Nonpathogenic - 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 all bacteria because it fools the spore forming bacteria out of hibernation by giving it two of the three conditions necessary for growth  Correct temperature  Moisture  Once bacteria starts to grow and reproduce, it is easy 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 present  And 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 fungi  Not adversely affect medical instruments  Act rapidly, allowing use of the instruments again as soon as possible  Penetrate thoroughly enough to ensure sterilization of even the most inaccessible surfaces  Diffuse 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-explosive  Leave no residue after sterilization which could harm the patient  Be readily available, easy to store and use  Be inexpensive  Unfortunately, since no single agent meets all of these criteria, healthcare facilities must utilize a range of sterilization methods to meet their needs

Methods of Sterilization  Based on several factors such as cost, type of material to be sterilized, and size of the material to be sterilized, overview of methods;  Flame  Chemical Agents  Gamma Radiation  Ethylene Oxide (ETO)  Plasma  Heat

Heat  The most widely used method of sterilization  If a microorganism is exposed to the right amount of heat for the right amount of time, that microorganism will be destroyed  The method of heat being used will have an important impact on the sterilization time  Two types of heat  Dry Heat  Moist 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 pressure Sterilizer  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 the following conditions exist in the chamber  Correct 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 Sterilizers  Uses 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 not contain much air  While it is not a “vacuum sterilizer” a vacuum can still be drawn in the chamber

Basic Steam Sterilizers (Continued) Autoclave Settings Temp (F) Pressure (PSI) Time (MINS) Wrapped Items Bottles Solutions Flashing

Washer Sterilizers  Uses the same sterilization procedures as a steam sterilizer but has the capability to wash the instruments before they are sterilized  These larger versions of sterilizers are usually found in the Central Sterile Section (CSS)

Major Components of a Steam Sterilizer  Jacket  Chamber

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 the chamber steam  Helps 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 escaping  At 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  Electricity  220 VAC, 3-Phase used for steam generator heater operation and vacuum pumps on larger sterilizers  110 VAC is used for sterilizer control  Water  Every steam sterilizer uses water  Water 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  Steam  Must be in the correct range of pressure, volume and moisture content  Low pressure may cause a failure to reach temperature  High 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

Pressure  Measured in two ways:  Dynamic  Static Dynamic pressure  Dynamic pressure is pressure in the line when the substance (air, water, steam) is flowing Static pressure  Static pressure is the pressure in the line when there is no movement of the substance in the line; 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 vacuum process of:  Low Temperature Plasma  Low Thermal Transfer  Faster Diffusion Rates

Atmospheric Pressure  1 Atmosphere = 760 mm of Hg  1 Torr = 1 mm of Hg  1 Torr = 13.3 Pascal Low Thermal Transfer  Thermos Bottle  2 degree rise in 24 hours  Load at 20 degrees Centigrade  Walls at 45 degrees Centigrade

Diffusion  Microwave popcorn aroma  Diffusion is limited by collisions  Vacuum has fewer collisions  H2O2 must diffuse from injection valve into load Water  Higher in the mountains, water boils at lower Temperatures  Lower pressure = lower boiling temperatures

Quality Assurance  Indicators of Sterilization  Recorders and Printers  Verification of Sterilization Indicators of Sterilization  Test packs  Used 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 present  Autoclave Tape  Placed 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 vacuum  Placed 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 each sterilization cycle  Recorders  The older style device  Uses 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 itself requires frequent maintenance

Recorders and Printers (Continued)  Printers  Records more data than recorders and no interpretation is required  Prints the status of the sterilizer in every phase of Sterilization Information 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 organisms  The 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 sterilized  After sterilization the spores are placed in an incubator to provide the correct temperature, moisture, and nutrition necessary for growth  If no growth occurs after the required time (2 to 7 days) sterilization has been proven  This test is usually performed once a day for steam pressure sterilizers and for every load on a gas sterilizer