Module 9: Sterilization PDF

Module 9: Sterilization Module 9: Sterilization Learning Objectives By the end of this module the student will be able to: 1. Explain the importance of sterilization process validation and medical device compatibility 2. Describe the requirements for steam sterilization and explain how the main parts of a steam sterilizer help to meet these requirements 3. Describe the different types of steam sterilizers and the critical parameters needed for each type. 4. Explain how to manage a steam sterilization cycle 5. Describe the routine maintenance of steam sterilizers 6. Identify the elements of a steam sterilization quality assurance course 7. Explain how to respond to an adverse sterilization event 8. Identify the commonly used methods of low temperature (chemical) sterilization, and the;  critical parameters needed for each method  selection criteria, load management and operating requirements for each method Introduction Module 3 reviewed how the Spaulding Classification System is used to determine the required level of reprocessing that each medical device must undergo in order for it to be safe for patient use. Critical devices such as those that will contact normally sterile body tissue, e.g. surgical instruments, must be sterile when used. A device that is sterile is one that is “free from viable (living) microorganisms”. Sterilization is the process that achieves this state. This module will review the ways in which sterilization can be achieved, and the MDR Technician’s responsibilities during the process of sterilization. 1. Process validation and device compatibility Patient safety requires that any sterilization process being used to sterilize medical devices be effective, and that the medical devices that are being sterilized not be damaged by the process. The terms “sterilization process validation” and “medical device compatibility” are used to describe these two requirements. Sterilization process validation is performed by the sterilizer manufacturer. It is a documented protocol of tests and observations that confirms that a sterilization process is effective i.e. it will kill the viable microorganisms when used under the conditions specified by the manufacturer. The conditions will be carefully described in the sterilizer operator’s manual which is provided by the manufacturer when the sterilizer is purchased, and is often also available on-line. They will include specific requirements for sterilization temperature and sterilization (exposure) time for the various cycles that the sterilizer provides. Medical device compatibility is a device’s ability to withstand the sterilization process and to remain within operating specifications. It is the responsibility of the device manufacturer to determine device © Vancouver Community College 1 Medical Device Reprocessing Theory Modules Module 9: Sterilization functionality after repeated cycles in a specific sterilization process. The device instructions for use (IFUs) will recommend a specific sterilization method including the type of sterilant e.g. steam, hydrogen peroxide vapour, and the exposure time as well as any limitations associated with sterilizing the device by that method. Compatibility applies to sterilization trays and packaging materials as well as medical devices. What all of this means for the technician is that in order to ensure the sterility of every device these instructions for use for both the sterilizer and the medical device must be followed:  Instructions for use from the sterilizer and device manufacturers are incorporated into the routine work instructions for your department.  Technicians responsible for sterilization (or any other aspect of reprocessing for that matter) are educated and trained in the specific reprocessing practices. Learning the theory of MDR practice is important, but every department will have specific ways of doing things, and all staff must follow their department’s procedures/work instructions.  Work instructions are followed without fail—for every device, every time. Skipping a step or adapting a written procedure may place patients at risk. Because steam sterilization is the most common method of sterilization, this module will begin there. 2. Requirements for steam sterilization and the main parts of a steam sterilizer Requirements for steam sterilization Effective steam sterilization depends on a combination of:  Moisture (steam)  Temperature (heat)  Time  Air removal From previous modules you will recall that microorganisms are composed of protein, and that heat will kill microorganisms because it coagulates their proteins. However, dry heat on its own is not particularly effective in killing the microorganisms i.e. it takes a long time to kill microorganisms using dry heat. The time required to kill microorganisms can be reduced by adding moisture and pressure to the heat. That’s what happens during steam sterilization. Moisture Moist heat kills better/faster than dry heat. When moisture e.g. steam, is added to heat, the heat is conducted more efficiently. This means that microorganisms will die more quickly than if they were exposed to dry heat alone. Think of the difference in the time that it takes to boil a potato, compared to baking a potato in an oven. The boiled potato cooks in a shorter period of time thanks to the moist heat. A similar response happens with sterilization. Microorganisms will die more quickly when exposed to moist heat rather than dry heat. © Vancouver Community College 2 Medical Device Reprocessing Theory Modules Module 9: Sterilization Moisture also softens the cell membrane and other protective coverings of microorganisms to make them easier to kill. Steam quality is important in steam sterilization. The ideal steam quality is 3% water and 97% steam. Higher water content may lead to wet loads. Temperature and pressure Heat kills microorganisms. Higher temperatures kill better/faster than lower temperatures. The temperature of steam at sea level, (where the atmospheric pressure is 14.7 psia), is 100°C, the boiling point of water. However, 100°C is not high enough to kill many types of microorganisms, at least within a realistic time frame. The temperature of steam can be increased by putting it under pressure, which is exactly what happens in a steam sterilizer. The relationship between steam pressure and temperature is a scientific fact. It is fixed and predictable. As pressure rises, the temperature of the steam automatically rises. Raising the temperature reduces the time that it takes to kill microorganisms. Steam Pressure Steam Temperature ° 0 psia* psig** C F 15 (14.7) 0 100 212 30 15 121 259 42 27 132 270 *pounds per square inch absolute **pounds per square inch gauge The table above provides an example of how pressure can be measured in two ways. Some sterilizer manufacturers use PSIA (pounds per square inch absolute) for their equipment displays, while other manufacturers use PSIG (pounds per square inch gauge). Sterilizers that use PSIA to measure pressure will base their measurements on a standard atmospheric pressure of 15 PSIA (the atmospheric pressure at sea level, 14.7 psi rounded up to 15). During a cycle as pressure rises, the pressure reading in the chamber will be added to the initial 15 psi to display the numbers that can be seen in the left hand column. In sterilizers that use PSIG, the pressure gauge is calibrated to 0 (instead of the sea level pressure of about 15 psi). As pressure rises during a cycle, the pressure reading that is displayed will be the PSIA pressure minus the 15 psi. This measurement can be seen in the second column from the left in the preceding table. Both systems reflect the relationship between steam under pressure and a corresponding increase in its temperature. They convey the same information but use different scales, much the same as Celsius and Fahrenheit. The understanding of pressure readings will be revisited later in this module. Time Sterilization times can be reduced by adding moisture and pressure to heat. © Vancouver Community College 3 Medical Device Reprocessing Theory Modules Module 9: Sterilization In a busy MDRD, the quicker that sterilization can be achieved the better. Shorter cycles allow more loads to be processed in a set period of time, and make for cost effective use of expensive sterilizers. By adding moisture and pressure to heat, a steam sterilizer can significantly reduce the time that it takes to kill microorganisms. Air removal The presence of air lowers the steam temperature. All air must be removed from the chamber and the load before actual sterilization begins. An important principle of steam sterilization is that air and steam do not mix. Air interferes with sterilization. Any air that is trapped within packages or in the sterilization chamber itself will lower the temperature of the steam, and at a lower temperature, sterilization will not occur. The problem of air trapping is important to your understanding of the types of steam sterilizers, and correct sterilizer loading procedures, both of which will be discussed later in this module. Parts of a steam sterilizer A steam sterilizer addresses the relationships between moisture, temperature (and pressure) and time. It is a complex piece of machinery, but for study purposes, its operation can be simplified. Image 9.1 below shows the basic parts of a steam sterilizer. A cycle begins once the door is locked and a cycle is selected. Steam enters the closed chamber at the top and back of the sterilizer. Air flows out of the chamber through the drain at the bottom front of the sterilizer. The actual sterilization time (exposure time) is measured once all air is removed, and steam under pressure completely fills the chamber. Following sterilization, steam is removed and the chamber is refilled with fresh, filtered air. Image 9.1: Parts of a steam sterilizer (VCC) © Vancouver Community College 4 Medical Device Reprocessing Theory Modules Module 9: Sterilization Chamber The chamber is the vessel in which sterilization takes place. It is extremely strong because it must withstand the pressures of sterilization. The chamber can vary in size from a tabletop model the size of a small breadbox to a built-in floor model that can be 1.5m x 1.5m x 3m or more. Size depends on the requirements of the health care facility. Image 9.2 and 9.3 illustrates two sizes of steam sterilizers. Image 9.3: Table top steam sterilizer (K Scott) Image 9.2: Floor model steam sterilizers (K Scott) Door The door allows access to the chamber. It too, is very strong because, when locked into place, it is part of the chamber. The door is locked throughout the sterilization cycle. It is important that the door be locked securely. If it is not, steam can escape around the edges during sterilization. Should that happen, temperature and pressure may be lost, preventing sterilization from occurring. Most large sterilizer doors have motors to automatically close and lock them. Some sterilizers have a door at either end of the chamber so that packages can be loaded in one side and removed from the other. Some have doors that slide up and down instead of opening outward. Sterilizer doors have a built-in safety feature. Once they are locked and the cycle has begun, they cannot be unlocked until pressure in the chamber has returned to normal. This ensures the effectiveness of the sterilizing process as well as preventing accidents. On the inside edge of the door is a seal. On some sterilizers it is a rubber-like gasket. On others it is an inflatable tube that fills with steam at the beginning of a cycle. When the heavy steel door is locked in place against the steel surface of the sterilizer body, the seal, which is relatively pliable, fills any small gaps that might occur between the 2 metal surfaces. This ensures that the door will be air/steam-tight when it is locked in place. Jacket A steel jacket surrounds the chamber of the sterilizer. It is separated from the chamber by a space of about 7.5cm to 10cm. Steam at a sterilizing temperature (i.e., 132o C) continuously circulates within this space, even between sterilizing cycles when the unit is not in use, as long as there is a supply of steam available. © Vancouver Community College 5 Medical Device Reprocessing Theory Modules Module 9: Sterilization Steam in the jacket does two things. It heats the chamber walls, preventing the condensation that would occur at the start of a cycle when steam coming into the chamber contacts the otherwise cool chamber walls. The steam in the jacket also maintains a supply of steam ready to enter the chamber immediately. A cycle can begin as soon as it is selected by the operator, rather than be delayed as would be the case if steam had to flow from a remotely located boiler. The outside of the jacket is covered with insulation to prevent condensation from forming on the jacket wall. Baffle The baffle is a metal plate or nozzle located at the steam inlet into the chamber. It deflects steam as it enters the chamber, helping to distribute it evenly throughout the chamber. If steam were not deflected, the packages near the steam inlet would become wet from the continuous flow of steam over them. Those packages would not dry at the end of the cycle, and consequently would be considered contaminated and could not be used. Drain or Air Outlet The drain or air outlet provides a path for air to flow out of the chamber at the beginning of a sterilization cycle in the same way in which water flows through a sink drain. Sterilization cannot begin until all air is gone from the chamber. At the end of the sterilization phase, it also serves as an outlet for the steam that is in the chamber. Without an outlet, air and steam removal could not occur. The sterilizer’s thermometer is located in the drain line. This is the coolest point in the system. If the temperature in the drain line meets sterilization requirements, it can be safely assumed that the temperature in the chamber where the load is located will be higher. The drain is often covered by a removable mesh filter which traps debris, keeping the rest of the drain line clear. Steam Trap In order to raise the pressure inside the sterilization chamber, once the air is removed, the chamber must be completely sealed so that it is air/pressure tight. A tight lock and gasket seals the door. The drain outlet is sealed with a steam trap. As air is being removed from the chamber, the trap remains open. Once all of the air has been removed from the chamber, and only pure steam is flowing down the drain line, the thermostatic trap closes it off. With the trap closed, steam continues to flow into the chamber. As the amount of steam in the chamber increases, the pressure increases. And as pressure increases so does the temperature. Pressure and temperature rise to a preset level and are then held for the required sterilization (exposure) time. At the end of the exposure time, the trap opens to allow steam to flow out and the pressure in the chamber to decrease. In some sterilizers, the trap is controlled by a heat (thermostatic) sensor. In others, an electric solenoid is used. Advantages of Steam Sterilization  Relatively fast compared to other sterilization methods  No toxic residuals on devices  No toxic by-products © Vancouver Community College 6 Medical Device Reprocessing Theory Modules Module 9: Sterilization  Good penetrating power through packaging to reach the internal device once all air is removed  Most reliable method compared to other sterilization methods Disadvantages of Steam Sterilization  It requires the complete absence of air  It is unsuitable for items that are anhydrous, heat-sensitive or made of wood or cork (**see notes below)  The sterilizer, loading rack, and rack carriage are hot after a cycle, and can cause burns ** Anhydrous materials are those without water. They do not mix with water and therefore do not mix with steam either. Examples of anhydrous materials are oils, grease and powders. ** Heat-sensitive items are items that cannot withstand high temperatures and may melt or be otherwise damaged. ** Wood and cork are not suitable for steam sterilization because of their cellular structure. The arrangement of their cells makes them microscopically very porous. The pores will allow microorganisms to penetrate deep into the core of the wood or cork item. Yet, this same cellular arrangement prevents steam from circulating freely to reach all microorganisms. Sterilization cannot occur because some microorganisms are protected from steam contact by the cellular structure of the wood or cork. Within any space, steam tends to spread out in layers. Because it is lighter than air, the layers occur at the top of the space. This phenomenon is very similar to the effect achieved when mixing oil and water. Oil is lighter and sits on top of the heavier water in the same way that steam sits on top of air. For steam to fill an entire space, all the air must be removed from the space. If air pockets remain, steam may not penetrate the pockets, and/or air may cool the temperature of the steam. Either way, sterilization may not occur. 3. Types of steam sterilizers One way to differentiate types of steam sterilizers is through the method by which air is removed from the chamber at the beginning of a cycle. Air removal methods can be:  Gravity displacement (passive)  Dynamic (active) Gravity Displacement Air Removal The first, and once very common method of air removal, is that of gravity (or downward) displacement. This type of sterilizer was used in MDRD’s throughout the country before the dynamic air removal systems were developed. It is still used in many small, tabletop steam sterilizers. It operates without any mechanical assistance for air removal. Air removal is passive, and relies on temperature differences and the heavier weight of cooler air compared to steam for air to fall to the bottom of the chamber and flow out of it. Air trapping is a real risk. © Vancouver Community College 7 Medical Device Reprocessing Theory Modules Module 9: Sterilization As steam enters the chamber at the beginning of a cycle, it collects at the top. The cooler, heavier air sinks to the bottom. As more and more steam fills the chamber from the top down, air is pushed down and out through the drain line. Air removal is a relatively slow process by the gravity displacement method. A gravity displacement sterilizer often operates at a temperature of 121o C (250o F). Exposure time can be as long as 20 – 50 minutes depending on the items being sterilized and the temperature used. There are two disadvantages to gravity displacement. First, it is slow, because the layering tendencies of steam and air result in slow air removal. And second, air can be trapped in pockets. For example, if a bowl or basin is left upright, air cannot drain away and will continue to sit in it. Because it is cooler and heavier than steam, the air will fall to the lowest point of whatever contains it (Image 9.4). If air remains, steam at the appropriate temperature will not contact the protected surface, and sterilization will not occur. That is why it is important to place all items that might trap water or air on their sides, and tilted forward. Air and steam can then flow freely and nothing is trapped. Image 9.4: Correct positioning of cupped (concave) surfaces (VCC) Sterilizing Liquids Some sterilizers have a special cycle that will sterilize liquids, although in today’s MDRD’s this is rarely done. The Liquids Cycle uses the gravity air removal method. The key difference between a liquids cycle and the standard gravity cycle is that the liquids cycle uses a slow exhaust at the end of the cycle. Rather than quickly removing the steam and rapidly altering the pressure, the chamber is slowly returned to normal atmospheric pressure and temperature. If this were not done, rapid changes in temperature could break the glass flasks containing the liquids. The slow exhaust lengthens the cycle considerably. A common sterilizing temperature for a liquids cycle is 121°C. The sterilizing (exposure) time will vary with the volume of the solution to be sterilized. For example:  75 to 250 ml – 20 min exposure  500 to 1000 ml – 30 min exposure  1500 to 2000 ml – 45 min exposure Dynamic air removal Because of the length of time involved in gravity displacement sterilization, larger steam sterilizers use a “dynamic air removal system” to rid the chamber of air at the start of a cycle. Dynamic systems use active means to remove air from the chamber. There are two (2) different systems that will actively remove air from the chamber:  Prevacuum  Steam-flush/pressure pulse (SFPP) © Vancouver Community College 8 Medical Device Reprocessing Theory Modules Module 9: Sterilization Both systems create turbulence in the loaded chamber by injecting short pulses of steam at the beginning of a cycle. This turbulence disturbs air pockets and allows air to be removed from the chamber more rapidly than by the Gravity Displacement method. Prevacuum air removal Just as the name says, in this type of a system, a vacuum pump, situated in the drain line mechanically removes air from the chamber before the actual sterilization (exposure) phase begins. A short pulse of steam is injected into the chamber and then the air and steam mixture is sucked out of the chamber by the vacuum pump. A negative chamber pressure is created. As steam is injected into the chamber again, the pressure in the chamber increases from negative to positive. This injection—removal combination is repeated 3 or 4 times, each time creating turbulence in the chamber. The turbulence releases air pockets that may be trapped in the chamber or in packages within the load, allowing the air to be pulled into the drain by the vacuum pump. Compared to Gravity Displacement, air removal by the Prevacuum method is very quick. Once all air has been removed, steam continues to flow into the chamber, raising the pressure and consequently the temperature of the steam. When the preset sterilization temperature is reached, timing of the sterilization exposure can begin. For steam sterilizers manufactured by the Steris Corporation (e.g. the Amsco Evolution series), common sterilizing parameters for a Prevac sterilizer cycle for wrapped packages are 132°C for 4 minutes. For sterilizers manufactured by the Getinge Group, common parameters for wrapped packages are 134°C for 4 minutes. It is important to know the parameters for the make and model of the sterilizer that you will be operating in a MDRD and follow the sterilizer manufacturer’s explicit instructions regarding the standard sterilization time and temperature to be used. At the end of the cycle, the vacuum pump removes steam from the chamber and assists with drying of the load. Steam-flush-pressure-pulse air removal In a sterilizer that uses steam-flush-pressure-pulse (SFPP) for air removal, pulses of steam are injected into the chamber and turbulence is created, similar to that in a Prevac sterilizer. However, rather than drawing a vacuum (negative pressure) to remove the air-steam mix, an electronic solenoid valve opens to allow the mixture to escape. The electronic solenoid optimizes the expulsion of trapped air. Pressure in the chamber never falls below 0 psig i.e. there is always a positive pressure in the chamber. Depending on the sterilizer model and type of cycle, the SFPP is repeated 2 or 3 times. Each time, the turbulence disturbs trapped air, allowing it to flow out of the chamber. Similar to the Prevac method, once all the air is removed, steam will continue to flow into the chamber, raising the pressure and consequently the temperature of the steam. When the preset sterilization temperature is reached, timing of the sterilization exposure begins. Common sterilizing parameters for a SFPP wrapped cycle are 132°C for 4 minutes. And as with Prevac sterilizers, manufacturer determined parameters vary, so MDRD’s must follow the instructions for the specific sterilizer that is being used. The key difference between Prevac and SFPP sterilizers is that while the Prevac requires a vacuum pump to remove air and operates under negative pressure (vacuum) during part of the cycle, the SFPP cycle is © Vancouver Community College 9 Medical Device Reprocessing Theory Modules Module 9: Sterilization always under positive pressure. This eliminates the potential for air to leak into the chamber during times of negative pressure during the conditioning phase, which could occur through a leak in piping or through a damaged door gasket for example. Reducing the possibility of air in the chamber, makes it more likely that conditions for sterilization will be achieved. Phases of a Prevac Air Removal Sterilizing Cycle In general, a dynamic air removal sterilization cycle has three phases. These are the standard phases of a Prevac cycle:  Condition  Sterilize (exposure)  Exhaust Phase I - Condition During conditioning, steam is injected and air is removed in pulses. The steam-air pulsing continues until all air is removed from the chamber. At that point, the pressure increases until the preset temperature of 132o C is reached. The graph below (Image 9.5) shows a visual representation of a Steris/Amsco Prevac sterilizer cycle1 The 4 conditioning pulses are circled. Notice that as the vacuum pump removes the air-steam mix from the chamber, the pulses dip below 0 PSIG. Each time this happens there is a vacuum (negative pressure) in the chamber. Image 9.5: Conditioning phase Amsco Century Medium Steam Sterilizer. Operator Manual 12/16/05 Section 5.17 © Vancouver Community College 10 Medical Device Reprocessing Theory Modules Module 9: Sterilization Phase II - Sterilize The actual sterilizing period is called the exposure time. Common exposure temperatures and times are:  132o C for 4 minutes  134o C for 4 minutes  135o C for 3 minutes The image 9.6 below shows a visual representation of a Steris/Amsco Prevac sterilizer cycle (Steris, 2012, p. 5.17), with the Sterilizing phase circled. Image 9.6: Sterilizing phase The sterilizing (exposure) time has three (3) parts: 1. Heat-up Heat-up occurs once all air is removed and steam has spread through the entire chamber. The chamber has reached a temperature of 132o C but the core of items to be sterilized has not. This phase allows core temperatures to heat up to 132o C and takes about one minute. 2. Hold Once a core temperature of 132o C has been achieved, the load is held at this temperature for two minutes. Research has shown that two minutes at 132o C will kill even the most resistant microorganisms. Less resistant ones will die much more quickly, but the sterilization process is designed to destroy even the most resistant microorganisms. 3. Safety To ensure that microorganism death has been achieved, a safety margin is added to the time. The load is held at 132o C for an additional one minute. This brings the total exposure time at 132o C to 4 minutes. © Vancouver Community College 11 Medical Device Reprocessing Theory Modules Module 9: Sterilization Phase III - Exhaust After sterilization conditions have been achieved, steam is removed from the chamber through the drain. This is called the exhaust phase. The vacuum pump pulls out the steam and creates a negative pressure within the chamber. This helps to pull moisture from the packages. Then heated, filtered fresh air flows into the chamber. This air, along with the heat of the chamber and the hot items in the load, vaporizes residual water and removes it from the load and chamber. The load is dried. Drying time is preset by the sterilizer operator, and can vary (e.g. 15-55 minutes) depending on the load. Once drying is complete, the chamber is returned to normal atmospheric pressure. At this point, the operator will verify the sterilization parameters on the printout. (Printout verification is addressed in more detail later in this module.) After the conditions are verified, the door is opened, and the load removed. 4. Managing a steam sterilization cycle This section on managing a steam sterilization cycle includes; loading the sterilizer, selecting a cycle, monitoring the cycle as it progresses, and unloading the sterilizer once the cycle is complete. It also includes information about routine sterilizer maintenance. Loading Steam sterilizes by direct contact i.e. it can only sterilize the parts of devices that it can physically touch. To ensure direct contact, steam must be able to circulate freely in the chamber and penetrate all packaging materials to reach the devices that need to be sterilized. To achieve this, the sterilizer chamber must be loaded correctly. Image 9.7: Loading a steam sterilizer (K Scott) The following are guidelines for loading a sterilizer.  Check that the packaging is appropriate e.g. wrapper type, package size and package density. Poor sterilant penetration and wet packs can result from improper packaging.  Ensure that placement of packages on the loading carriage will allow for free circulation of the sterilant around all packages and penetration into each pack. o Packages must not be crowded together. Allow at least 2" to 4" (5 cm to 10 cm) between large packages such as large basin sets. Allow 1" to 2" (2.5 cm to 5 cm) for smaller items such as single bowls, jugs and peel-back pouches. © Vancouver Community College 12 Medical Device Reprocessing Theory Modules Module 9: Sterilization  Do not stack packages directly on top of one another. Each layer of packaging must be placed on a separate shelf. The only exceptions to this are rigid containers that have been specifically validated by the manufacturer for stacking. Not all containers have this validation so check the instructions for use.  Do not over load. It is much safer to do two small loads than one large load.  Items to be sterilized should be positioned on edge. This allows air to be removed easily and minimizes resistance to the free circulation of the sterilant, ensuring its contact with all surfaces. Large linen bundles, mayo trays and basins are examples of such items. Instrument sets in trays and boxes that have perforated tops and bottoms and are wrapped should remain flat so that the sterilant can flow through the perforations. Rigid containers with solid bottoms may be placed flat for a dynamic air removal sterilization cycle.  Position peel-back pouches on edge with the plastic side tilted slightly forward. Face the paper side of one pouch to the plastic side of the next. This ensures penetration by the sterilant and prevents condensation between the two plastic (waterproof) surfaces. Image 9.8: Peel-back pouches on sterilizer carriage (K Scott)  Items which may trap water such as bowls, basins, trays, and peel-back pouches must be placed on edge and tilted forward (Images 9.8 and 9.9). © Vancouver Community College 13 Medical Device Reprocessing Theory Modules Module 9: Sterilization Image 9.9: Tilted basins on sterilizer carriage (K Scott)  Load items within the confines of the loading rack to prevent packaging from touching the sterilizer chamber wall. Touch points could create condensation and lead to wet packs.  Whenever possible, sterilize similar items in the same load i.e. all instrument sets, all stainless steel basins, all wrapped items, and all linen bundles (Image 9.10). Image 9.10: All wrapped load (K Scott) © Vancouver Community College 14 Medical Device Reprocessing Theory Modules Module 9: Sterilization  If loads must be mixed e.g. linen bundles and hard goods such as stainless steel or instruments in rigid containers, place hard goods on the lower shelves (Image 9.11). This prevents linen packages and wrapped items from becoming wet by condensation from stainless steel items or instrument containers. Image 9.11: Mixed load with wrapped items on top and rigid containers on bottom (K Scott)  Tabletop sterilizers have a mesh or perforated grid in the bottom of the chamber. The grid is removable for cleaning but must be in place during sterilization. It allows sterilant to circulate through the chamber. (Images 9.12 a, b) Image 9.12a: Tabletop sterilizer with perforated grid Image 9.12b: Tabletop sterilizer without perforated grid (K Scott) © Vancouver Community College 15 Medical Device Reprocessing Theory Modules Module 9: Sterilization Selecting a Cycle Before running a cycle, sterilization (exposure) temperature and time as well as drying time can be selected via controls found on the front of the sterilizer. The control panels of each make and model of steam sterilizer will be somewhat different. (Images 9.13 and 9.14) on the next page illustrate various models of sterilizers. Getinge and Steris (Amsco) are major suppliers of steam sterilizers to Canadian MDRD’s. To illustrate some of the following information, images of sterilizers from each of the companies are used, but be aware that these are not the only manufacturers, nor are the models shown the only ones that are in use. Controls Each sterilizer will have a means for the operator to control the:  Power to the unit (on-off switch)  Door opening and closing  The type of cycle that will be run i.e. preset sterilizing exposure temperature and time plus drying time(cycle selector)  A means to manually cancel a cycle in progress if necessary Many controls are touch pads or touch screen panels. Control panel Image 9.13: Getinge sterilizer Image 9.14: Steris (Amsco) sterilizer Getinge 400HC-E and 500HC-E Series Product Specification. Steris Amsco 400 series medium HC_ST_400-500HCE_04131_EN_US©2013 (http://www.steris.com/products/steam-sterilizer/amsco- 400-series-medium-steam-sterilizer) © Vancouver Community College 16 Medical Device Reprocessing Theory Modules Module 9: Sterilization Displays Associated with the controls will be displays. Displays provide information about what is happening in the sterilizer at the moment (i.e. as the display is being viewed). It will provide the operator with real- time information about the cycle in progress, including:  The type of cycle that was selected  The sterilizing time and temperature of the cycle that was selected  Current temperature in the chamber  Amount of time remaining in the cycle i.e. until drying is completed Images 9.15 and 9.16 below show some typical cycle status displays. Image 9.15: Amsco Century Steam Sterilizer Image 9.16: Getinge 400/500 HC-E Steam Sterilizer © Vancouver Community College 17 Medical Device Reprocessing Theory Modules Module 9: Sterilization Pressure gauges On the front of many sterilizers, there may also be two gauges. One indicates pressure in the jacket; the other indicates pressure in the chamber. (Image 9.17) Jacket pressure When the sterilizer power is turned on and there is steam in the jacket, whether a cycle is in progress or not, at 132o C jacket pressure will be close to 27 psig or 42 psia. Chamber pressure When no cycle is operating and the chamber is empty, chamber pressure will be 0 psig (or 15 psia). During a cycle, chamber pressure will fluctuate during the conditioning phase as pulses of steam and air move in and out of the chamber. During the exposure time, the pressure will remain steady at about 27 psig (or 42 psia). Jacket and Chamber Pressure Gauges Steris/Amsco Steam sterilizer Image 9.17: Pressure gauges Getinge Steam sterilizer © Vancouver Community College 18 Medical Device Reprocessing Theory Modules Module 9: Sterilization Recording Device This device automatically prints a cycle record of the cycle phases and sterilizing time and temperature during each cycle. It is usually a computer print-out, sometimes called a tape. Newer models can also provide an electronic record of sterilizing conditions which can either be downloaded onto a USB stick or directly into the MDRD’s computer system. The conditions recorded on the cycle record are what the MDRT must check at the end of each cycle before removing the load from the sterilizer. These records are legal documents and must be retained. Verifying sterilization conditions is covered later in this module. (Image 9.18) Printout Steris/Amsco Steam sterilizer Image 9.18: Sterilizer printouts Getinge Steam sterilizer Choosing and Operating a Cycle The information presented in this module so far provides preparation for on- the- job training in how to choose and operate a cycle. In general, these steps should be followed:  Determine the type of cycle that you will be running (e.g. Wrapped)  Complete the labeling of each package that will be in the load i.e. add a load control label identifying the date of sterilization, the sterilizer number and the cycle number in that sterilizer. Image: 9.19 Load control label (K Scott) © Vancouver Community College 19 Medical Device Reprocessing Theory Modules Module 9: Sterilization  Load the chamber with only those packages that are compatible with the cycle. Follow the loading principles described on pages 182 and 183 of this module.  Record all of the items that are in the load.  Use the touch pad on the control panel, or the locking mechanism on the door to close and lock the door.  Use the touch pad to choose the desired cycle. Read the panel to confirm that it will provide the conditions (sterilizing temperature and time as well as dry time) required.  Press the “Start” pad to begin the cycle. Unloading the sterilizer When the sterilization cycle is complete, three things will happen:  An audible alarm (buzzer) will sound  The display screen will show the words “Cycle Complete” or something similar  A permanent record e.g. printout of the conditions in the chamber during the cycle will be created Before removing the load from the sterilizer, check the cycle record e.g. printout, and verify that the conditions for sterilization were achieved in the cycle just completed. The specific requirements for cycle verification are discussed later in this module. The sterilizer loading rack will be hot when removing the load, so protection from thermal burns by the use of clean oven mitts or the specially designed handle to grab the cart and pull it out of the chamber is required (Image 9.20). Image 9.20: Unloading the sterilizer (K Scott) © Vancouver Community College 20 Medical Device Reprocessing Theory Modules Module 9: Sterilization After the sterilization cycle is complete and the parameters have been checked, the load can be removed from the chamber. Before the packages can be stored, however, they must be completely cool i.e. at room temperature. During this time, the packages should remain on the sterilizing carts and be moved to a designated cooling area near the sterilizers. This area should be out of the main traffic flow, and away from heating or cooling vents and air-conditioning. Depending on the size and types of packages, they may need to cool for 30 – 60 minutes until they have reached room temperature. The image below shows a warm load cooling directly below an air conditioning vent. This is incorrect. Image 9.21: Incorrect cooling under an air vent (K Scott) Sterilized packages that are still warm should not be touched or handled. Warm items should not be transferred by hand from the cart to cold metal racks or shelves for cooling. The contrasting temperatures could cause condensation which in turn could “wick” microorganisms from the outside of packages through to the inside, thereby contaminating the devices. For some packages and some departments, a portion of this cool-down period may take place with the load remaining in the sterilizer chamber with the door ajar. Follow the written work instructions provided by the MDRD. Once the load has been removed from the chamber, close the sterilizer door to maintain the stand-by temperature in the chamber. Once the load has cooled, and packages are being unloaded from the sterilizing racks or carts, it is important that each package is checked for:  Correct change to the chemical indicator. Detailed information about chemical indicators will be found in the next section (Quality Assurance) of this module.  Unbroken seals  Integrity—no holes, tears or other damage to packaging materials  Dryness—wet packages are considered to be contaminated  Cleanliness, i.e. no contaminants (e.g. visible staining or soil) © Vancouver Community College 21 Medical Device Reprocessing Theory Modules Module 9: Sterilization Any package that does not meet acceptance criteria must be repackaged and re-sterilized. The chemical indicators must be replaced. Wet Packs Occasionally, packages or instrument sets will be wet following the sterilization cycle. Because wet packages are considered to be contaminated and cannot be used for patient care, necessary measures must be taken to prevent wet packs from occurring. Wetness may be found on a package in the form of dampness, droplets of water on or in the package, or a dried watermark on the wrapper. The package must be considered unsterile because the moisture on or within the package has the potential to create a path for microorganisms to move from the outside to the inside of a package. When a wet pack is found, all other packs processed in the same sterilizer load must be carefully checked. Check the printout to see that correct parameters were used (correct cycle) and sterilizer is operating correctly. The reason for the wet pack must be identified and steps taken to correct the problem. Causes of wet packs include: Improper loading of the sterilizer  Items packed too tightly, closely touching one another  Items touching chamber walls  Incorrect positioning: o Not on edge o Upright cupped surfaces trap water  In mixed loads, stainless steel goods loaded on shelves above soft goods Improper packaging  Water-resistant wrappers can retain moisture, especially if wrappers have excessive layers or folds.  Items wrapped too tightly  Items too heavy or improperly arranged within the package Plugged drain line  Steam cannot exhaust properly Items wet prior to sterilization  Sterilizer will remove only the amount of steam it introduces. Excess moisture will remain on items at the end of the cycle. Dirty chamber  Chemical and mineral build up on walls can act as condensation points – water will drip onto packages Wet steam  Steam that is formed by gently boiling water is called saturated or dry steam. This steam is a vapour and does not contain water droplets in any great amounts. This is the type of steam necessary for proper sterilization. © Vancouver Community College 22 Medical Device Reprocessing Theory Modules Module 9: Sterilization Sometimes, though, water will boil very violently. Besides releasing water vapour, violent boiling also throws off larger water droplets as the bubbles burst on the surface of the water. If steam is made up of more than three percent of these water droplets along with the water vapour, it is known as wet steam. The water droplets of wet steam tend to soak the packs with which they come in contact and the sterilizer drying phase is unable to completely dry them. Storage while hot  If the packages were placed on metal storage shelving while still warm or damp, the temperature differences between the shelving and packaging could cause condensation. Extended Cycle Recently many manufacturers have validated their medical devices to be sterilized in extended cycles. For example, rather than 4 minutes exposure time they recommend 5 minutes, 8 minutes, 10 minutes etc. Make sure manufacturer’s instructions are followed when sterilizing medical devices. Most sterilizers will have a control panel where the cycle can be changed if necessary. Immediate Use Steam Sterilization (IUSS) Flash Sterilization IUSS by definition is the “emergency steam sterilization of a medical device by the unwrapped method.” It is designed for the unplanned or emergency reprocessing of individual medical device in an operating room setting when time is insufficient for use of the preferred wrapped or containerized sterilization methods. IUSS should only be used if:  A unique instrument has been contaminated and needs to be replaced to the surgical field immediately  An instrument has been dropped on the floor and is needed to continue a surgical procedure  Specific instruments are needed for an emergency surgical procedure  There is no other sterilization alternative IUSS sterilization shall not be used to sterilize implants, nor should it be used to sterilize complete sets or trays of instruments. The IUSS cycle is generally a much faster steam sterilization method than the usual Gravity Displacement and Prevac cycles because:  The device is not wrapped. Steam does not have to permeate through packaging material to be in contact with all surface of the device to be sterilized  Unwrapped device placed on an open tray minimizes trapped air in the chamber  Sterilizer chamber size is usually small, just enough to accommodate a tray which holds one or two devices  No drying time is required. However, some facilities do use a minimal drying time to remove excessive moisture  Some IUSS sterilizers have a cycle for single wrapped devices. An IUSS sterilizer cycle designed to permit instrument trays to be wrapped with a single wrapper (nonwoven or woven textile) is available on some dynamic air removal-type steam sterilizers. The single wrapper serves only to confine the sterilized items and protect them from environmental contaminants that might be encountered as they move from the sterilizer to the point of immediate use. If it is necessary to use a single wrapped tray, the sterilizer manufacturer’s guidelines for use shall be followed because this process is expected to yield a “wet package” © Vancouver Community College 23 Medical Device Reprocessing Theory Modules Module 9: Sterilization Handling and preparation of devices for Immediate Use Steam Sterilization The handling and preparation of devices for IUSS is the same as for routine sterilization: devices must go through decontamination and inspection. Personnel and environmental requirements do not differ from those used for routine sterilization. Transfer of IUSS devices to point-of-use Immediate use steam sterilized devices that are hot and wet can be contaminated by airborne particles during transportation. They can be easily contaminated by contact contaminants transferred from handling as well. The more metal mass of instrumentation in a tray, the more likely they will be wet after the flash sterilization process. The tray taken from the sterilizer, which is hot and wet, collects dust, debris, and microorganisms more readily than dry, cool trays with a barrier protection. It is difficult to deliver IUSS devices aseptically. Some manufactures have specifically validated containers that are used to protect sterile devices during transfer. Image 9.22: IUSS container (K Scott) Monitoring the immediate use steam sterilization cycle The cycle records (printout) as well as chemical and biological indicators designed specifically for the IUSS are used to monitor each cycle. Record keeping As the immediate use steam sterilization cycle presents more variables and risks than the routine steam sterilization cycle, vigorous record keeping is required. The current best practice guidelines recommend that record keeping for each load should include:  Date of the IUSS cycle  Name of person who decontaminated and prepared the device  Identification of sterilizer  Sterilizer load number  Type of sterilization cycle used  Load content  Sterilization exposure time and temperature  Time of cycle from start to completion © Vancouver Community College 24 Medical Device Reprocessing Theory Modules Module 9: Sterilization  Identification of sterilization cycle operator  Operating Room identification  Surgeon identification  Surgical procedure  Patient identification  Reasons for IUSS sterilization  Results of the cycle record and chemical, biological tests, as well as the Air-removal test if applicable 5. Routine maintenance of steam sterilizers Most sterilizer maintenance will be performed by qualified service technicians. Any maintenance activities performed by a service technician should be documented by the technician and a copy of the work performed should be retained in the MDRD. There are some maintenance tasks that are performed by the sterilizer operator and they will often include the following: As required, change the printer paper roll and the printer ink cartridge/ribbon Daily, clean the chamber drain strainer. o Remove the strainer from the drain o Remove obvious debris from the strainer. Use a brush, wire or similar tool if necessary o Reverse flush the strainer under running water. o Replace the strainer in the drain. Weekly, flush the chamber drain o Turn the steam supply off and cool the chamber to room temperature o Remove the drain strainer o Pour a solution of 15 ml Trisodium Phosphate (TSP) mixed with 500 ml of hot water into the drain. o Replace strainer in the drain As necessary, clean the chamber following spills or other soiling o Turn the steam supply off and cool the chamber to room temperature o Remove shelves or loading cart o Wash the inside of the chamber and the shelves with a mild detergent solution At all times, refer to the sterilizer operator’s guide for specific information about the routine maintenance requirements for the sterilizers used in the MDR department. © Vancouver Community College 25 Medical Device Reprocessing Theory Modules Module 9: Sterilization 6. Quality Assurance for Steam Sterilization Routine monitoring Routine monitoring of the sterilization process is an essential part of quality assurance. Ironically, the actual sterility of any processed item cannot be directly verified. The only way for that to be done would be to open the package, swab the sterilized device and culture it. Obviously, opening the package would destroy the sterility of the device and it could not be used on a patient. So, rather than monitor the device itself, sterilization monitoring focuses on the process of sterilization. The following three (3) types of monitoring indicators are routinely used monitor different parts of the process:  Physical indicators  Chemical indicators  Biological indicators Each type of indicator provides different information which, when put together, gives reasonable assurance that sterilization has occurred. However, it is important to remember that if a device is not correctly cleaned, packaged, and/or loaded into the sterilizer, sterilization could fail, no matter what any of the indicators say. Type of Indicator Information provided Physical (displays and gauges) Conditions in the sterilizer chamber at the sensor location (usually at the bottom, near the drain) Chemical Conditions in and around the packages Biological That the process will kill resistant microorganisms (spores) Physical indicators — display and cycle record Remember that cycle displays are located on the front of every sterilizer and provide information about what is happening in the sterilizer chamber at the moment (i.e. as the display is being viewed). However, a display does not necessarily indicate what is happening within the load itself. Nonetheless, it will provide the operator with real time information about the cycle and conditions in the chamber as the cycle progresses, including:  The type of cycle that was selected  The sterilizing time and temperature of the cycle that was selected  Current temperature in the chamber  Current pressure in the jacket and chamber (either on the display panel or via pressure gauges)  Amount of time remaining in the cycle i.e. until drying is completed At the end of the cycle, the information that was displayed on the panel is transferred to a permanent record. The record can be in the form of a printout or an electronic file. © Vancouver Community College 26 Medical Device Reprocessing Theory Modules Module 9: Sterilization The sterilizer operator, in addition to loading the sterilizer and selecting the correct cycle, is responsible for ensuring that conditions for sterilization (sterilizing exposure temperature and time) were met during each sterilization cycle, (e.g. 132o C for 4 min). This means that:  The control panel should be checked frequently during the cycle. Check the display to determine the stage of the sterilization process. Then check temperature and pressure to see that they are as expected for the phase that the cycle is in.  Before removing the load from the chamber, check the cycle record/printout to ensure that conditions for sterilization have been achieved. By checking the cycle record immediately, problems can be identified early, and patients can be protected from the infection risk posed by the release of unsterile goods. The sterilization cycle record (printout or electronic record) The sterilization record is an important, legal document. The Canadian Standards Association (CSA) requires that every sterilization cycle be documented and that the record be retained to show that conditions for sterilization were met. (Canadian Standards Association, 2014) The cycle record must show the following information:  Date and time of the sterilization cycle  ID of the sterilizer in which the load was run  Load/cycle number in the sterilizer on the day the cycle was run  Cycle parameters of sterilization i.e. time, temperature and pressure  Initials of sterilizer operator The sterilizer operator, by initialing the record, confirms that the correct conditions for sterilization were achieved. It is absolutely imperative that the record is checked closely before it is signed! It is a legal document, and as such, it must be kept in a safe place from which it can be easily retrieved. © Vancouver Community College 27 Medical Device Reprocessing Theory Modules Module 9: Sterilization Interpreting the printout Image 9.23 is a copy of a Prevac cycle printout from a Steris/Amsco steam sterilizer. The printout from each type of sterilizer will be a bit different, but the same type of information will be contained in each. In this example, read the tape from top to bottom. The time and date of the cycle are printed across the top. Here, the cycle start time was 52 min. after midnight on 02 Nov. 2010. The pre-selected settings are those that can be set by the operator when a cycle is chosen. Standard/preset settings are shown on the tape. For this cycle a sterilizing temperature of 134 °C for 4 min with a drying time of 30 min. was selected. There are four columns of data recorded for each cycle. The left most column lists letters indicating the cycle phase.  C = Conditioning  S = Sterilize  E = Exhaust  Z = Cycle Complete The second column notes the time at which the temperature and pressure were recorded. In this example, the cycle began at 52 min after midnight and ended at 1:42 AM The third column records the temperature. In this example the readings are in oC (T=C at the top of the column). Most sterilizers can be set to record in either oF or oC. In this cycle, the temperature ranged between 66.7 °C and 135.6°C. During Conditioning (Phase I), the temperature and pressure fluctuate when air is removed and steam is injected in pulses. During sterilization (Phase II) the temperature remains, above 134oC. Temperature drops during exhaust (Phase III) as steam is removed and filtered air is drawn into the chamber. The fourth column records pressure (p) and vacuum (v). As steam is injected, pressure rises. As air and/or steam are removed, pressure falls. In fact it falls so low that a vacuum (v) or negative pressure occurs in the chamber. As this column is read from top to bottom these changes are evident. Image 9.23: Prevac cycle printout (K Scott) © Vancouver Community College 28 Medical Device Reprocessing Theory Modules Module 9: Sterilization Verify the printout Once the cycle is complete, the sterilizing conditions in the cycle must be verified. Actual temperature and time (not the preset ones at the top of the tape) must be at or above the preset parameters. Check the Minimum Temperature The minimum temperature is highlighted in yellow at the bottom of the printout. It must be at or above the preset temperature (134°C in this example). The minimum temperature was 134.1°C so it is acceptable. Check the Sterilization time The sterilization time is highlighted in yellow at the bottom of the printout. It must be match or exceed the preset time of 4 min. In this example, the actual sterilization time matches the preset time of 4 min. The time is acceptable. Document your verification Either circle the actual sterilization time and temperature, or put a tick beside each to indicate that the readings have been checked. Once done, initial the printout. The printout is considered a legal document. Initialing the printout confirms that sterilizing conditions were achieved in this cycle. It is important to understand what is being signed. Leak Test Part of the quality assurance process for a Prevac steam sterilizer is to routinely test it to ensure that there is no air in the chamber during sterilization (exposure) phase. There are 2 tests that are performed on Prevac steam sterilizers to check for the presence of air; the vacuum leak test or vacuum leak rate, and the air removal (Bowie Dick) test. The Air Removal (Bowie Dick) test verifies that the vacuum pump in the sterilizer is working as it should and all air present in the chamber at the start of the cycle is drawn out of the chamber before the sterilization exposure phase begins. The Air Removal Test is further addressed later in this module. The Leak Test is used to monitor the sterilizer pressure vessel components between service calls. It checks the integrity of the sterilizer chamber and plumbing i.e. the pressure vessel, to verify that there are no leaks that could allow additional air to enter the chamber during a cycle. The Leak Test can help assess the functioning of various parts of the sterilizer pressure system and may give an early indication of wear and tear on component parts. New models of sterilizers have a Leak Test coursemed directly into their cycle selection panel. During a Leak Test cycle, a vacuum is drawn in the empty chamber, and the rate, at which the vacuum is lost over a period of time, usually 10-15 minutes, is measured. Each sterilizer manufacturer will specify acceptable parameters, but a common standard is a vacuum loss of no more than 1 mm Hg (Mercury) over 10 minutes. Each sterilizer manufacture will recommend the frequency at which the Leak Test should be performed, and it is typically daily or weekly. Document the results of each test. © Vancouver Community College 29 Medical Device Reprocessing Theory Modules Module 9: Sterilization When performing a Leak Test keep the following in mind:  It is only appropriate for Prevac cycles  A warm-up cycle should be performed before running a Leak Test. It is important that component parts of the sterilizer are at their operating temperature during the test.  The documented test result should be reviewed regularly by a knowledgeable person so that both trends and acute changes in rates can be identified and a service call initiated when necessary. Chemical Indicators (CIs) Chemical indicators are inks that respond to one or more sterilization parameters e.g. sterilization time, sterilization temperature, and/or steam quality, usually by a colour change. Chemical indicators are placed on both the outside (external) and the inside (internal) of each package before it is sterilized. The colour change of a chemical indicator shows that an item has been exposed to a sterilization process and that certain conditions were attained. This does not necessarily mean the item is sterile. For example, twenty indicators placed inside and outside a package could all change colour following a sterilization cycle. But the item itself may not be sterile if it was not cleaned properly or the wrapper is torn. Sterilization depends on proper preparation in addition to proper conditions. Therefore, chemical indicators give some assurance that sterilization conditions have been reached on the outside and inside of each package, but no conclusive proof that items are sterile. While chemical indicators do not verify sterility, they do allow the detection of potential sterilization failures due to factors such as incorrect packaging, incorrect loading of the sterilizer or equipment malfunction. Chemical indicators are designed to react to a particular type of sterilant. This means that different types of indicators must be used for steam, hydrogen peroxide vapour and ethylene oxide gas sterilization methods. They are not interchangeable. © Vancouver Community College 30 Medical Device Reprocessing Theory Modules Module 9: Sterilization There are six (6) classes of chemical indicators. The class number (class 1, class 2 etc.) reflects the type(s) of parameters that the CI will measure and the accuracy (sensitivity) of the measurement. The classes have no hierarchical significance i.e. 6 is not better than 4. Each provides different information which is summarized in the table on the next page. The CI manufacturer’s instructions for use must be read in order to determine the class. Class Description Process Indicators--demonstrates exposure to the sterilization process. Class 1 indicators will change colour in response to heat. Their pass/ fail window is large. The 1 colour change allows users to differentiate between processed and unprocessed packages. Sterilizer tape and indicator labels are examples of Class 1 indicators Specific Test Indicators , are designed to measure a specific attribute/condition e.g. 2 Bowie-Dick air removal test Single Variable Indicators respond (change colour) to a single sterilization variable (e.g. temperature OR time). They provide limited information regarding the overall effectiveness of the sterilization process. Their pass / fail window may be relatively 3 large. This means that they may begin to change at a time or temperature slightly below (or above) the standard parameters. They often take the form of a strip that can be placed inside a package before sterilization. Multi Variable Indicators respond to 2 or more sterilization variables (e.g. temperature AND time). Their pass / fail window will be narrower than that of a Class 4 3. As with the Class 3 indicators, most often they are a strip that can be placed inside a package. Integrating Indicators are designed to react to all the critical sterilization variables. In addition they have been tested against biological indicators (BI’s) and will only change 5 colour / appearance under the same conditions that would kill the spores in a B.I They are placed inside packages Emulating Indicators will react to all of the critical variables for one specific cycle. They will only change colour / appearance in response to very specific conditions i.e. 6 they have a very narrow pass/fail window. They are often used to monitor cycles with non-standard parameters e.g. 134°C for 10 min. They are placed inside packages. (Canadian Standards Association, 2014, p. Appendix B) The choice of chemical indicator will depend on the type and quality of information individual MDRD’s require. The responsibilities of the user related to chemical indicators are to:  Ensure that every package prepared has both an external and an internal chemical indicator on and in it. © Vancouver Community College 31 Medical Device Reprocessing Theory Modules Module 9: Sterilization  Know the expected colour change of the indicator following sterilization. All CIs are not the same colour either before or after sterilization. Before and after colours vary with the indicator manufacturer and the type of sterilant that is being monitored.  Check the chemical indicator for colour change every time a package is handled (e.g. when unloading the sterilizer, when putting packages away, when picking packages for distribution). External chemical Indicators External indicators are those that are placed on the outside of packages. They confirm that the outside of the package was exposed to the sterilant, but don’t provide any information about what happened inside the package. Every package that is sterilized must have an external chemical indicator. The tape that is used to seal wrapped packages, sometimes called indicator tape, is an external chemical indicator and must be on the outside of all wrapped packages no matter what sterilization process the item is going through. There are different types of external tape for the various types of sterilization (Image 9.24). Image 9.24: Various external sterilization tapes (K Scott) © Vancouver Community College 32 Medical Device Reprocessing Theory Modules Module 9: Sterilization Peel- pouches usually have a chemical indicator manufactured into the paper side of the package. (Image 9.25) shows examples of external indicators on pouches. Image 9.25: Peel-pouches unprocessed and processed (K Scott) And rigid container tags will often contain an external chemical indicator to show that the container has been exposed to the sterilant (Image 9.26). Image 9.26: Rigid container tags unprocessed and processed (K Scott) © Vancouver Community College 33 Medical Device Reprocessing Theory Modules Module 9: Sterilization Internal Chemical Indicators An internal indicator is one which is placed inside a package prior to wrapping. Being enclosed within the package, it gives information about what actually happened to the item being sterilized. It tells what types of conditions were achieved inside the package, not just on the outside of the package. Internal indicators can be paper strips, cards or tape. (Image 9.27) Image 9.27: Various internal chemical indicators Air Removal (Bowie-Dick) Test All air must be removed from the chamber before sterilization begins. Prevac sterilizers rely on a vacuum pump to remove the air. In order to confirm that there are no air leaks in the system and that the vacuum pump is working well and has removed the air as it should have during the conditioning phase, an air removal test is performed daily. A very common type of air removal test for Prevac sterilizers is the Bowie Dick. Note: An air removal test is not used in either a Gravity or Steam Flush Pressure Pulse type sterilizer. Check the SFPP sterilizer manufacturer’s instructions for use to see if there are other specific tests that must be performed to check for the presence of air. The Bowie-Dick test should be performed once each day, first thing in the morning, in an empty sterilizer before any other sterilization cycles are run. © Vancouver Community College 34 Medical Device Reprocessing Theory Modules Module 9: Sterilization A Class 2 chemical indicator test sheet used for the Bowie Dick is placed inside a process challenge device (PCD). A PCD is a pack that is designed to challenge or resist the ability of the sterilant (steam) to penetrate it and reach the test indicator within the PCD. Most Bowie Dick PCD’s are commercially prepared. There are many different types as you can see from the examples below (Image 9.28). Image 9.28: Various Bowie dick PCD’s (K Bhinder, K Scott) Departments can also make their own air removal PCD’s. Instructions for their assembly are described in Annex E of the CSA steam sterilization standard. When performing the test, you must follow the PCD manufacturer’s instructions for use. Usually the test is performed first thing in the morning. The PCD is placed horizontally at the bottom of an empty chamber, just above the drain (Image 9.29). © Vancouver Community College 35 Medical Device Reprocessing Theory Modules Module 9: Sterilization Image 9.29: Placement of a Bowie dick test pack (K Scott) Timing the cycle for this test is very important. It must be sterilized at 132 or 134o C for 4 minutes exactly (follow manufacturer’s instructions). The test cycle will not have a drying phase and the indicator must be read as soon as the cycle is completed. If the pack sits in the sterilizer at the end of the cycle for a longer period, or if more time passes while the pack is drying, the ink could continue to change colour and the test results could be incorrect. To read the test, remove the test paper from the pack. Examine the paper for even colour change across its entire surface. If a bubble of residual air remained trapped during sterilization, an area on the test sheet underneath the bubble will be lighter because steam will not have reached the heat sensitive indicator. If the test sheet is evenly coloured, it can be assumed that all air was removed. A uniform colour change is the key to this test, not the intensity of the colour change (Image 9.30 below). Image 9.30: Bowie dick tests, pass and failed © Vancouver Community College 36 Medical Device Reprocessing Theory Modules Module 9: Sterilization Keep in mind that the Bowie-Dick tests for air removal only. It does not test for the sterilizing time or temperature. Other indicators such as the printout are used to verify those variables. Biological Indicators (BI’s) Chemical indicators inform when an item has been processed and that conditions for sterilization have been achieved. But have all of the microorganisms been killed? Biological indicators (BI’s) are used to provide confirmation that conditions during a sterilizing cycle were sufficient to kill microorganisms. A biological indicator (Image 9.31) is a testing device made up of known quantity of non-pathogenic spores and a glass ampoule of growth medium, both contained within a plastic vial. The number of spores and resistance to the sterilization process far exceed those of the micro-organisms expected to be present on the items being sterilized. The non-pathogenic spore used to test steam sterilizers is called Geobacillus Stearothermophilus. Image 9.31: Biological indicator (K Scott) A BI is placed within a process challenge device (PCD) and processed through a sterilizing cycle along with other packages intended for patient use. At the end of a cycle, the BI is removed from the PCD and incubated. During incubation, the spores are provided with food, moisture and warmth, all of which support their growth. If any spores have survived sterilization, they will grow and the BI will change colour. If all spores have been killed, there will be no colour change. If no spores grow, it is assumed that conditions for sterilization were achieved. There are many types of BI PCD’s on the market. A MDRD will purchase and use the type of BI PCD that has been validated for use in a specific sterilizer and in the types of cycle(s) that are intended to be run. The BI test protocol is very precise and it may vary between BI manufacturers. The steps for the test and incubation of the BI will be described in each BI manufacturer’s instructions for use and must be followed exactly. © Vancouver Community College 37 Medical Device Reprocessing Theory Modules Module 9: Sterilization Performing a BI test Biological monitoring using a PCD should be performed every day that the sterilizer is used, in the first full load of the day. A BI PCD should also be included in any load containing implants e.g. orthopedic plates or screws. It should be performed in each type of cycle that will be run that day. For example, if a sterilizer has different cycles for wrapped instrument sets and linen bundles (and the time and temperature settings are different), both cycles must be tested. Or if a sterilizer can run both Prevac and Gravity cycles and you will be using both during the day, both cycles must be tested. The chamber should be fully loaded during the test. The BI PCD should be placed on the lower shelf, near the drain of the sterilizer. (Image 9.32) This is usually the coolest, and consequently the most challenging area of the chamber. Image 9.32: Placement of a BI PCD (K Scott) © Vancouver Community College 38 Medical Device Reprocessing Theory Modules Module 9: Sterilization Incubating a BI After the sterilizing cycle is complete, the BI must be incubated. At all times, follow the BI manufacturer’s instructions for use regarding preparation and incubation of the BI. In general, the steps will be as follows:  Allow the PCD to cool in the sterilizer (about 5 min.)  Remove the BI from the PCD and allow it to cool further (about 10 min.) o Some BI manufacturers recommend that Lot number gloves and safety glasses are worn when handling a processed BI. This is for user safety and is not related to handling biohazardous devices. BI’s are not biohazardous.  Verify that the CI on the BI capsule has changed to the correct colour  Confirm that the BI lot number (Image 9.33) matches the “Control” lot number. “Controls” are discussed Image 9.33: BI vial (K Scott) later in this module  Label the vial with the date and time at which incubation begins  Close the cap (if required) by pushing down on it  Crush the vial, which will then crush the glass ampoule. Crushing the glass ampoule releases a nutrient broth that bathes the spores contained in the vial. (Image 9.34) o Use the crusher provided by the BI manufacturer. It may be a manual device, or it may be built into the incubator  Do not crush the vial with bare hands. Glass from the ampoule inside the vial could pierce the plastic and cause injury. Image 9.34: Crushing the BI vial (K Scott) Place the vial in the incubator. Verify that the incubator is operating at the correct temperature (usually 55-60°C) (Images 9.35-9.37). Image 9.35: Steris incubator (K Scott) © Vancouver Community College 39 Medical Device Reprocessing Theory Modules Module 9: Sterilization Image 9.36: 3M rapid readout incubator (K Scott) Image 9.37: 3M super rapid readout incubator (K Scott)  Incubate the BI for the required time. Incubating the vial provides warmth to the moist, nutrient rich environment, all of which encourages any spores that might have survived sterilization to grow. o The incubation period varies with the BI design and manufacturer. It could be anywhere from 30 min. to 49 hrs. Follow the manufacturer’s instructions for use.  At the end of the incubation period, check the BI for colour change. Some incubators have sensors in them that will automatically check the colour change and notify the user when the incubation period is complete, and if the BI is positive or negative. Other incubators will require that the operator visually check for colour change. If all spores in the BI have been killed by the sterilization process, no spores will grow and there will be no colour change i.e. the BI will remain purple. The BI result is NEGATIVE. If spores in the BI have survived the sterilization process, and begin to grow, the BI will change colour, usually from purple to whitish or yellow. A colour change means that spore growth has occurred. The BI result is POSITIVE (Image 9.38). A positive BI indicates that the sterilization process may have failed. Information about what to do if an indicator shows a FAIL result is Positive BI Negative BI’s covered later in this module. Image 9.38: Positive and negative BI’s (B Bolding) For BI’s that has been processed through a sterilization cycle, the expected results are:  No spore growth  No colour change e.g. colour remains PURPLE  NEGATIVE If a processed BI changes to a whitish or yellow colour, or becomes cloudy, it is a POSITIVE result and could indicate a sterilization failure. It must be investigated. The results of the BI test are documented. © Vancouver Community College 40 Medical Device Reprocessing Theory Modules Module 9: Sterilization Using a BI “Control” When performing a BI test, always consider the possibility of a FALSE NEGATIVE result. A false negative can occur when a pre-existing problem with the BI prevents spores from growing. Problems could include things like:  No spores. Wrong spores. Dead spores. Glass ampoule not crushed.  Improper storage of the BI’s prior to use causes damage to spores and/or growth medium A “Control” minimizes the chance of a false negative test result and is an important part of a comprehensive quality assurance course. In a Control test, an unprocessed BI is crushed and incubated alongside a processed BI. The purpose of a Control is to demonstrate that if sterilizing conditions in the chamber did not occur, microorganisms (spores) would grow. With a Control test, after incubation, you expect the results to be POSITIVE. A Control test is usually run at least once per week and whenever a new box of BI’s is opened. The steps in a Control test are the same for a processed BI except that a BI that has not been sterilized is used.  Make a note of the BI lot number. It must match the actual test BI’s.  Label the capsule with: o The date and time at which incubation begins o “C” to indicate that it is the Control test BI  Follow the same steps for incubation used for a processed BI. Incubate the Control for the same time as the processed BI  At the end of the incubation period, check the Control for a colour change.  Because a Control BI that has not been processed through a sterilization cycle, the expected result is: o Spores have grown o The colour will have changed to yellow o POSITIVE Image 9.39: Control with a POSITIVE result (B Bolding) Documenting indicator and test results For quality assurance purposes, all sterilization test and indicator results must be documented. Complete cycle documentation includes:  A list of the types and quantities of packages that were sterilized in the load  A load control label, identical to those applied to the packages in the load  A printout or other type of permanent cycle record  Confirmation that a chemical indicator from the load changed to the appropriate colour  Results of any biological indicator tests associated with cycle Complete documentation is important for two reasons. First, it ensures that if there was a sterilization failure, packages from suspect loads could be retrieved / recalled. And second, it demonstrates that all © Vancouver Community College 41 Medical Device Reprocessing Theory Modules Module 9: Sterilization steps in the sterilization process were completed correctly and all test results were within acceptable limits, thereby assuring patient safety. The cycle documentation must be retained according to the MDRD’s policy and any relevant legislation. Often this is for seven years or more. Below is a sample of a form (record) used for cycle documentation (Image 9.40). Image 9.40: Sterilization control sheet (K Scott) © Vancouver Community College 42 Medical Device Reprocessing Theory Modules Module 9: Sterilization 7. Managing an adverse sterilization event The term “adverse sterilization event” most often brings to mind a failure shown by one of the monitoring indicators (printout, CI, BI). However, this is not the only adverse even that can occur. Problems with wet packs, package and device staining or spotting can also happen. Whatever the adverse event, the MDRD must have a plan to deal with it in an organized and comprehensive way. Failed monitoring indicators While a failed indicator may result from a true sterilizer failure, there are many other possible causes of an indicator failure and these must be investigated. At the same time, and until the investigation has been completed, the processed items associated with a failed indicator should not be used. And once the cause has been identified and corrected, any items from a failed cycle must be repackaged with fresh materials and re-sterilized. All chemical indicators must be replaced. Do not use any packages from a load with a failed indicator until the investigation is complete. And in all situations, when a failure occurs, notify your supervisor. The MDR department will have specific work instructions to guide staff through the management of an indicator failure. Those instructions must be followed. The following is a general outline of what to do should a sterilization monitoring indicator show a failure. The outline is based on guidelines from a number of sources including the Canadian Standards Association. If Printout indicates a failure  Check the remaining indicators i.e. chemical indicators, biological indicator. o If they indicate a failure, remove the sterilizer from service. o Do not use any packages from the failed load  If the CIs and BI pass: o Check for possible causes of time, temperature or pressure failure and correct any problems e.g.: air leak at door due to a damaged gasket or door not closed tightly. Correct the problem o Rewrap packages in the load, replacing all internal and external chemical indicators o Run the cycle again o If the second cycle passes, continue to use the sterilizer. If the second cycle fails, remove the sterilizer from service. If a Single Chemical Indicator indicates a failure  Check the remaining indicators i.e. printout, biological indicator and other CIs in the load. o If they indicate a failure, remove the sterilizer from service.  If the printout, BI and other chemical indicators in the load indicate a pass: o Check for and correct possible causes of failure e.g.  Overloading  Stacking © Vancouver Community College 43 Medical Device Reprocessing Theory Modules Module 9: Sterilization  Wrong cycle or settings selected  Wrong packaging material  Incorrect CI placement o Rewrap the affected package using new packaging material and replacing internal and external chemical indicators o Re-sterilize the package o The remaining packages in the load with the single CI failure may be used. If multiple Chemical Indicators show a failure  Check the remaining monitoring indicators i.e. printout and biological indicator. o If they indicate a failure, remove the sterilizer from service.  If the printout, and BI indicate a pass: o Check for and correct possible causes of failure e.g.  Overloading  Stacking  Wrong cycle or settings selected  Wrong packaging material o Rewrap the packages, replacing internal and external chemical indicators  Run the cycle again  If the CIs and printout of the second cycle pass, continue to use the sterilizer. If they do not, remove the sterilizer from service. If the Biological Indicator or Air Detection tests (Bowie Dick) show a failure  Hold (quarantine) all items in the load with the failed BI until the cause of the positive BI has been identified and corrected.  Do not use the sterilizer while investigating the failure  Investigate the possible causes of the failure and correct them. Human error is usually the most likely cause. Check the: o Other indicators i.e. printout and CIs  If these indicators also indicate failures, there is likely a problem with the sterilizer. Do not use the sterilizer or the collected items that were processed in it. o Position of the PCD in the sterilizer chamber e.g. pack location, overloaded chamber o Cycle selected (correct time and temperature)  Recall and quarantine (withhold from use) all items from the load in question and from every previous load from that sterilizer back to the load with the last negative biological indicator test.  Retest the sterilizer with a new BI PCD. Document the results. Hold all quarantined packages until the results of the BI re-test are known. o If the second BI test and the other indicators are negative, it is reasonable to assume that the failed BI was a false positive. The sterilizer may be put back into service and the quarantined packages released for use. o If the second BI is positive the sterilizer:  Must be serviced by a qualified technician © Vancouver Community College 44 Medical Device Reprocessing Theory Modules Module 9: Sterilization Must not be returned to service until it has been tested with 3 consecutive BI PCD’s, each in a fully loaded chamber. All results must be negative.  The non-PCD packages in the test loads must be kept out of use until the results of the all 3 BI tests are known. If they are negative, the test load packages may be used. They do not have to be repackaged and re-sterilized.  If the sterilizer is a Prevac, it must also be tested with 3 consecutive Bowie Dick air removal tests.  Any packages from positive loads, and all packages from the initial recall, must have their chemical indicators replaced and be rewrapped and re-sterilized before use. Documentation of monitoring indicator failure  Documentation of all failures and subsequent corrective actions should include: o Type of failure e.g. printout, CI, BI o Date and time of the questionable cycle o A description of the sterilizer and load with reference to the appropriate lot control number o Results of other load indicators o Contents of the failed package or load o Outcome of “recall” (if performed) o Activities undertaken to investigate o Results of any requalification testing performed Other Adverse events There are other indicators which provide early warning of a possible “Sterility Suspect” or “Sterilization Failure”, including:  Visible moisture on outside of packages  Visible moisture in the inside of the packages or in/on the devices  Packages that feel moist to the touch after the appropriate cooling period  Unidentified stains and spots on the outside of the packages  Unidentified stains and spots on the inside of the packaging material or on the devices  Debris on the inside of the packaging material or on the devices Refer to the previous section “Wet Packs” for information on how to manage problems related to moisture in or on packages. All occurrences must be reported to the supervisor who will determine if any or all of these indicators are significant enough to require a product recall. Refer to Module 12 Quality Systems for information about recalls. © Vancouver Community College 45 Medical Device Reprocessing Theory Modules Module 9: Sterilization 8. Low Temperature Sterilization Methods While most reusable medical devices have been designed to be compatible with steam sterilization, there are some that are not. Some types of electronics and synthetic materials that are used to make complex devices may be damaged by the high temperatures or the moisture of steam. To sterilize those types of devices, chemical sterilization methods have been developed. The common chemical sterilants that are used are: 1. Hydrogen peroxide vapour/gas plasma 2. A combination of Ozone and hydrogen peroxide vapour 3. Ethylene Oxide gas 4. Peracetic acid liquid While all MDRD’s use steam for sterilization, these chemical methods are not as common. And departments that require chemical sterilization wi

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