IAHCSMM Ch 14 High Temperature Sterilization

Gravity Air Displacement Sterilizers

passive air removal. steam enters chamber and forces cooler air to bottom of chamber and out of chamber drain. Steam enters the chamber and forces coolest air to bottom of chamber and out the drain, because air is heavier than steam.

The atmospheric room pressure at sea level is ??? pounds per square inch (psi)

14.7 psi

Exposure

After the desired temperature is reached, the sterilizer's control system begins timing the cycle's exposure phase.

Conditioning

At the beginning of the sterilization cycle, steam enters the upper back portion of the sterilizer. As steam enters, air is displaced through the drain. As steam continues to enter the sterilizer's chamber, pressure begins to rise, as does the steam temperature.

Exhaust

At the end of the exposure phase, the chamber's drain is opened and the steam is removed through the discharge line. This creates a void in the chamber; filtered air is gradually reintroduced into the chamber and gradually returns to normal room pressure.

Wet Pack problems identified by qualified sterilizer service technician.

Broken valves Malfunctioning steam traps or drain check valves. Faulty sterilizer gauges or controllers. Clogged drain line. Faulty drain valves.

A saturated steam sterilization cycle has at least three (and possibly four) phases:

Conditioning Exposure Exhaust Drying (in most instances)

4 Conditions required for effective Steam Sterilization

Contact, Temperature, Time, Moisture

Chamber drain is located

Front or center of the floor. Must be cleaned at least daily, and more often, as needed. Debris in the chamber drain can impede cycle performance.

Wet Packs caused by sterilzer

Gasket not completely intact. Clogged chamber drain strainer.

Immediate Use Steam Sterilizers

IUSS are located in ORs, surgical suite substerile rooms, Labor and Delivery units and special procedure areas that perform invasive procedures. Their intended use is for emergency sterilization of instruments when there is not enough time for terminal sterilization. No dry time, so sterilized instruments are hot and wet.

When sterilization is complete, follow the sterilizer IFU for opening the door. When cart is removed...

It should be placed in a low-traffic area where there are no air conditioning or other cold air vents in close proximity. For sterilizers without carts, items should remain in the sterilizer chamber until properly cooled.

CS departments typically use...

Jacketed sterilizers. The interior chamber walls of the sterilizer are heated by steam in the metal jacket to minimize condensation. The outside of the jacket is covered with insulation to help prevent condensation from forming on the jacket's outer and inner walls. This insulation also provides a safety feature because it reduces the likelihood that personnel working behind the sterilizer will be burned.

Dry heat sterilization is seldom used because...

Length exposure time is required

Steam is the sterilant of choice for several reasons

Low cost, Rapid sterilization cycle, Relatively simple technology, Leaves no chemical residues or byproducts

The door gasket is designed to...

Maintain a tight seal that prevents steam from escaping from the chamber and air from entering the chamber.

Extended Sterilization Cycles

Medical instrumentation manufacturers are now incorporating complex designs and materials. They may provide written processing instructions that lengthen the exposure phase of the steam sterilization cycle.

Packages are considered wet when...

Moisture in the form of dampness, droplets or puddles of water are found on or within a package after a completed sterilization cycle. Moisture can create a pathway for microorganisms to travel from the outside to the inside of a package.

If any moisture is present on or in one pack, the problem may be isolated to that one set. To ensure the problem is isolated to only one pack...

Other packs in the load may be opened to check for moisture. If there are several wet packs from one load, the entire load should be considered "wet." Wet packs cannot be released and should be reported for immediate follow up. Wet packs are considered contaminated and must be completely repackaged and reprocessed. All wet packs should be documented.

The weakest part of a steam sterilizer...

The door. It has a safety locking mechanism that automatically activates when chamber pressure is applied and it can only be unlocked when pressure is exhausted.

Contact

The most common reason for sterilization failure is the lack of contact between steam and the entire surface of the device being sterilized. This failure may be related to human error or mechanical malfunction. Not clean Sets too dense or poor positioning Packages wrapped too tight Loads too crowded Clogged drain strainer Mechanical malfunction Utility malfunctions

Bioburden

The number of microorganisms on a contaminated object; also called "bioload" or "microbial load."

Gauges and Controls (Monitors)

The sterilizer's gauges and/or controls (monitors) provide a visual and written record of sterilization conditions. CS Techs must check them throughout the sterilization cycle to ensure parameters are met. A printout form usually contains the following information: - Date and Time the cycle began - Selected cycle parameters, such as type of cycle, sterilization temperature and dry times. - A written record of actual cycle activities

Factors that impact effectiveness of sterilization methods

Type of microorganisms present; some microorganisms are more resistant to the sterilization process. The design of the medical device; complex devices present a challenge to the sterilization process. The number of microorganisms (bioburden) present; when there are more microorganisms on a medical device, the sterilization process becomes more difficult. The amount and type of soil present; soil acts as a shield to protect microorganisms.

Wet Pack problems caused by reasons outside of CS

Steam quality that does not meet the requirements of the sterilizer. Blocked steam lines. Boiler feed water that contains too many non-condensable gases, including air. Boiler not properly maintained. Malfunctioning steam traps or check valves. Poorly engineered steam piping. Increased demands for the steam supply. Placing hot load in air conditioned area or area with humidity over 70%.

Temperature

Steam sterilization must occur at specific temperatures. These temperatures are needed to kill heat-resistant bacteria. The two most commonly-encountered temperatures for steam sterilization are: Gravity sterilization 250F and Dynamic air removal 270 - 275F

Time

Steam sterilization need adequate amount of time of steam contact to be effective.

Saturated steam

Steam that contains the maximum amount of water vapor. Saturated steam acts similar to fog because it holds many tiny water droplets in suspension. Saturated steam is similar to air with 100% r.h. When saturated steam cools, water condenses as a liquid

The most frequently used sterilant for devices not adversely affected by moisture or heat is...

Steam. Safe, Effective, Reliable, Low cost

High temperature sterilization is achieved by...

Subjecting items being processed to thermal energy from moist heat (steam) or dry heat.

One of the concerns with steam sterilization is super-heated (dry) steam

Super-heated steam reaches higher temperatures than saturated steam, and due to lack of moisture, it is a poor sterilant. If steam is not saturated (less than 97% to 100% r.h)... Items in sterilizer will remain dry and microorganisms cannot be killed as readily under wet conditions Items in sterilizer will remain "cool" much longer, especially if they are wrapped. Saturated steam is a better "carrier" of thermal energy than dry air.

Tabletop Sterilizers

-Frequently used in clinics and dental offices. -Use electricity to heat water into steam. Water quality is specified in IFU. In a tabletop sterilizer, steam rises to the chamber's top and as more steam is produced, air is forced out through the drain near the bottom of the chamber. When steam enters the drain, a thermostatic valve closes, which causes the steam to build up pressure until the operating temperature is reached. When the proper temperature is reached, the timer is activated. At the end of the cycle, the relief valve opens to allow the steam to escape. The steam passes through the water reservoir where it condenses back to water. After pressure drops to zero, the door can be opened.

Guidelines for cleaning and maintaining sterilizers

Cool the chamber before performing any cleaning or maintenance procedure. The chamber drain strainer should be removed at least daily and cleaned thoroughly under running water using a non-abrasive brush and a mild detergent. The inside of the chamber should be cleaned according to manufacturer's instructions. Residue buildup on chamber's interior can affect the cycle's drying ability. Clean residue with nonabrasive and nonlinting products. Rinse detergent and residue from the chamber thoroughly to avoid deposits on devices during sterilization. Door gasket should be inspected and wiped clean daily with a clean damp nonlinting cloth. Carriages, carts, and loading baskets should be routinely cleaned with a mild solution. Ensure they are not damaged. Follow instructions about need and method for cleaning and flushing the chamber's drain. Air and steam will not pass efficiently if the drain line is blocked. Strong abrasives or steel wool should never be used on the sterilizer because they can scratch the surface and encourage corrosion. Inspect recording devices daily, including paper charts and printer paper.

To unload sterile items...

Do not unload packages before they are cool. Placing hot or warm packages on cold surfaces will cause condensation to occur beneath and/or between them. If warm packages are placed in plastic dust covers, condensate will be trapped until opened and the moisture may damage items protected by the dust cover. Handle the sterile packages as little as possible. Items should not be moved or touched until they have cooled to room temperature.

Moisture

Dry, saturated steam is required for effective steam sterilization. Saturated steam is similar to fog because it holds many tiny water droplets in suspension. The moisture content of saturated steam should possess a relative humidity (r.h.) of 97% to 100%

Drying

Drying begins at the conclusion of the exhaust phase. Dry times are based on device, packaging and sterilizer's IFU

Prevacuum Steam Sterilizers

Dynamic air removal cycle depends on one or more pressure and vacuum sequences at the beginning of the cycle to remove air during the preconditioning phase. Typical Temp: 270-275 F

Causes of wet packs

Packs that were improperly prepared or loaded incorrectly for sterilization. This is the most frequent cause. Heavy or dense instrument sets. Not using absorbent material to wick moisture between heavy metal, such as basin sets. Textile packs wrapped too tightly. Improperly prepared items, such as items wrapped while moist. Metal items positioned in a way that allows water to pool or trap steam. Linen packs wrapped too tightly, causing them to retain moisture. Improper placement of concave items, such as medicine cups, in a position that does not allow for drainage. Not using the correct filters or incorrect filter placement on a container.

Steam-Flush Pressure-Pulse Sterilizers

SFPP sterilizers use a repeated sequence of a steam flush and pressure pulse to remove air from the sterilizing chamber and processed materials. Air removal occurs above atmospheric pressure; no vacuum is required.

The load contents should be visibly free of

liquid. Water droplets on the outside of packages or on the rails of carts are signals that every item in the load should be visually inspected. Do not touch items during visual inspection. Wet items should be considered contaminated.

Thermostatic Trap

located in the drain line, coolest place in sterilizer, a sensor in the trap measures steam temperature, and automatically controls the flow of air and condensate from the sterilizing chamber.

To ensure full steam contact and removal of air, the sterilizer must be...

properly loaded to allow adequate air circulation and drainage of the condensate. - Allow for proper steam penetration and avoid overloading. Packages must be placed for efficient air removal, steam penetration and evacuation. - If a shelf liner is used, it should only be made of absorbent material. - Solid containers must be positioned so air can exit and steam can enter. - There should be visible space between packs to allow steam circulation and drying. - When combining loads, place hard goods on the bottom to prevent condensation from dripping onto lower packs. - Packages must not touch chamber walls. - Basin sets should stand on edge. They should be tilted for drainage, so if water is present, it will run out. - Position textile packs so the layers within them are perpendicular to the shelf. - Stand paper/plastic peel pouches on edge using a basket or rack. Placing them plastic side down may cause moisture to remain inside, and placing them plastic side up may cause water to stand on top of the plastic. Place the sterilization pouches paper-to-plastic for air and steam circulation. - When possible, sterilize textiles and hard goods in separate loads. If not, place textiles on top shelves and hard goods below to avoid condensation runoff from the hard goods onto the textiles below. - Surgical instrument trays with perforated bottoms should sit flat on the shelf to maintain even instrument distribution and to facilitate proper drainage.

Dynamic Air Removal Sterilizers

similar to gravity air displacement sterilizers except vacuum pump or water ejector removes air during preconditioning phase prior to reaching exposure temperature and they usually run at higher temps Temps 270-275F