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What do you need to know before purchasing a steam sterilizer?

Disinfection is the process of retarding the growth or destroying certain micro-organisms. This process is effective for most organisms except large numbers of spores and viruses and is not equivalent to sterilization. Sterilization utilizing steam or low temperature sterilization is the only ways to achieve terminal sterilization. All reusable patient equipment must be appropriately decontaminated; cleaned, disinfected or terminally sterilized dependant on what the device will be used for. All critical devices that come in contact within the normally sterile sites of our skin must be terminally sterilized. Consider having surgery and the surgical instrumentation were used on a previous patient and were not cleaned and properly sterilized. The potential for infection or possibly death is mind-boggling. This is the reason why steam sterilizers play such an integral part in departments such as Sterile Processing where all the processes of decontamination, disinfection and sterilization take place.

When procuring a steam sterilizer for your Sterile Processing Department, what do you really need to know about it? Prior to discussing what a steam sterilizer should do and what we should consider before making a purchase, the following definitions will be helpful:

1. Sterilant - A sterilizing agent; for example, steam at certain temperature, ETO, parecetic acid.

2. Sterile - Free from all microorganisms.

3. Sterilization- Destruction of all living organisms by exposure to physical or chemical agents.

4. Sterilizer- A device in which physical or chemical agents are introduced into a chamber containing medical products for the purpose of destroying all living organisms.

Sterilization by steam requires three important factors. Temperature, time and moisture. Steam sterilizers must achieve high temperatures ranging from 250 Fahrenheit for gravity displacement and 270 –275 Fahrenheit for flash and dynamic air removal sterilizers. These temperatures are normally pre-set by the sterilizer manufacturer. Sterilization times are based on manufacturer recommendations for different patient items. Adequate contact is also required for all types of sterilization. Sterilization time is measured utilizing a scientific factor called D-Value or decimal reduction time. This is the amount of time at the required temperature to kill 90% of micro-organisms. When an organism is reduced by 90% or 1 D, 10% of organisms remain. Each type of micro-organism will vary and therefore will have a different set of D-values. Within the steam sterilizer a spore or live bacteria called GeoBacillus Stearothermophillus is used to challenge the steam sterilizer. Although highly resistant, this spore is considered non-pathogenic. This spore is used with every implantable item and used weekly to test the steam sterilizer as per ANSI/AAMI ST 79 recommendations. (AAMI is the Association for the Advancement of Medical Instrumentation. AAMI makes recommendations to promote sterility assurance and is used to guide healthcare personnel in the proper use and processing of patient equipment.) After the spore challenges the sterilizer, it is incubated for a period of time at a certain temperature to allow growth. Once the results are negative, there is no growth and all quarantined implants can be released. This spore has a D-Value of two minutes at 250 Fahrenheit or twenty seconds at 275 Fahrenheit. What does this mean? It will take two minutes at 250 Fahrenheit or twenty seconds at 275 Fahrenheit to kill 90% of the micro-organisms present. It is agreed that sterilization within a hospital approved sterilizer, six D-Values are sufficient enough to kill all pathogenic micro-organisms. The second D-value will reduce micro-organisms by another 90% bringing the reduction to 99%. A third D-Value will achieve a 99.9% reduction and six D-Values will render the item 99.9999% sterile. It is important to follow the manufacturer’s recommendation. One tray may need a four minute cycle where another tray, much more complex may need a ten minute cycle.

Manufacturers base this process on a one half cycle. In other words, a 100% biological kill can be accomplished at one half of the recommended cycle. The manufacturer’s recommendations should always be looked upon as the absolute minimum set. As important as sterilization is, the first step - cleaning is the most important step. If an item is not clean, it cannot be sterile. Remember you can clean without sterilization, but, you cannot sterilize without cleaning. It is impossible to sterilize proteins such as blood, feces, hair and tissue. Bacteria like to hide in nooks and crannies; therefore, all gross matter must be removed from all objects prior to the sterilization cycle. Proper manual or mechanical action is required to properly remove any gross matter.

Before purchasing a steam sterilizer you must understand how a sterilizer functions and what it is you will be utilizing this sterilizer for. An understanding of certain factors upon which the principles of steam are based is necessary. These include: Time, temperature, contact, pressure, moisture and what you are sterilizing.

Additionally, some questions you should ask include:

1. What kind of controls is the sterilizer equipped with?

2. Does it have a computer control system?

3. Is there an error alarm?

4. Can the sterilizer be manually operated in case of a power interruption?

5. Is there a tamper proof control that can be set by the operator?

6. Is it compatible with the peel pouches, wraps, and containerized systems currently used within your facility?

7. What is the maintenance fee per year of operation?

8. Is there a warranty and how long is the warranty?

9. What is covered under the warranty?

10. What is the cost of installation?

Finally, does the company have a local representative that can help you and be available for you when assistance is needed?

You must be certain the sterilizer you will purchase is the best choice for your facility and for what you will be utilizing it for. A physical inventory of supplies and instrumentation should be conducted prior to making any purchase. Are these items steam compatible? Be aware certain scopes and instrumentation cannot withstand the high temperatures of steam sterilization. If this is the case you may want to look at the different options available to you utilizing low temperature sterilization. There are several to choose from such as ETO, Sterrad, Ozone and Parecetic Acid for just in time sterilization. Manufacturers are developing newer instrumentation and scopes compatible with the demands of high steam sterilization which is quick, inexpensive and safe when done correctly. Understanding steam sterilization will help all decision makers in the Procurement and Sterile Processing Departments make the best decision for their institution and their patients.

1. EPA Regulation: 40 CFR 141.14:141.21

2. "Aseptic Processing vs. Terminal Sterilization -The Effects on Sterile Formulation Development." Proceeding of the PDA/PMA Sterilization Conference. Washington, DC. 1990.

3. FDA "Guideline on Sterile Drug Products Produced By Aseptic Processing." Center for Drugs and Biologics. Rockville, MD. June, 1987

Recommended Reading:

Central Service Technical Manual, 6th Edition Chicago, IL

AAMI ST 79