In health care, various methods are used to sterilize devices. In addition to the common process of using steam, such methods as dry heat, ethylene oxide, ozone, and, in commercial settings, radiation, are also used to sterilize devices. No one method can sterilize all devices, which can make for some interesting problems for health care. Some of the sterilizing agents are hazardous to the environment and the people doing the work. Before sterilizing any device, be sure to use the correct precautions.
In the hospital setting, the most common sterilizer is the steam autoclave. Many hospitals will have an ethylene oxide unit. Ozone units and the liquid systems (peroxide and RF), called Sterad, are making some inroads. In the endoscopic and respiratory areas, “cold sterilization” is common using various liquids. Some contend that cold sterilization is closer to pasteurization than sterilization.
Sterile is defined as, “The absence of all forms of life, cells, viruses, and spores.” Sterilize is defined as, “The use of physical or chemical procedures to destroy all microbial life, including bacterial endospores.” While this sounds simple, the procedures can be very involved with many presteps needed to prepare the items for sterilization before being placed into the chamber. In most hospitals, sterilizers are located in a central area, often called central supply, where the staff prepares contaminated devices by rinsing them, putting them into an ultrasonic cleaner, and then wrapping them in a special paper. In some settings, the cleaned and unwrapped items are placed in a special container before being placed into the sterilizer. For gas sterilization, the devices are usually placed in pouches instead of being wrapped.
A steam sterilizer, sometimes called an autoclave, can vary in size from a small benchtop unit up to a very large unit that is loaded with forklifts. Most units that the biomed comes in contact with fall on the lower end of the sizes. A common chamber is about 30 inches square and 24 to 48 inches deep. The chamber is made of corrosion-resistant steel that is not affected by the temperature and pressures that are generated during the sterilization process. The bigger units will have two doors: one on the “dirty” side, where the washed and wrapped devices are loaded, and the other on the “clean side,” where the packs are removed and placed onto shelves for reuse. It is important to remember that this area has a clean and dirty side; and as a biomed doing service to the units, you have to know which is which so you do not contaminate items.
The most common autoclaves run at 121°C or 250°F with a pressure of 15 PSI, for 15 to 20 minutes after the chamber reaches this temperature. It can take several minutes for the chamber to reach the needed temperature. Once the set temperature is reached, it is held for the allotted time. To speed up the process, some units have a vacuum pump that draws air out of the chamber, which provides better penetration of the steam into the packs. After the temperature has been maintained for the set time, the steam is turned off and the vacuum pump draws any residual steam from the chamber while the retained heat dries the packs. The packs must be dry before removal from the chamber as any moisture will attract microbes in the outside air and will contaminate the packs. The drying time can vary up to 30 minutes after the steam is shut down. If the operator is complaining of wet items, there may be problems with the venting or vacuum systems.
In many operating-suite core areas, there are several “flash” autoclaves. These are steam units that operate at both a higher pressure and temperature, 270°F at 29 PSI. Once the chamber temperature is reached, sterilization time is 4 minutes. In these units, the instruments are often placed in trays and not wrapped. This allows for a rapid turnaround of the instruments.
In most hospitals, both types of sterilizers get their steam from the hospital steam generators located elsewhere in the hospital building. If the piping run is too long, the temperature of the steam may drop and a heater will be required to increase the temperature to acceptable levels. While not common, these heaters can cause problems with the sterilization process if they are set too low.
In nonhospital settings, there may be no central steam generation, so the sterilizer will have an internal steam generator. While the unit works the same, there are added failure and preventive maintenance (PM) points that need to be considered with these units. The quality of and the minerals in the water used to make the steam can result in scale buildup, discoloration of the packs, and more valve replacements than expected. Depending on the minerals in the water, you may have to “descale” the unit every year. This is a simple process, but it takes time. The replacing or rebuilding of the valves is an ongoing expense that must be taken into account and planned for to keep the units running properly.
The benchtop unit generates its own steam, generally has no vacuum draw down of the chamber, and is used for unwrapped instruments. Even though the unit is small, it still has many of the same problems that the larger ones have.
Common Problems With Sterilizers
As previously mentioned, valves need attention on a regular basis. The published PM procedures from the manufacturer should be followed, unless experience on that particular unit indicates that the interval can be stretched or should be shortened. Temperature monitoring and recording is automatic on most large units, and the printout system—whether dot matrix or pens—needs attention on a regular basis. Gaskets and latches wear out and should be replaced as needed. If the door is leaking steam, it could be a gasket or door-alignment problem; sometimes, it is just loose hardware on the door hinge.
In some areas, water-conservation devices are placed on autoclaves. These tanks and valves also have to be checked during the PM process. Remember that steam sterilization is not for all items. Rubber, most plastics, and anything with electronics should not be autoclaved. There are several disadvantages to autoclaves, such as corrosion on instruments and dulling of the finish.
Last, be careful when working on sterilizers, because burns are common. Be sure the steam is off and the unit has cooled down before working on sterilizers.
David Harrington, PhD, is director of staff development and training at Technology in Medicine (TiM), Holliston, Mass, and is a member of 24×7’s editorial advisory board. Contributing to this article is John Downs, sterilizer specialist with Technology in Medicine.
1. In a typical steam sterilizer, how long is the sterilize time once the chamber reaches the desired temperature?
a) 3 to 5 minutes
b) 15 to 20 minutes
c) 60 minutes
d) 15 to 20 seconds
2. In a “flash” sterilizer, what is the typical sterilize time once the chamber reaches the appropriate temperature?
a) 1 to 2 minutes
b) 45 seconds
c) 10 minutes
d) 4 minutes
3. If a sterilizer door is leaking steam, what could be the problem?
a) A leak in the gasket
b) The door is misaligned
c) It is of no concern
d) A or b or both above
4. Nonflash autoclaves operate at?
a) 121°F and 50 PSI
b) 250°C and 15 PSI
c) 121°F and 15 PSI
d) 121°C and 15 PSI