Processing contaminated instruments

June 1, 1997
Overloading a sterilizer can have serious outcomes. It increases the risk of not sterilizing all the instruments in the chamber.

Overloading a sterilizer can have serious outcomes. It increases the risk of not sterilizing all the instruments in the chamber.

Chris Miller

Questions continue to arise concerning procedures for processing contaminated instruments. Here are the answers to some of the most often-asked questions

__ If I properly clean, bag, tape, and autoclave an instrument, at what point in time does the sterilization of the unopened bag expire?

The shelf life of sterile instrument packages or cassettes depends on how those items are stored and handled after being removed from the sterilizer. Thus, shelf life is event-related rather than time-related. Instrument packaging should be carefully checked just before the instruments are unwrapped for use. If the packaging material is torn, punctured, or has gotten wet, then the sterility of the contents is compromised and the instruments need to be repackaged and resterilized.

Sterile packages and cassettes should be handled as little as possible before distribution at chairside. They should not be handled at all after autoclaving until they are dry. They should be stored in a dry, low-dust area and used on a first-in, first-out basis. Sterile packages should not be stacked upon each other during storage; this increases chances for packages to puncture from compression. Shelves for cassette storage should be free of splinters or other defects that may tear the cassette wrap.

__ Is it OK to remove instrument packages from the autoclave and let them dry on the countertop?

Packages and wrapped cassettes are wet after autoclaving, making the wraps and paper packaging material very vulnerable to tearing if handled. Also, contaminants may settle on the outside of a wet package and be wicked through the packaging material. Some autoclaves have a post-sterilization dry cycle that allows the packages to dry while they are in the sterilizer chamber. Alternatively, the autoclave door can be opened at the end of the regular cycle and left ajar for 20-30 minutes to dry the packages.

__ If we place packaged sterile instruments on the tray at chairside and the doctor doesn`t use them, can we put them back in the instrument storage drawers until they are needed again?

Since the package may have become wet from patient spatter, touched with contaminated gloves, or accidentally punctured during patient care, the items should be completely reprocessed.

__ Do we have to wrap instrument cassettes before autoclaving?

Yes. One of the basic functions of instrument cassettes is to contain the instruments through the cleaning and sterilizing procedures, minimizing the direct handling of contaminated instruments. Thus, the cassette must contain holes to allow the cleaning solution and the sterilizing agent to reach the instruments. Unfortunately, the holes also allow dust and airborne contaminants to enter and contact the instruments after sterilization if the cassettes are not wrapped.

__ Can we put metal boxes of endo files in our autoclave?

Sterilization failure often occurs when the sterilizing agent (e.g., steam, hot chemical vapor) is prevented from directly contacting the items to be sterilized. Appropriate sterilization pouches and wraps permit steam and hot chemical vapor to penetrate to the instruments. Tightly closed, solid containers do not. In some instances, a closed container may permit sterilization of its contents in a dry heat sterilizer. However, this should be confirmed by using a biological indicator (spore test) inside the container.

__ How can I keep burs from rusting in the steam autoclave?

Carbon steel burs that rust in a steam sterilizer can be sterilized without rusting in a dry heat or unsaturated chemical vapor sterilizer.

__ Should our office be using indicator strips in addition to spore-testing our sterilizers?

Chemical-indicator strips contain special inks that change color when exposed to certain high temperatures or other sterilizing conditions. Some (e.g., "autoclave tape," the special markings on sterilization pouches, and some strips) will change quite rapidly when the sterilizing temperature is reached. These usually are referred to as process indicators. Others, referred to as integrators, change more slowly after a combination of temperatures and time/presence of steam is achieved. All chemical indicators can be read as soon as the packages are removed from the sterilizer, giving an immediate visual indication that the packages have been processed.

Chemical indicators on the outside of packages or cassettes help prevent the accidental intermingling of sterile and nonsterile items. A quick glance at such packages brought to chairside helps assure that the instruments have been processed through sterilization and are ready to use. Also, the use of chemical indicators provides a means of monitoring the sterilization process between those times when spore-testing is performed.

__ We have a small autoclave and have to run it several times a day. I`m afraid I`m overloading it, but we need to turn over the morning instruments for the afternoon appointments. Do you have any suggestions?

Purchase a second or a larger sterilizer. Overloading a sterilizer can have serious outcomes. It increases the risk of not sterilizing all of the instruments in the chamber. A sterilizer cycle is preset and allows a specific amount of time for the steam to contact all surfaces to be sterilized and to stay in contact with those surfaces. Overloading can prevent steam from contacting some instruments, as well as remain in contact for a prescribed time.

Operating manuals have instructions for the proper loading of the chamber. If the manual is not available, a general rule is to place packages and cassettes on their edges rather than stack them one on top of the other. This allows for a better natural separation of the items and better access to the steam, dry heat, or hot chemical vapor.

Concerns about loading a sterilizer can be addressed by placing a spore-test inside three or four packages and placing the packages in different parts of the load, including one in the center. Run a normal cycle and then analyze the spore tests.

Chris Miller is director of Infection Control Research and Services and professor of oral biology at Indiana University.