Studies in the early 1970s suggested that wrapped surgical trays remained sterile for varying periods depending on the type of material used to wrap the trays. Safe storage times for sterile packs vary with the porosity of the wrapper and storage conditions (e.g., open versus closed cabinets).  Heat-sealed, plastic peel-down pouches and wrapped packs sealed in 3-mil (3/1000 inch) polyethylene overwrap have been reported to be sterile for as long as 9 months after sterilization. The 3-mil polyethylene is applied after sterilization to extend the shelf life for infrequently used items.  Supplies wrapped in double-thickness muslin comprising four layers, or equivalent, remain sterile for at least 30 days.  Any item that has been sterilized should not be used after the expiration date has been exceeded or if the sterilized package is wet, torn, or punctured.

Event-Related Storage:

Although some hospitals continue to date every sterilized product and use the time-related shelf-life practice, many hospitals have switched to an event-related shelf-life practice.  This latter practice recognizes that the product should remain sterile until some event causes the item to become contaminated (e.g., tear in packaging, packaging becomes wet, seal is broken).  Event-related factors that contribute to the contamination of a product include bioburden (i.e., the amount of contamination in the environment), air movement, traffic, location, humidity, insects, vermin, flooding, storage area space, open/closed shelving, temperature, and the properties of the wrap material.  There are data that support the event-related shelf-life practice.  One study examined the effect of time on the sterile integrity of paper envelopes, peel pouches, and nylon sleeves.  The most important finding was the absence of a trend toward an increased rate of contamination over time for any pack when placed in covered storage.  Another evaluated the effectiveness of event-related outdating by microbiologically testing sterilized items.  During the 2-year study period, all of the items tested were sterile.  Thus, contamination of a sterile item is event-related and the probability of contamination increases with increased handling.

Dos and Don’ts:

Following the sterilization process, medical and surgical devices must be handled using aseptic technique in order to prevent contamination. Sterile supplies should be stored far enough from the floor (8 to 10 inches), the ceiling (5 inches unless near a sprinkler head [18 inches from sprinkler head]), and the outside walls (2 inches) to allow for adequate air circulation, ease of cleaning, and compliance with local fire codes (e.g., supplies must be at least 18 inches from sprinkler heads).  Medical and surgical supplies should not be stored under sinks or in other locations where they can become wet.  Sterile items that become wet are considered contaminated because moisture brings with it microorganisms from the air and surfaces.  Closed or covered cabinets are ideal but open shelving may be used for storage.  Any package that has fallen or been dropped on the floor must be inspected for damage to the packaging and contents (if the items are breakable).  If the package is heat-sealed in impervious plastic and the seal is still intact, the package should be considered not contaminated.  If undamaged, items packaged in plastic need not be reprocessed. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

ATS, Inc. stocks sterile-processing packaging supplies such as sterilization pouches or bags – see Supplies.