Sterility Duration

A frequently asked question in CS and SPD departments is, “After being sterilized, how long do instruments remain sterile?” Regretfully, organizations such as the CDC and the JCAHO do not provide the answer to this important question. At present, it is left up to each individual healthcare facility to determine their shelf life protocols regarding sterile packs and trays and if the sterility of their packs and trays are ‘event’ related or ‘date’ related. When it comes to shelf life protocols, most facilities use the ‘event’ related standard and they recognize that sterile packs and trays are ‘sterile’ until an event occurs that affects the sterilization of the instruments. Regardless of the protocol chosen, the healthcare facility should clearly spell out the practices that the facility will follow relating to event related sterility status. A number of years ago a New York hospital was doing some renovations. Behind a bricked-in wall they found a small storage area that had been sealed off since 1927. Sitting on the shelves were dozens of instrument trays wrapped in paper. The infection control manager tested the trays and found that the instruments were still sterile after 70+ years of sitting on the shelf. This is an excellent example of sterility being ‘event’ related and not ‘time’ related. In 1983 the CDC published recommended storage times for various sterile packs. Those recommendations are still followed by many healthcare organizations. The CDC’s recommended shelf-lives are considered too short by the majority of healthcare facilities. Their reason for rejecting the CDC’s recommendations is that a lot of valuable labor, expensive supplies, resources and time are wasted by reprocessing perfectly good sterile packs and trays. The majority of U.S. healthcare facilities have adopted the concept that sterilized medical items have an ‘event’ related shelf life. Under this widely accepted concept, it is acknowledged that sterile medical instruments have an indefinite shelf life and will remain sterile, unless they become contaminated due to an external event (i.e., torn or wet packaging). This concept has been supported by numerous organizations, studies and papers over the years. In looking at AAMI ST79 we see that “the shelf life of a packaged sterile item is event-related and depends on the quality of the packaging material, the storage conditions, the conditions during transport, and the amount of handling. There should be written policies and procedures for how shelf life is determined and how it is indicated on the product.”¹ And from the AORN we read that “the shelf life of a packaged sterile item should be considered event-related. [1: Strong Evidence] The sterility of an item does not change with the passage of time, but may be affected by particular events (e.g., amount of handling) or environmental conditions (e.g., humidity).”² All sterile packaging systems (rigid containers, wraps etc.) are required under FDA 510(k) clearance regulations to have a shelf life stated and then tested to that shelf life if they are a terminal sterilization packaging system. A majority of sterile packaging systems have at a minimum a six month shelf life and most have a one year shelf life. However, this is only a factor if you are not an event related facility. If you are an event related facility you don’t have to recognize the stated shelf lives of packaging systems as they are noted in their IFUs. Healthcare facilities must decide upon an event related or a date related policy in order to manage the process and ensure the sterility of the packs and trays. Every facility should have an established, written policy so that the shelf life of packaged sterile items is addressed on the basis of handling, the conditions during transport, the quality and type of the wrapped material along with the storage conditions. Care needs to be taken during the processing of sterile packs and trays so that contamination of the instruments can be avoided during storage. After storage and before transport to surgery, the packs and trays must be inspected for dryness and integrity to ensure the sterility of the instruments. Regardless of which policy your facility uses, always remember that if your instruments aren’t clean (i.e., free of bioburden) prior to sterilization, your instruments aren’t sterile. The best way for your facility to ensure clean, sterile, moisture-free instruments on every reprocessing cycle is to only use instruments whose cleaning IFUs have been validated using FDA validation protocols. 1. ANSI/AAMI ST79 2010 & A1:2010 & A2:2011 & A3:2012 & A4:2013, 8.9.3, page 88 2. AORN Guidelines for Perioperative Practice, 2017, Guidelines for Selection and Use of Packaging System for Sterilization, Recommendations III. D., page 854