* Reviews the characteristics of the ideal sterilization wrap.
* Provides guidance to infection control and central processing professionals in choosing an appropriate wrap.
The use of sterile surgical instruments is a keystone of surgery. Guidelines from the Centers for Disease Control and Prevention recommend that all surgical instruments should be sterile.1 For more than 75 years, hospitals have been packaging surgical instruments to maintain sterility until instrument use. The sterilization wrap must provide protection against contact contamination during handling and must provide an effective barrier to microbial penetration.
Current Use of Sterilization Wraps
There are several choices in methods to maintain sterility of surgical instruments including rigid containers, peel pouches of plastic and/or paper, and sterilization wraps (woven and nonwoven). While most hospitals use all of these packaging options, the most commonly used method is sterilization wraps.
The original sterilization wraps were 140-thread count muslin cloth. Advantages of these cloths included that they were soft, reusable, inexpensive, absorbent, and drapeable (i.e., able to drape easily over trays). An important disadvantage was that the cloth was woven and, hence, did not provide complete protection against microbial penetration. To minimize microbial contamination of the instruments inside, hospitals initiated double sequential wrapping.
In the 1960s, nonwoven materials were introduced and provided an effective tortuous path that protected against microbial contamination and, when treated, provided liquid resistance capability. However, the material used for these wraps was derived from cellulose and did not possess adequate strength. Hence, sequential wrapping still remained necessary. The introduction of polypropylene allowed the development of wraps that possessed strength, barrier, and repellent properties.
Currently, a popular product offering uses a layered design consisting of spunbond/melt-blown/spunbond (SMS) layers. This fabric consists of three thermally bonded layers; "spunbond" provides the strength and "meltblown" provides the barrier. These multiple layers provide excellent protection from microbial contamination.2
In central processing, double wrapping can be done sequentially or non-sequentially (simultaneous wrapping). The sequential wrap uses two sheets of the standard sterilization wrap, one wrapped after the other. This procedure creates a package within a package. The non-sequential process uses two sheets wrapped at the same time so that the wrapping needs to be performed only once. This latter method provides multiple layers of protection of surgical instruments from contamination and saves time since wrapping is done only once. Multiple layers are still common practice due to the rigors of handling within the facility even though the barrier efficacy of a single sheet of wrap has improved over the years.
Evaluating Shelf Life
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.3-4 Microorganisms were found to penetrate single-wrap muslin as early as three days, and double-wrap muslin and single-wrap two-way crepe paper in 21 to 28 days when stored on open shelves.3 Based on these studies, the Joint Commission on Accreditation of Hospitals (now Joint Commission of Healthcare Organizations) required that hospitals provide an expiration date on wrapped surgical trays, indicating a time when the trays would no longer be considered sterile. In a 1984 article, Mayworm criticized the scientific basis for dating sterile surgical trays. He noted that "time doesn't contaminate products, events do."4 He then listed the following factors, which contribute to the contamination of product: bioburden (contamination in the environment), air movement, traffic, location, temperature, humidity, and the barrier properties of the wrap material. He stressed that when the proper wrap materials along with appropriate sterilization techniques were used, surgical trays should remain sterile unless damaged. Subsequent studies demonstrated that the sterile integrity of surgical packs was maintained for at least one year and no trend was found toward increased probability of contamination over time.5 In this latter study, no differences were observed among the wrapping materials studied (i.e., two-ply reusable, nonbarrier wovens, both new and previously used; disposable, barrier nonwovens; and paper/plastic peel pouches). These studies were conducted under ideal circumstances. Sterility may be more difficult to maintain under actual use conditions where movement and storage conditions may damage wrap materials.6
Characteristics of an Ideal Wrap
The characteristics of an ideal wrap are listed in Table 1.7,8 Key characteristics include the ability to allow the sterilizing agent (e.g., steam, ethylene oxide, hydrogen peroxide gas plasma) to penetrate and then to provide a barrier, which maintains sterility of the wrapped surgical instruments. Failure to allow the instruments to be sterilized and then to maintain their sterility may result in surgical site infections, clearly an unacceptable outcome. Other important desirable characteristics include drapeability, puncture resistance, resistance to tearing, liquid resistance, flexibility, non-reactive, non-linting, non-toxic, stable, no odor, easy to use, transparency, non-restrictive waste disposal, and low cost in use.
Evaluating a Sterilization Wrap
In evaluating wrap products, professionals should evaluate the products based on performance characteristics. The data provided on products should be based on standardized tests and, when possible, be confirmed by independent laboratories. Products may not possess all the characteristics of the "ideal" wrap. Professionals may need to balance the importance of individual characteristics. The intended use of the product in the professional's facility must be assessed. Lastly, the cost and time of training personnel must be considered in the decision to purchase a new product.
Table 2. Questions to Ask in Evaluating a Sterilization Wrap
Currently available products for wrapping surgical instruments are clearly superior to older products. The characteristics of an ideal wrap are well described. Professionals must evaluate individual wraps based on intended use in their facility. New wrap materials are constantly being introduced into healthcare; however, they should be evaluated by using the guidelines provided in this paper.
William A. Rutala, PhD, MPH, and David J. Weber, MD, MPH are from Division of Infectious Diseases, University of North Carolina (UNC) School of Medicine and the Department of Hospital Epidemiology, UNC Health Care System (Chapel Hill, NC). This paper was supported, in part, by an educational grant from Kimberly-Clark. The authors would like to thank Jan Schultz for reviewing this article.