Barrier Drapes and Their Impact on Surgical Site Infections
By Nathan L. Belkin, PhD
The need for surgical drapes to be made of barrier-quality materials is recommended on the basis of theoretical rationale, but it has not been supported by unbiased, statistically valid, conclusive research.
The use of surgical gowns and drapes has evolved as a standard of practice. Their primary purpose is to protect sterile surgical zones from microbial invasion. Reusable woven fabrics had been used universally as aseptic barriers since the turn of the century. The most popular and commonly used material was referred to generically as muslin (i.e., a loosely woven, all cotton, 140 -thread count fabric). The material was readily obtainable, easy to work with, economical and thought to be an effective bacteriological barrier.
It was not until 1952 when Beck alerted the surgical community that while muslin was deemed acceptable as a bacteriological barrier when dry, it lost its effectiveness once it became wet -- even when multiple layers were used. A review of the literature reveals this was the turning point that triggered research to develop more satisfactory materials for unique application.
One of the new products that became available was initially described as paper. Today they are known as single-use disposables. The producers of woven reusable materials responded to the need, igniting heated controversy between reusables and disposables that overshadowed the concern for patient welfare and the possibility of these products being able to reduce the incidence of surgical site infections (SSIs).
The Era of Barrier Materials
Intent on examining the impact draping materials have on SSIs, the American College of Surgeons' (ACS) Committee on the Operating Room Environment (CORE) issued a position paper challenging the textile industry to develop performance standards for these new barrier materials. CORE cautioned that the methods for testing and evaluating the performance capabilities of these materials should simulate what they described as "usual conditions of use."
For some time, most hospitals continued to use the traditional, loosely woven, readily permeable fabrics for their surgical gowns and drapes. Lacking scientific evidence to support the implementation of the new bacteriological barriers, the surgical community relied on industry's efforts to support their use.
Barrier Materials and SSIs
In the latest Guideline for the Prevention of SSI, the Centers for Disease Control and Prevention (CDC) reviewed a number of published studies in which researchers attempted to demonstrate whether or not the use of the new generation of barrier-quality materials could influence the incidence of SSIs. They concluded, "There is limited data that can be used to understand the relationship of gown and drape characteristics with SSI risk." As a result, it ranked their importance as Category 1B, which is described as "strongly recommended for implementation and supported by some experimental, clinical or epidemiological studies and strong theoretical rationale."
In a recent review of the same and a number of other studies dedicated to the same objective, the authors concluded the studies "have limited relevance because of methodological flaws and product improvements." It should be noted that of all the studies that appear in the literature, none reported having achieved a lower infection rate in clean cases than that reported in Cruse's classic 10-year study in which all the gowns and drapes were made of the "usual cotton material."
Interpreting the Barrier Studies
Notwithstanding the results reported in any of the studies, detailed information about a number of vital factors all but prohibit their interpretation and a reasonable conclusion. For example:
1. Since gowns and drapes used were made of a barrier material, they failed to show whether it was the gown, the drape or the combination of the two that accounted for the results.
2. The studies did not take into consideration the influence of other factors described by Laufman as the five "Ds": Discipline of the surgeon; design of the surgical suite; defense mechanism of the patient; drugs (prophylactic antibiotics); and a myriad of other devices used.
3. There is no information regarding the performance capability of barrier effectiveness of the materials of which the gowns and drapes were made.
Testing for Barrier Effectiveness
The introduction of the new generation of barrier materials was accompanied by a variety of test methods, with every manufacturer using one that best suited its purpose. As an industry, the non-woven segment ultimately adopted its mason-jar test method that their trade association had developed. The woven, reusable manufacturers used one of several existing test methods that had been used for rainwear fabrics.
When the publication of two studies that examined the effectiveness of some of the new materials -- one by Laufman and another by Schwartz -- disclosed that many of the alleged barrier materials permitted what Laufman identified as strike-through, the industry retreated to its drawing board.
The Need for Protective Gowns
With the emergence of the era associated with the transmission of bloodborne pathogens, the surgeon's gown suddenly acquired an additional role - protecting the members of the surgical team from the patient. Notwithstanding the need for a universally accepted test method, this also meant that whatever degree of strike-through may have been experienced in the past was no longer to be tolerated.
It was during this period that two clinical researchers, Shadduck and Nichols, working independently of one another, reported on the results of their examination of a variety of barrier materials. The need for a standard test method became evident when some of the materials found to be satisfactory under the conditions of Shadduck's test would have failed when subjected to the challenge of the device used by Nichols.
Not to be overlooked is the importance of the findings of the Quebbeman and Telford in-vivo evaluation of surgical gowns demonstrating the level of barrier protection was contingent on the level of exposure, or as was later stated by the Occupational Safety and Health Administration (OSHA)'s final standard as the "level of exposure anticipated." Thus it was reasonable to believe that whatever test method would be adopted would express a material's protective capability on a comparative basis.
The Level of Anticipated Exposure
With a pressing need for a test method, the American Society for Testing Materials (ASTM) announced the development of a new mechanical device to fill the void. Under the provisions of F1670-95, a material was first to be tested for its resistance to liquid penetration. If it passed that test, it qualified to be tested for its resistance to viral penetration under the provisions of F1960-95.
The results are reported as pass/fail rather than on a comparative basis. Furthermore, the test methodology tends to characterize a material as being liquid-proof and/or impervious. Actually, the "pass" is predicted on a fabric's ability to withstand penetration at a challenge of 2 pounds per square inch (psi) which is contrary to what has been reported in the literature.
For example, under in-vivo conditions, Smith and Nichols reported pressures to be as high as 2.9 psi; Telford and Quebbeman discovered gowns that had passed the ASTM's test permitted varying amounts of strike-through; Ahman, et. al, reported experiencing penetration through gowns made of plastic laminated materials; and Leonas found that a material known as having passed both of the ASTM's tests failed in an in-vitro situation when tested under far less of a challenge than 2 psi.
The ASTM's tests are titled, "Standard Test Method for Resistance of Materials Used in Protective Clothing." Whether or not surgical drapes are to be considered as items of protective clothing is an issue unto itself. However, another question that arises is whether or not the language means that the maximum level of resistance to penetration for a draping material is to be the same as that used in a surgeon's gown, namely, 2 psi. If so, it would appear that an explanation as to how that was determined is in order.
New Questions to be Answered
What seems to have been overlooked are the variances in gowning and draping practices that have accompanied the advances made in surgical techniques since the time those studies were conducted. These may preclude the need for all gowns and drapes to be made of materials that meet the ASTM "pass" requirements. For example:
- With the trend toward small incisions and minimally invasive procedures, how vital is the need for both the gown and drape to be made of what the textile industry considers a "pass" in a material's barrier capability?
- A survey of draping practices found that almost two-thirds of the respondents reported using incise drapes. If an incise drape is used, why is it necessary for the drape to be made of an expensive "barrier" quality material that passes the industry test?
- The latest data released by the American Hospital Association (AHA) in 1997 indicates that 60 percent of the 24 million surgical procedures performed in hospitals were on an out patient basis. Furthermore, it has been estimated that last year, 65 percent of surgical procedures in hospitals were done on an out patient basis and that number is projected to increase another 23 percent in the next five years. Under those circumstances, how vital is the need for both the gowns and drapes to be made of the most costly barrier-quality materials?
- If the drape is to be considered as an item of protective clothing for the patient, why shouldn't its selection be predicated on the same basis as the surgeon's gown (i.e., the level of exposure anticipated)?
- Almost two decades have passed since most of the studies about the influence of barrier-quality materials on SSIs were published. Notwithstanding their shortcomings, other techniques that could influence the outcome of a surgical procedure (i.e., the use of supplemental oxygen) have been made known. This could preclude the need for the drapes to be made of a barrier-quality material.
Nathan L. Belkin, PhD, retired in 1991 following a 40-year career in the healthcare industry. He is the author of more than 100 articles and consulted with a variety of healthcare organizations including APIC and AORN.