Questioning The Evidence Behind The Use Of Silver Dressings
A few months ago, Robert Kirsner, MD, PhD, and Stephanie Wu, DPM, invited me to write a chapter on “Antimicrobial Therapy” in their upcoming Wound Healing Society Yearbook. The design of the chapter is a review of a recently published primary study and two or more secondary studies.
I was extremely familiar with the primary study, the randomized controlled trial on pexiganan (Dipexium) versus ofloxacin (Floxin®, Daiichi-Sankyo) by Lipsky and colleagues.1 However, one of the secondary studies really struck a chord with me. It was the study in the British Journal of Surgery by Michaels and colleagues, who reported on the VULCAN trial, a large randomized trial looking at the use of silver dressings in venous leg ulcerations (VLU).2
This study of 213 recruited patients not only looked at wound healing differences between silver-containing dressings and non-silver, low adherence dressings in the treatment of VLU but also the cost effectiveness of the two.2 The primary measure was complete ulcer healing at 12 weeks with secondary measures including: time to healing, quality of life and the aforementioned cost effectiveness. Although I do have some issues with the study design including the leeway given in dressing selection, compression definition and number of visits, I do find the results interesting.
As one might reasonably expect given the paucity of good evidence on the effectiveness of silver dressings as a class, the VULCAN study found no significant differences between dressings in the number of ulcers healed at 12 weeks (59.6 percent in silver dressings, 56.7 percent in non-sliver dressings) and no differences in median time to healing.2 As one may also expect, silver dressings cost significantly more to use ($46.60 vs. $8.70 as converted from the reported British pounds). As the authors concluded, “There was no evidence to support the routine use of silver-donating dressings beneath compression for venous ulcerations.”
This finding won’t surprise anyone who has heard me lecture on “Differentiating Infected From Non-Infected Wounds” as I did at the recent American Podiatric Medical Association (APMA) meeting in Seattle. It should also not surprise those who have read the chapter on “Diabetic Foot Infections” in the 3rd Edition of the Handbook of Lower Extremity Infections (specifically page 120).3 The finding also will not surprise anyone who has read my blog post from March 3, 2010 entitled “Bioburden and Wound Healing.” (See the third blog down at www.leinfections.com/2010/03/ )
Silver dressings are everywhere. Just about every wound healing product line includes a number of silver donating products in every imaginable format. Yet there is little to no evidence to support that they have any benefit in wound healing or preventing wound infection.
This revelation first came to me upon reading the Cochrane Collaborative systematic review of the literature on silver dressings that, like the VULCAN trial, found little evidence to support their routine use.4 This does not mean I do not use silver dressings. Like most clinicians, if I see a heavily colonized wound, I am seemingly genetically programmed to reduce the bioburden and kill the bugs.
What I am saying is that we should be practicing evidenced-based medicine and not costing our patients or the healthcare system dollars that none of us can afford to spend on a therapy without solid science behind it.
So the next time a sales rep comes to speak to you about the latest and greatest silver product, ask for scientific proof that it contributes to wound healing rather than some pretty “before and after” pictures. Unfortunately, I doubt you will get much. These products all have FDA approval as 510k medical devices. Therefore, there is little clinical science necessary to get them approved.
1. Lipsky BA, Holroyd KJ, Zasloff M. Topical versus systemic antimicrobial therapy for treating mildly infected diabetic foot ulcers: a randomized, controlled, double-blinded, multicenter trial of pexiganan cream. Clin Infect Dis. 2008; 47(12):1537-45.
2. Michaels JA, Campbell B, King B, Palfreyman SJ, Shackley P, Stevenson M. Randomized controlled trial and cost-effectiveness analysis of silver-donating antimicrobial dressings for venous leg ulcers (VULCAN trial). Br J Surg. 2009; 96(10):1147-56.
3. Joseph WS. Diabetic Foot Infections. In Joseph WS (ed.): Handbook of Lower Extremity Infections, third edition. Data Trace, Brooklandville, MD. Chapter 5, p. 120.
4. Vermeulen H, van Hattem JM, Storm-Versloot MN, Ubbink DT. Topical silver for treating infected wounds. Cochrane Database Syst Rev 2007 Jan 24;(1):CD005486
Editor’s note: This blog originally appeared at www.leinfections.com/ and has been adapted with permission from Warren Joseph, DPM, FIDSA, and Data Trace Publishing Company. For more information about the Handbook of Lower Extremity Infections, visit www.leinfections.com/ .