Topical silver for infected wounds

Vermeulen H, van Hattem JM, Storm-Versloot MN, Ubbink DT. Topical silver for treating infected wounds. Cochrane Database Syst Rev. 2007(1);CD005486.

What is the clinical evidence base for silver dressings in the management of contaminated and infected acute and chronic wounds?

Investigations were identified by Cochrane Wounds Group Specialized Register (2006), CENTRAL (2006), MEDLINE (2002-2006), EMBASE (2002-2006), CINAHL (2002-2006), and digital dissertations (2006) searches. Product manufacturers were contacted to identify additional eligible studies. The search terms included wound infection, surgical wound infection, ulcer, wound healing, and silver.

Each study fulfilled the following criteria: (1) The study was a randomized controlled trial of human participants that compared dressings containing silver with any dressings without silver, dressings with other antiseptics, or dressings with different dosages of silver. (2) The participants were aged 18 years and older with contaminated and infected open wounds of any cause. (3) The study had to evaluate the effectiveness of the dressings using an objective measure of healing. No language or publication status restrictions were imposed, and participants could be recruited in any care setting. Studies were excluded if the wounds were ostomies (surgically formed passages).

Study quality assessment was conducted independently by 3 authors using the Dutch Institute for Health Care Improvement and Dutch Cochrane Centre protocols. Characteristics of the study, participants, interventions, and outcome measures were extracted by one author and verified by a second using a standard form. The principal outcome measure was healing (time to complete healing, rate of change in wound area and volume, number and proportion of wounds healed within trial period). Secondary measures were adverse events (eg, pain, maceration, erythema), dressing leakage, and wound odor. Based on the unique comparisons in the studies, a meta-analysis was not conducted. As a result, summary estimates of treatment effect were calculated for each outcome comparison. RevMan software (version 4.2; Cochrane Centre, Oxford, United Kingdom) was used for statistical analysis.

Specific search criteria identified 31 studies for review, of which 3 met the inclusion and exclusion criteria. Lack of randomization and absence of wound infections excluded the majority of studies from the review. In the 3 studies selected, silver-containing dressings were compared with nonsilver dressings and dressings with other antimicrobials. One group used a silver-containing foam dressing and a nonsilver foam dressing; another group used a silver-containing alginate and a nonsilver alginate; and a third group used a silver-containing foam and various dressings (nonsilver foams, alginates, hydrocolloids, and gauze and other antimicrobial dressings). Sample sizes ranged between 99 and 619 participants. Most of the wounds in the included studies were pressure, diabetic, and venous leg ulcers. Wound infection was subjectively defined by 1 group as the presence of 2 or more signs and symptoms (eg, continuous pain, erythema, heat, or moderate to high levels of exudate) and by the other 2 groups as signs of critical colonization (eg, delayed healing, increased pain and exudate levels, discoloration, and odor). The primary measure in the included studies was healing outcome. The 3 groups used various assessments of healing, including relative and absolute reduction in wound area and number of wounds healed during the trial period. The trial period in each study was 4 weeks. In the 3 trials, the authors randomized the participants to the treatment groups. Examining healing, one group (129 participants) compared Contreet silver foam (Coloplast A/S, Humlebaek, Denmark) with Allevyn foam (Smith & Nephew, St-Laurent, Quebec, Canada). The authors reported no differences for rates of complete healing (risk difference [RD] = 0.00, 95% confidence interval [CI] = -0.09, 0.09) and median wound area reduction (weighted mean difference [WMD] = -0.30 cm(2), 95% CI = -2.92, 2.35). However, Contreet was favored over Allevyn (P = .034) for median relative reduction in wound area (WMD = -15.70 cm(2), 95% CI = -29.5, -1.90). One group (99 participants) compared Silvercel silver alginate (Johnson & Johnson Wound Management, Somerville, NJ) with Algosteril alginate (Johnson & Johnson Wound Management). The authors found no differences in rates of complete healing (RD = 0.00, 95% CI = -0.06, 0.05), mean absolute (WMD = 4.50 cm(2), 95% CI = -0.93, 9.93) and relative wound area reduction (WMD = -0.30 cm(2), 95% CI = -17.08, 16.48), or healing rate per day (week 1 to 4) (WMD = 0.16 cm(2), 95% CI = -0.03, 0.35). One group (619 participants) compared Contreet with various dressings (nonsilver foams, alginates, hydrocolloids, and gauze and other antimicrobial dressings). For median relative wound area reduction, the authors noted a superiority of Contreet over the various dressings (P = .0019). Examining secondary outcomes, 2 groups used subjective analysis to compare adverse reactions among the dressings. One group reported no difference between Contreet (in satellite ulcers, deterioration of periwound tissue) and Allevyn (in satellite ulcers, maceration, eczema) (RD = 0.02, 95% CI = -0.07, 0.12), and one group found no difference between Silvercel (in pain during dressing change, eczema, periwound erythema, maceration) and Algosteril (in pain during dressing change, eczema, erythema) (RD = -0.01, 95% CI = -0.12, 0.11). Two groups subjectively assessed leakage among silver and nonsilver dressings. The data from one group demonstrated superiority of Contreet over Allevyn (P = .002; RD = -0.30, 95% CI = -0.47, -0.13), and one group found Contreet better than various dressings (eg, nonsilver foams, alginates, hydrocolloids, and gauze, and other antimicrobial dressings) (P = .0005; RD = -0.11, 95% CI = -0.18, -0.05). Using a subjective 4-point scale, one group compared silver and nonsilver dressings and reported a difference favoring Contreet over Allevyn in terms of wound odor (P = .030; RD = -0.19, 95% CI = -0.36, -0.03).

Overall, this review provides no clear evidence to support the use of silver-containing foam and alginate dressings in the management of infected chronic wounds for up to 4 weeks. However, the use of silver foam dressings resulted in a greater reduction in wound size and more effective control of leakage and odor than did use of nonsilver dressings. Randomized controlled trials using standardized outcome measures and longer follow-up periods are needed to determine the most appropriate dressing for contaminated and infected acute and chronic wounds.