Key Considerations For Utilizing Silver Dressings
Given the increasing prevalence of antimicrobial resistance, there is a growing interest in emerging wound care products that contain silver. Topical silver has a broad range of antimicrobial activity and has been used extensively to help treat high-risk burn patients. Research has confirmed that silver is effective against gram negative and positive bacteria, methicillin resistant Staph aureus (MRSA), yeast, filamentous fungi and viruses (including varicella zoster and herpes simplex types I and II).1-4 Interestingly, the use of silver for medicinal purposes has been documented back to the time of the Roman empire.5 However, it was not until the late 1800s that silver was documented as being bactericidal. In 1881, Carl Crede, MD, pioneered the installation of dilute silver nitrate in the eyes of neonates to prevent gonorrheal ophthalmia. In fact, the technique still has use today.4,5 William Halstead, MD, a founding father of modern surgery, promoted the use of silver foil dressings for wounds.5 Clinicians used these types of dressings at length until after World War II and they were listed in the Physician’s Desk Reference until 1955. As late as the 1970s, Becker, Marino and Spadaro of the Syracuse, N.Y. Veterans Affairs Hospital, performed studies on the treatment of bone infections with silver-coated fabrics.5 A Closer Look At The Impact And Re-Emergence Of Silver In Wound Care Silver (Ag) is the 47th element in the periodic table of elements. In order for silver to have antimicrobial properties, it must be in its cation form, Ag+. This cation has the ability to bind at multiple sites on bacterial cells (such as bacterial DNA, bacterial enzymes and to proteins in the cell wall), causing cell death and destruction. The silver cation will bind to thiol groups containing sulfur and hydrogen on important proteins that play structural and functional roles to the bacterial cell.2 The medical industry is capitalizing on the healing potential of silver and has been actively developing new products containing silver. There seems to be a new silver containing wound product or dressing every day. Silver is being incorporated into wound vacuum sponges, various topical formulations and a wide array of wound care products. Certainly, clinicians can utilize these new products to help heal difficult wounds. However, questions abound about which product is best, how much silver is needed and when one should use a silver-containing product. Common delivery vehicles include foams, alginates, films, sheets and hydrocolloids. There are also a number of available technologies that release various concentrations of silver cations to wounds. These technologies include silver salts, absorbed or trapped ionic silver in silver charcoal metallic silver products, and nanocrystalline silver coatings that use silver vapor sprayed onto the backings of dressing materials.1 What The Research Says About The Efficacy Of Silver In deciding what specific topical silver to use in a particular clinical situation, one has to identify the differences in rate, amount and delivery of the silver cation to the wound bed. Unfortunately, most of the current literature demonstrates only the in vitro comparisons of silver dressings to specific organisms as opposed to comparisons in actual in vivo environments.2,4,6 Thomas and McCubbin compared antimicrobial effects of four silver-containing dressings on three organisms.4 In this study, they found Acticoat (Smith & Nephew) has a much more rapid onset of action and better performance than the other three products.4 Most of the other products tested still had antimicrobial effects. However, they did not have as a rapid of an effect as Acticoat. Another study by Ovington examined the rate of silver cation release and whether a faster rate was more clinically significant than a slower rate of cation release.2 Of all the dressings tested, each achieved the same reduction in bacterial counts within two hours. This is still less than the typical timeframe between dressing changes.2 Other studies have discussed the amount of silver in dressings and whether too much silver in the wound bed would be harmful to wound healing. It seems that the amount of silver in a particular product is not as important as the amount and rate of silver cations released to the wound bed.