ear Readers: Silver compounds have been a mainstay of burn care since Charles Fox, MD, established the safety and efficacy of topical silver sulfadiazine 1% cream nearly a half century ago. New silver compounds and delivery systems have the potential to improve wound care outcomes. However, little evidence is available to clinicians about the safety and efficacy of many of the recently developed topical silver products. This month’s Evidence Corner reviews 2 recent articles that summarize available literature on safety and efficacy of topically delivered silver compounds. The first article, by Dr. AB Lansdown, Fellow of the Royal College of Pathologists, provides valuable perspective about silver safety in wound care. His companion article1 describing effects on wound healing is equally informative. More evidence on the safety and efficacy of silver products for topical wound care is provided by the second article reviewed here, including a table of evidence that can serve as a resource for wound care professionals when making decisions regarding the use of topical silver products.
How Safe is Silver in Wound Care?
Reference: Lansdown AB, Williams A. How safe is silver in wound care? J Wound Care. 2004;13(4):131–136.
Rationale: As new, efficacious silver-containing antibacterial wound dressings become available, it becomes increasingly important to examine their risks and benefits.
Objective: The objective of this study was to review available literature on silver chemistry, percutaneous absorption, cutaneous and systemic distribution, and toxicity in patients receiving wound care with silver-containing products.
Methods: The authors summarize knowledge of silver safety and toxicity based on the dermatology, pathology, and toxicology literature.
Results: Silver in wound care products occurs as elemental silver in the form of nanocrystals or foil, inorganic compounds or complexes (eg, silver nitrate, silver sulphadiazine, silver oxide), or organic complexes (eg, colloidal silver or silver-zinc allantoinate). Silver is released in its active form as silver ions, most likely Ag+. Ionic silver can be toxic only if absorbed through the skin, where it has an estimated half-life of 10 to 12 hours, and up to 45% of it bonds to local proteins. Silver absorption is increased through wounded skin, increasing more with depth and extent of the wound, frequency and method of application, silver content of the topical product, and amount of exudate, which interacts with topical products to release ionic silver. Excess silver accumulation in the skin, called argyria, is the most common cutaneous side effect associated with use of silver nitrate, silver sulphadiazine, or dressings containing nanocrystalline silver. This may be accompanied by stinging or burning or a skin rash. Following systemic absorption, silver passes through the liver, kidney, blood, bone marrow, and neurologic tissue, and most of it is excreted through the urine, feces, or skin. Most of these findings are based on studies of wound exposure to silver nitrate or silver sulphadiazine.
Conclusion: Well-designed, controlled clinical investigations with proper ethical approval are needed to balance the relative risks and benefits of the new, efficacious silver-release products.
How Does Silver Help Manage Critically Colonized Wounds?
Reference: Hermans MH, Bolton LL. How do we manage critically colonized wounds? Rehabil Nurs. 2004;29(6):187–194.
Rationale: Diagnosis and management of critically colonized wounds offer special challenges for healthcare professionals. Silver products have been designed to reduce the risk of critical colonization.
Objective: The objective of this study was to summarize evidence of safety and efficacy of silver wound care products and illustrate their use in management of an individual with a diabetic foot ulcer exhibiting symptoms of critical colonization, ie, heavy serous exudate and bright red, easily disrupted granulation tissue that bleeds during dressing changes.
Methods: Authors searched the National Library of Medicine’s MEDLINE© publications database for evidence supporting safety or efficacy of silver dressings in English-language articles addressing “silver wound dressing” as well as individual dressing names.
Results: Wide variability was found in dressing silver content and delivery, testing methods, and quality of clinical and preclinical results supporting the safety and efficacy of topical silver wound dressings. The dressings with the most evidence of safety and efficacy were barrier foam and Hydrofiber® dressings (ER Squibb & Sons, LLC, Princeton, NJ). Many silver dressings lacked evidence of either safety or efficacy. Testing methods remain to be validated clinically. For example, testing a silver dressing in water lacks clinical relevance due to the inactivation of silver by proteins in wound fluid. To address the patient’s needs in the clinical setting, a Hydrofiber dressing that releases ionic silver is selected to manage excess exudate while releasing ionic silver in the dressing and at the wound interface for up to 7 days in amounts sufficient to kill a broad spectrum of pathogenic organisms. Managing chronic wounds requires a holistic approach to address both the patient’s and the wound’s needs. To optimize results, any dressing selected should be applied within a protocol of care that addresses potential causes of tissue breakdown, such as glycemic control and offloading for diabetic foot ulcers, pressure relief for pressure ulcers, or sustained graduated compression to aid venous return for ulcers caused by venous insufficiency.
Conclusions: For critically colonized wounds, topical silver products offer the possibility of tipping the microbial balance2 toward healing, particularly when used in protocols of care that address the wound etiology.
Clinical Perspective
Some topical silver products appear safe and may be efficacious in limiting critical colonization of wounds. However, many of these products lack sufficient evidence of safety and/or efficacy to support their use in wound care. The amount and type of silver in a specific dressing is not adequate information on which to base conclusions of its safety or efficacy. Moreover, any topical dressing selected to address a critically colonized wound should be applied within a protocol of patient and wound care that alleviates all potential causes of tissue deterioration.
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