Silver Dressings For

DIABETIC MICROVASCULAR COMPLICATIONS

Silver Dressings for Diabetic Foot Ulcers Silver dressings are an important adjunct to good wound care to improve the wound environment and to facilitate healing. BY EDWARD B. JUDE, MD, MRCP

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nfection is a major impediment to healing of diabetic foot ulcers. Before wounds become infected, most are colonized. When the wound burden increases to >105 organisms, it is said to be critically colonized and clinical infection can then occur.1 In more virulent organisms, however, this critical wound burden is not always crucial. Optimal management of the wound bacterial load is important in achieving healing of diabetic foot ulcers. Most often, antibiotics are necessary to treat infection and reduce the bacterial load on the wound. Dressings also play an important role in managing diabetic foot ulcers. Using antimicrobials can reduce the number of organisms in the wound and therefore not only treat the infection but also prevent colonized wounds from becoming critically colonized. TOPICAL ANTIMICROBIAL AGENTS Various topical antimicrobials, antiseptics, and antibiotics have been used in treating diabetic foot ulcer infection.2 Topical antibiotics such as neomycin, bacitracin, polymyxin B, gentamycin, fusidic acid, mupirocin, and topical antiseptics including hexachlorophene, povidone iodine, and chlorhexidine have been tried in various settings. Although these have their advantages, topical antibiotics have not been very popular. Iodine is probably one of the most common topical antiseptics used in infected foot ulcers. Although antiseptics and antibiotics are widely used, there is insufficient evidence for their use in diabetic foot ulcers.2 SILVER A S AN ANTIMICROBIAL Silver has been shown to have bactericidal properties and has been used in wounds as an antimicrobial for more than a century. It acts by impairing the bacterial electron transport system and some of its DNA function. It kills the microbes on contact through multiple mechanisms of action, such as inhibiting cellular respiration, denaturing nucleic acids, and altering cellular membrane permeability. 18 I REVIEW OF ENDOCRINOLOGY I JULY/AUGUST 2007

For this to happen, silver has to be bioavailable and should be in the ionic form. In the past, silver nitrate (0.5% or 3,176 mg/L) and silver sulfadiazine (1%) were the primary sources of silver. In the last few years, a number of silver-containing dressings have been developed. Silver ions (ionic silver, nanocrystalline silver) have been incorporated in hydrofiber, foam, hydrocolloid, and alginate dressings,3 and have been used to treat acute and chronic wounds.4 FEW STUDIE S AVAIL ABLE Very few studies have been published regarding the use of silver-containing dressings in the treatment of diabetic foot ulcers. In a small study of 27 patients, the healing of diabetic foot ulcers using Contreet foam, silver-releasing foam dressing, (Coloplast; Humlebaek, Denmark) was investigated. In this open-label study of the 18 patients who completed it, four healed (22.2%) in the 4-week treatment period with reduced infection in the ulcer and with good exudate management.5 There was a 56% reduction in ulcer area during follow-up. A progressive decrease in incidence and severity of maceration from the first week of treatment with the overall incidence declining from 52.8% to 30% was observed. In the first randomized controlled trial of silver dressings in diabetic foot ulcers, 134 patients with neuropathic foot ulcers were randomly assigned to either Aquacel Ag (AQAg; ConvaTec, Chester, UK) or Algosteril calcium alginate (CA) (Smith & Nephew, Hull, UK) dressings and secondary foam dressings.6 Patients were treated for 8 weeks or until healing, whichever occurred first. The mean time to healing was 53 days in the AQAg-treated ulcers and 58 days for the CAtreated ulcers (P=.34). Ulcers treated with AQAg, however, showed greater depth reduction than CA-treated ulcers (P=.04). Greater improvement in the ulcer was seen in the AQAg group. Patients were also stratified according to those requiring antibiotic treatment (ie, clinically infected ulcers), and patients treated with AQAg primary dressing showed improved healing and more overall ulcer improvement with less deterioration in the ulcer (P=.02).

Reviewofendo.com SILVER DRE SSINGS IN CLINIC AL PR ACTICE All silver dressings have, in addition to the bactericidal silver properties, the important function of the dressing itself. The selection of a dressing will depend on the condition of the ulcer. Most diabetic foot ulcers produce copious amount of exudate. The primary dressing therefore should be either foam-based or hydrofiber, both of which will absorb the exudate. One advantage with the hydrofiber dressing is its ability to hold wound exudate and microorganisms within its fibers where bacteria are then killed by the ionic silver.7-9 Diabetic foot ulcers generally have multiple organisms isolated from within the wound and methicillin-resistant Staphylococcus aureus (MRSA) is an important infecting organism that can delay wound healing. Silver has bactericidal action against a number of microorganisms.10,11 The efficacy has been demonstrated in laboratory studies against S. aureus, MRSA, vancomycin-resistant enterococci, and a number of gram-negative and anaerobic organisms.12 Therefore, it seems logical to use silver-based dressings in wounds that are clinically infected or at risk of infection. It could be hypothesized from the study described6 that systemic antibiotics and topical silver act in synergy with each other. The added advantage of a hydrofiber dressing in exudating wounds has been proven. Hence, to improve outcomes in infected diabetic foot ulcers and ulcers that are colonized, one should consider silver dressings as an important adjunct to good wound care to improve its environment and to facilitate healing. ■ Edward B. Jude, MD, MRCP, is a Consultant Physician and Honorary Senior Lecturer at Tameside General Hospital, Ashton-under-Lyne, UK. He is also a member of the Institute of Health Sciences Diabetes and Obesity Research Network. He may be reached at [email protected]. 1. Robson MC. Wound infection. A failure of wound healing caused by an imbalance of bacteria. Surg Clin N Am. 1997;77:637-650. 2. Mason J, O’Keeffe C, Hutchinson A, et al. A systematic review of foot ulcer in patients with Type 2 diabetes mellitus. II: treatment. Diabet Med. 1999;16:889-909. 3. Bergin SM, Wraight P. Silver-based wound dressings and topical agents for treating diabetic foot ulcers. Cochrane Database Syst Rev. 2006;1(CD005082).2. 4. White RJ, Cutting K, Kingsley A. Topical antimicrobials in the control of wound bioburden. Ostomy Wound Manage. 2006;52:26-58. 5. Rayman G, Rayman A, Baker NR, et al. Sustained silver-releasing dressing in the treatment of diabetic foot ulcers. Br J Nurs. 2005;14:109-114. 6. Jude EB, Apelqvist J, Spraul M, Martini J and the Silver Dressing Study Group. Prospective randomized controlled study of hydrofiber dressing containing ionic silver or calcium alginate dressings in nonischaemic diabetic foot ulcers. Diabet Med. 2007;24:280-288. 7. Newman GR, Walker M, Hobot JA, Bowler PG. Visualisation of bacterial sequestration and bactericidal activity within hydrating hydrofiber wound dressings. Biomaterials. 2006;27:1129-1139. 8. Bowler PG, Jones SA, Davies BJ, Coyne E. Infection control properties of some wound dressings. J Wound Care. 1999;8:499-502. 9. Piagessi A, Vaccetti F, Rizzo L, et al. Sodium carboxy-methyl-cellulose dressings in the management of deep ulcerations of diabetic foot. Diabet Med. 2001;18:320-324. 10. Jude EB, Unsworth PF. Optimal Treatment of Infected Diabetic Foot Ulcers. Drugs Aging. 2004;21:833-850. 11. Tentolouris N, Jude E B, Smirnof I, et al. Methicillin-resistant Staphylococcus aureus: Increasing problem in a diabetic foot clinic. Diabet Med. 1999;16:767-771. 12. Jones SA, Bowler PG, Walker M, Parsons D. Controlling wound bioburden with a novel silver-containing hydrofiber dressing. Wound Rep Reg. 2004;12:288-294.

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