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Silver For Treating Wounds

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Silver For Treating Wounds

Silver For Treating Wounds

November 26, 2007

By: Norman Bauman for Veins1

There are new methods for treating leg ulcers. Are they better than the old methods? And since they can be more expensive, are they worth it?

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  • Antibiotics alone may not heal leg ulcers.
  • Elastic bandages are very effective in healing leg ulcers.
  • The only way to know for sure that a treatment works is with large randomized, controlled trials.
  • Some doctors have good results with silver-covered bandages, some doctors don't, and there are still no good randomized, controlled trials to show that they work.
  • You can find out if there is strong scientific evidence for a treatment at http://www.cochrane.org and (for wounds) at http://www.woundheal.org
  • That was the debate at the VEITHsymposium™ on vascular surgery in New York. Does modern wound care contribute to the cost explosion? Robert E. Burrell, Ph.D., chair of the biomedical engineering department of the University of Alberta, Edmonton, Canada, gave an example. A 21-year-old man with badly-controlled type I diabetes was admitted to the University of Toronto hospital. Among other things, he had three wounds on his shin, of up to three by three centimeters, or about the size of a watch. He had been using an antibiotic cream for eight months, and his doctor had told him that because he was diabetic, the wounds would never heal and he would likely lose his leg.

    The hospital team took bacterial cultures, and used nanocrystalline silver dressings on the wounds to control the bacteria. They recognized that his leg was swollen with fluid, so they wrapped the leg with elastic bandages to control the fluid. Three weeks later, the wounds had closed. His leg had blood circulation and pulses, so there was no reason to amputate.

    Nanocrystalline silver bandages are more expensive – $13 (Canadian) per bandage – but they worked. Old-style care took eight months and left him with a non-healing wound. New-style care took three weeks and left him with a healed wound. The silver bandages were actually cheaper than the $600 spent on gauze bandages and antibiotics over eight months. But the cost of bandages is negligible, said Dr. Burrell, compared to the cost of nursing care. In some studies "the least expensive product to purchase was the most costly to use." According to published calculations by Laura M. Teague, R.N. and James L. Mahoney, M.D., in Toronto, the cost of nursing for the old treatment over eight months was $9,600; the cost of nursing for the new treatment over three weeks was $240. Total cost for the old treatment was $10,248; total cost for the new treatment was $534.50. (Cost-effective Wound Care: How the Advanced Practice Nursing Role Can Positively Affect Outcomes in an Acute-care Setting, Wound Care Canada 2(1):32.) And in addition to the dollar value, said Dr. Burrell, the cost to the patient was very high as he suffered from non-healing wounds for eight months.

    What's the evidence?

    Not so fast, said Michael S. Weingarten, M.D., chief of vascular surgery at Hahnemann University Hospital, Philadelphia, Pennsylvania. The argument is that new technologies save money in the long run because they heal wounds faster and reduce the number of treatments. But in fact the cost of treating wounds has "increased dramatically" in the last few years. One example, or a few examples, isn't enough. The claims of effectiveness are "often based on anecdotal studies or small randomized controlled trials." Many of these studies are supported by industry, which raises concerns about bias. "Aggressive marketing" has also led to indiscriminate use of high-tech products as a substitute for good wound care.

    One of the generally-recognized standards for medical evidence is the Cochrane Collaboration, which reviews and evaluates all the studies in the medical literature on particular treatments, and makes their summaries available free on the Internet. In 2007, the Cochrane Wounds Group found three good studies on silver dressings. They found that "silver-containing foam dressings did not result in faster wound healing after up to four weeks of follow-up. One study did find that the overall size of the ulcer reduced more quickly when dressed with a silver-containing foam." They concluded, "There is not enough evidence to recommend the use of silver-containing dressings or topical agents for treating infected or contaminated chronic wounds." (Topical silver for treating infected wounds. Cochrane Database of Systematic Reviews 2007, Issue 1. Art. No.: CD005486.)

    Is nanocrystalline silver better?

    Dr. Burrell and Liza G. Ovington, Ph.D., Associate Medical Director at Johnson & Johnson Wound Management, Sommerville, New Jersey, explained the technical aspects of silver. Silver nitrate (which has been used since 1887), silver sulfadizine, and other silver salts are topical drugs for infection control. Dressings incorporate silver and deliver it in many ways and at different rates, said Dr. Ovington, but the active ingredient they all deliver is the positively-charged silver ion. Clinical studies have found silver dressings to be beneficial, but comparisons among silver dressings have not been done.

    Even so, Dr. Burrell believed that nanocrystalline-derived silver provides the broadest spectrum of activity and the fastest rate of kill. Bacteria from wounds and ulcers form biofilms, which are yogurt-like coatings that protect the bacteria from antibiotics, said J. Barry Wright, Ph.D., Principal Research Scientist at GlaxoSmithKline, Collegeville, Pennsylvania. He described laboratory experiments at the University of Calgary, Canada, in which silver salts could kill normal bacteria, but couldn't kill the same bacteria in biofilms. However, bandages covered with nanocrystalline silver could kill the bacteria in biofilms. This was confirmed in animal experiments with pigs, but not yet with humans. So nanocrystalline silver may be effective at killing bacteria in biofilms, but we need more research to be sure, said Dr. Wright.

    Silver-resistant bacteria

    One of the problems that doctors fear is methicillin-resistant Staphylococcus aureus (MSRA), a common infectious bacterium which has become resistant to penicillin-type antibiotics because of antibiotic over-use. Silver dressings might be effective against MRSA, said Robert Strohal, M.D., head of the dermatology department at the Federal University Teaching Hospital of Feldkirch, Austria. To find out, his group tested different silver-impregnated bandages by placing them on agar plates saturated with MRSA. The nanocrystalline silver dressings worked best. After the laboratory studies, they did a small clinical study with seven patients who had actual MRSA-infected wounds. The nanocrystalline silver dressings did reduce the MRSA load and sometimes eliminated it. Equally important, the MRSA didn't leak through the bandages to the outer surface, and this would help prevent the spread of MRSA in hospitals. This area also needs more research, and they have started a large clinical trial in Europe to confirm these results.

    If bacteria can become resistant to methicillin, can they also become resistant to silver? Several silver-resistant bacteria have been found, and the silver-resistance genes have been identified and sequenced, said Steven Percival, Ph.D., ConvaTec Wound Therapeutics, Flintshire, UK. He took 110 samples of bacteria from diabetic foot ulcers and screened them to find 12 samples with the silver-resistance genes. They inoculated the bacteria in agar plates, with silver bandages, and the silver killed the bacteria even though they had silver-resistance genes. The bacteria with silver-resistance genes were Enterobacter cloacae, an intestinal bacterium which is usually not a pathogen in wounds. The bacteria which are pathogens in wounds, Staphylococcus aureus and Pseudomonas aeruginosa, didn't have silver resistance genes.

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  • Thursday15, Nov 15 2007 16:38 EST by peterpan56

    Thanks for the helpful information. Here is a picture of and aortic aneurism that may help explain the condition. http://health-pictures.com/conditions1/abdominal-aneurism-aortic-picture.htm

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