Silver dressings really shine in wound healing.
"Silver is a very potent antimicrobial. It kills bacteria instantly," said Dr. Demling, professor of surgery at Harvard Medical School and director of education and research at Brigham and Women's Hospital in Boston.
Perhaps more important, bacterial resistance to silver has yet to be noted, he added.
"There is also a direct healing effect from using silver," Dr. Demling said. There are a number of factors that contribute to delayed healing. Open wounds have an increased bacterial load, increased neutrophil count, increased proteolytic activity, and altered growth factor activity.
In particular, burns and chronic wounds have increased levels of metalloproteases, which break down the collagen and growth factors that are necessary for wound healing. Recent studies have shown that silver decreases the activity of metalloproteases. In addition, silver increases surface calcium levels, speeding up reepithelialization.
Although silver compounds have been used for years in wound healing, one of the problems with using silver for wound care has been that silver crystal is very water insoluble.
Thanks to nanotechnology, however, silver crystals can be made more water reactive, which in turn means that higher amounts of pure silver will be released directly into a wound when the metal is used in dressings.
The advantage of this method of release is that silver alone is not toxic to human tissue, whereas some of the compounds to which silver is typically bound--silver sulfadiazine, silver nitrate--are, Dr. Demling said.
Silver's anti-inflammatory properties are another attractive reason for using silver dressings. "Silver decreases excess inflammation in chronic wounds and burns. It does so in one way by decreasing excess protease activity on the wound surface," he explained.
Silver dressings also maintain wound moisture, which is critical for healing, while minimizing exudate. Less exudate means that the dressing has to be changed only about once every 4 days, which decreases mechanical trauma to the wound, he noted.
Acticoat, a commonly used silver dressing, is composed of two controlled-release nanocrystalline silver meshes enclosing a rayon core. Moisture from the wound releases the silver from the mesh, a process that can last up to 7 days.
Although silver dressings are more costly than conventional dressings, several studies have shown that the savings in nursing time associated with dressing changes make up for the increased cost of the dressing, Dr. Demling said.
BY KERRI WACHTER
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|Title Annotation:||Infectious Diseases|
|Publication:||Internal Medicine News|
|Date:||Oct 15, 2004|
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