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Wound Healing and Antimicrobial Properties of Silver Dressings

Topical antimicrobial dressings are used to prevent and manage infections in a wide range of wounds. Silver, as a topical antimicrobial agent has been used in burns and wound care for hundreds of years. The active agent, silver ions, are effective in killing microbes instantly by blocking the respiratory enzyme system whilst remaining non-toxic to surrounding tissues. Silver is found in dressings in a number of forms:

  • Elemental silver, such as, silver metal, nanocrystalline silver
  • An inorganic compound, such as, silver oxide, silver phosphate, silver chloride, silver sulfate, silver-calcium-sodium phosphate, etc.
  • An organic complex, such as, silver alginate, silver-zinc allantoinate, etc.

 

The silver component of the dressings may appear in the following forms:

 

  • as a coating, on one or both the external surfaces of the dressing (elemental or nanocrystalline silver);
  • within the structure of the dressing, either as a coating on dressing material (elemental or compound silver), within the space of the dressing material (elemental or compound silver) or as a compound that forms a part of the dressing structure (eg. Silver alginate); the Systagenix Actisorb 220 Activated Charcoal Dressing, has silver encased in a nylon sleeve. It not only traps the wound malodor, but also protects the wound against infection.
  • as a combination of these.

     Systagenix Actisorb 220 Activated Charcoal Dressing

Silver on the surface of the dressing comes in direct contact with the wound where its antimicrobial action takes place. Silver within the dressing structure acts on bacteria absorbed into the dressing with the wound exudate, but may get diffused to some extent into the wound.

How does silver work?

Silver, in its elemental form, is non-reactive and cannot kill bacteria. To become bactericidal, elemental silver has to be ionized. This happens when it is exposed to an aqueous environment such as wound exudate. Silver ions are highly reactive and affect multiple sites within bacterial cells, leading to death of bacterial cells. They bind to the bacterial cell membranes causing disruption of the bacterial cell wall, cell leakage and interfering with energy production, enzyme function and cell replication.

Silver ions are active against a wide spectrum of bacteria, fungi and viruses, including many antibiotic-resistant bacteria.

As per various studies conducted, only a small proportion of silver in a dressing is involved in the antimicrobial action. Most of it remain within the dressing or binds itself to the protein in the wound or wound debris. Very little is systemically absorbed, and even if so, it is excreted in faces and urine. It is never absorbed into the nervous system.

When to use silver dressings?

Silver dressings are best for:

  • Acute wounds, such as surgical or traumatic wounds and burns;
  • Chronic wounds, such as diabetic foot ulcers, venous leg ulcers, pressure ulcers, arterial leg/foot ulcers; the Medline SilvaSorb Antimicrobial Wound Gel, is best meant for such conditions. Its properties manage bacterial burden, give prolonged antimicrobial protection, advanced fluid management and extended wear time. At the same time, it is non-staining and gentle for the patient.
  • Systemic infection, involving severe sepsis and multiple organ dysfunction.

In cases of infected acute or chronic wounds obstructed from healing by microorganisms, a silver dressing reduces bioburden.

In cases of acute or chronic wounds at a high risk of infection or re-infection, a silver dressing acts as an antimicrobial barrier.

The Molnlycke Mepilex Ag Absorbent Antimicrobial Foam Dressing with Safetac Technology, best addresses these requirements. It involves antimicrobial action which reduces bioburden in infected acute or chronic wounds. It also acts as an antimicrobial barrier in wounds at a high risk of infection or re-infection. This also contains the foul odor. The Safetac technology minimizes pain and skin damage at dressing changes.

Likewise, the Medline Maxorb Extra Ag Silver Alginate Antimicrobial Flat Rope Wound Dressing, provides antimicrobial protection up to 21 days. The fluid does not wick laterally as the wound exudate mixes with the dressing to form a gel.

  Molnlycke Mepilex Ag Absorbent Antimicrobial Foam Dressing with Safetac Technology   Medline Maxorb Extra Ag Silver Alginate Antimicrobial Flat Rope Wound Dressing

The manufacturer’s instructions relating to wound cleansing and method of application should be clearly followed.

When not to use silver dressings?

Silver dressing should not be used in the following cases:

  • No symptoms of localized, spreading or systemic infection;
  • Surgical/small acute wounds at low risk of infection;
  • Chronic wounds healing as per comorbidities and age;
  • Patients sensitive to silver or any of the dressing components;
  • During pregnancy or lactation; and
  • When contraindicated by the manufacturer

 

Whilst, the merits of using silver in wound management cannot be negated, it is known to have some side effects. These include maceration, irritant, or allergic contact dermatitis. There have been rare instances of acute hemolytic anemia or transient leukopenia and electrolyte imbalance.