Useful Web Sites

www.worldwidewounds.com/index.html (VIN editor: link was modified on 3/29/16)

http://www.dressings.org

A wound dressings is any material which covers and protects a wound to facilitate or enhance wound healing. The function of a dressing is broad and includes wound debridement, facilitating a moist wound environment, facilitating absorption of excess wound fluid, providing analgesia, providing protection against trauma and prevention of infection. Whilst providing these properties the dressing needs to be non-toxic, non-irritant, non-allergic and cost effective.

Moist wound healing is frequently advocated as the ideal approach to wound management. Moist wound healing is achieved by applying a primary dressing to the wound that prevents wound desiccation. The theory of moist wound healing is that wound exudate contains factors (such as growth factors) that promote wound healing and hence by maintaining a moist environment within the wound bed and hence the wound exudate then wound healing will be accelerated.

Unfortunately, there is insufficient evidence to suggest whether the choice of dressing or topical agents affects the healing of wounds by secondary intention and if a factor has an effect on open wound healing, whether positive or negative, that effect is most marked early in the course of healing (10–15 days). After that, differences between treatment and control wounds are negligible. As a consequence the ideal approach to wound dressing choice is to understand the factors affecting wound healing and the properties of each dressing. This allows selection of dressings to address relevant factors that are influencing wound healing. No singular dressing provides all the desired functions for every circumstance. Additionally the dressing requirements change according to the characteristics of the wounds that is being treated.

Prior to selection of wound dressings a wound prognosis should be made. Pressure sores, diabetic ulcers and venous leg ulcers are rare in veterinary patients and wound prognosis is more frequently influenced by the size, extent and location of the wound which could result in failed wound healing with dressing management alone rather than endogenous factors. The wound prognosis should include decision making between wounds that will realistically heal with dressing management and those that need surgical reconstruction. Early identification of wound that require surgical reconstruction avoids prolonged and frequently expensive dressing management that could have been avoid with early surgical intervention. In the uncommon scenario of chronic non-healing wounds, local wound factors, endogenous or patient and exogenous factors should be considered to develop a prognosis.

The selection of wound dressings in human wound management has been facilitated by the development of the TIME or DIME mnemonics which direct the clinical towards dressing selection on the basis of tissue debridement, presence of infection, moisture balance and edge of wound epithelial migration (Table 1). The same approach can be applied to veterinary patients.

Table 1

Wound debridement can be achieved via surgical, autolytic, mechanical, biological and enzymatic degradation. The selection of debridement technique is a balance between efficacy and speed of debridement and selectivity. The method of wound debridement selected is influenced by the presence of vital structures within the wound, the potential for ongoing tissue necrosis and anatomical location of the wound.

Surgical debridement provides the fastest method of removing necrotic tissue; however, due to a limited ability to predict tissue viability and the potential for ongoing tissue necrosis within the wound bed staged debridement can be required. Surgical debridement can be performed as either an en bloc excision or as a layered approach. The presence of vital structures that need to be preserved with the wound bed result in a requirement for a conservative surgical approach and frequently dictates a requirement for the use of other methods.

Autolytic debridement is a highly selective process utilising macrophage and endogenous proteolytic enzymes which liquefy and separate necrotic tissue from healthy tissue. This process is achieved by creating a moist would environment. Hydrophilic dressings with a semi-occlusive backing such as hydrocolloids, hydrogels and calcium alginate dressings all facilitate autolytic debridement.

Mechanical debridement is achieved with wet to dry dressings. Their debridement action is completely physical and requires adherence of the bandage to the wound for effect. Wet-to-dry dressings require intense wound care with daily dressing changes. The extent of debridement afforded is high but is non-selective and removes normal tissue and, hence, should not be utilised in wounds with granulation tissue. Biological debridement is the use of medical grade maggots. Maggots secrete digestive enzymes to dissolve necrotic tissue. Maggot therapy needs to be carefully monitored as only the early lavage stages are selective for necrotic tissue, prolonged application leads to autolysis of healthy tissue as the larvae mature.

Enzymatic debridement is primarily indicated in chronic, non-healing wounds in which surgical debridement is not possible. These agents take time to have an effect, can be expensive, are nonselective and can damage normal tissue and provide inadequate debridement. They are rarely indicated in veterinary patients.

Infected wounds in most circumstances should be managed with systemic administration of antibiotics rather than topical antiseptic/antibiotic solutions. Wounds should be cleansed with low-toxicity solutions (such as normal saline or water). Topical antiseptic solutions should be reserved for wounds that are non-healable or those in which the local bacterial burden is of greater concern than the stimulation of healing.

Moisture balance is achieved by creating a moist wound environment. Application of a hydrophilic dressing with a semi-occlusive backing facilitates moist wound healing. Absorptive capacity varies among dressings; dressing selection is therefore often dictated by the rate of wound exudate production (Table 2).

Dry to minimally exudative wounds can benefit from water-based hydrogel dressing. The gel can be applied to the wound and covered by a semi-occlusive dressing or may be already impregnated into a semi-occlusive dressing. The gel provides exogenous moisture to the wound surface, and its hydrophilic action holds moisture at the wound surface in a thin film.

Mild to moderately exudative wounds can benefit from application of a hydrocolloid sheet, polyurethane foam dressing, or maltodextran polymer flakes. These dressings are dry on contact but are extremely effective hydrophilic agents and form a gelatinous layer at the wound surface.

Heavily exudative wounds can benefit from colloidal dressings containing calcium alginate or hypertonic saline dressings. Alginate is a potent hydrophilic agent derived from seaweed. It is applied in sheets or ropes and held in place by a semiocclusive dressing.

Table 2