DO DIFFERENT WOUND DRESSINGS PROMOTE WOUND HEALING? A MUGANZA MD, FCS (SA), FRCSI Head, Burns Unit, Chris Hani Baragwanath Academic Hospital and University of Witwatersrand Wound healing is a complex and dynamic process, with the wound environment changing with the shifting health of individual. Understanding the physiology of the normal wound healing through the phases of haemostasis, inflammation, granulation and maturation provides the basic principles of wound healing. Through this knowledge a health professional can develop skills required to choose the correct dressing for a particular wound. The choice of dressing requires a holistic, cost effective and evidence-based approach. The properties of the ideal wound dressing to promote wound healing are as follow: Promotes a moist wound environment. Provides mechanical protection. Allows no adherence to the wound. Allows removal without pain or trauma. Capable of absorbing excess exudates. Allows gaseous exchange. Non-cytotoxic to health tissue. Antimicrobial/anti-fungal. Acceptable to the patient. There are more than 3 000 types of wound dressings available on the market today, making it easy to become overwhelmed by options.
The secret to understanding various types of wound dressings is to learn the basic properties of the following eight main categories. Gauze Traditionally, gauze wound dressings were made from woven or non-woven gauze. Gauze dressings continue to be the most readily available wound dressings in use today. Gauze is highly permeable and relatively nonocclusive. Gauze dressings may promote desiccation in wounds with minimal exudate unless used in combination with another dressing or topical agents. Gauze may be used as a primary or secondary wound dressing. Gauze dressings are inexpensive for one-time or short-term use. Gauze dressings come in many forms: squares, sheets, rolls, and packing strips. Films Film dressings are thin, flexible sheets of clear polyurethane combined with an adhesive coating on one side to allow adherence to the skin. The adhesive reacts with wound exudate to prevent adhesion to the wound bed, while allowing the film to stick to the dry skin surrounding the wound. Film dressings are highly elastic and conformable to contours, and are suitable for use either as a primary or secondary dressing. The transparent quality of film dressings allows visualisation of the wound. Hydrogels Hydrogel wound dressings are 80% to 99% water or glycerine-based dressings that are available in sheets, gel, or impregnated gauzes. Hydrogels can only absorb a minimal amount of fluid, but since they have a high water or glycerine content they are able to donate moisture to dry wounds. This property also means they may dehydrate easily, particularly if water based. When applied to the skin or wound, they feel cool and may decrease wound pain. Hydrogels are permeable to gas and water, making them less effective bacterial barriers than semipermeable films or hydrocolloids. Almost all hydrogels are non-adhesive and require a secondary dressing.
Foams Foam wound dressings are sheets and other shapes of foamed polymer solutions (most commonly polyurethane) with small, open cells capable of holding fluids. They may be impregnated or layered in combination with other materials. Absorption capability depends on thickness and composition. The area in contact with the wound surface is non-adhesive for easy removal. They are available with an adhesive border and/or a transparent film coating that acts as a bacterial barrier. These dressings are indicated for partial and full thickness wounds. Alginates Alginate wound dressings are made from brown seaweed. When placed within the wound bed, alginate dressings react with serum and exudate to form a gel. This gel provides a moist wound environment and may trap bacteria, which can then be washed away during dressing changes. It is important not to confuse this with wound infection. Alginates are highly permeable and non-occlusive. Therefore they require a secondary dressing, most commonly gauze. Alginates are available in three forms. Alginate sheets may be placed on wound beds to absorb drainage. Alginate ropes are used to tightly fill wound tunnels or areas of undermining, and alginate-tipped applicators can be used to probe wounds. Hydrofibres These are dressings made from sodium carboxymethycellulose. They are similar to alginates in appearance, use and precautions; and are often used interchangeably with alginates. Composites Composite or combination wound dressings are multi-layer dressings that can be used as primary or secondary wound dressings. Most composite dressings have three layers.
The inner contact layer is non-adherent, preventing trauma to the wound bed during dressing changes. The middle layer absorbs moisture and wicks it away from the wound bed to prevent maceration, while maintaining a moist wound environment. This middle layer may consist of a hydrogel, semipermeable foam hydrocolloid, or alginate. The outer layer serves as an antibacterial barrier, and is commonly composed of a semi-permeable film. Because composite dressings are pre-packaged they have less flexibility in terms of indications for use; and buying and storing these dressings can be quite costly. Hydrocolloids Hydrocolloid wound dressings contain hydrophilic colloidal particles such as gelatine, pectin and cellulose. They have a very strong film or foam adhesive backing. Hydrocolloids absorb exudate slowly by swelling into gel-like mass. Upon removal, a residue commonly remains within the wound bed. Because this residue may have a foul odour, it is often mistaken as a sign of infection. Hydrocolloids come in a variety of sizes and pre-cut shapes. Several hydrocolloids have beveled edges to reduce the tendency for the dressing to roll when placed in high-friction areas. Hydrocolloids provide thermal insulation to the wound and are impermeable to water, oxygen, and bacteria. Wounds dressed with hydrocolloids have lower infection rates than wounds covered with gauze, semi-permeable films, sheet hydrogels, or semipermeable foams. In the last decade two strategies to promote wound healing were extensively studied and become a dressing choice for many wounds: Use of silver dressings. Negative pressure dressings.
SILVER In metallic form, silver is non-reactive and cannot kill bacteria. To become bactericidal, silver atoms must lose an electron and become positively charged silver ions (Ag+). They bind to bacterial cell membranes, causing disruption of the bacterial cell and cell leakage. Silver ions transported into the cell disrupt cell function and cause cell death. Silver ions are active against bacteria, fungi and viruses. Today many of the dressings mentioned above are impregnated with silver. NEGATIVE PRESSURE WOUND DRESSING THERAPY This form of dressing uses a vacuum to promote healing in acute or chronic wounds and enhance healing. The continuous vacuum draws out fluid from the wound and increases blood flow to the area thus promote wound healing. The vacuum can be applied intermittently or continuously. There is some evidence that if negative pressure dressings are correctly used wound healing may be accelerated. SKIN SUBSTITUTES The last innovation to promote wound healing is the use of skin substitutes, particularly for partial thickness burns. Many of them are applied in theatre, however at Chris Hani Baragwanath Academic Hospital we find that most of the skin substitutes can be applied in the ward by nurses on appropriately selected patients. In summary the choice of dressing to promote wound healing must incorporate the following themes: Understanding wound healing pathophysiology. Holistic approach: assessment of the "whole" patient not just a "hole" in the patient. Evidence-based and demonstrated cost-effectiveness.