Wound Bandages and Dressings for Animals
The goals of bandaging include:
When constructing bandages, several principles must be followed to avoid complications. The bandages should be sufficiently padded, applied evenly and snugly, composed of three layers (primary, secondary, and tertiary), and placed to avoid traumatizing the newly formed granulation tissue or epithelium.
The first or primary layer directly contacts the wound to allow tissue fluid to pass through to the secondary layer. The first layer may be an adherent or nonadherent dressing. A nonadherent dressing is usually a fine mesh or foam, nonstick material. This layer prevents tissue desiccation and causes minimal trauma. An adherent bandage uses a wide mesh material that allows tissue and debris to become incorporated into the bandage. This debris is then removed with the bandage change. However, because they are nonselective, healthy tissue may also be damaged.
Adherent bandages are classified as dry to dry, wet to dry, or wet to wet based on the composition of the primary layer. Dry-to-dry bandages consist of dry gauze applied to the wound. The bandages are painful to remove but enable significant tissue debridement. Wet-to-dry bandages are made with saline-moistened gauze placed directly on the wound. They are also painful to remove but result in less tissue desiccation than dry-to-dry bandages. Wet-to-wet bandages tend to damage the tissue bed by keeping it too moist.
The secondary layer of a bandage absorbs tissue fluid, pads the wound, and supports or immobilizes the limb. This layer is typically composed of cast padding or roll cotton.
The tertiary layer functions to hold the primary and secondary layers in place, provide pressure, and keep the inner layers protected from the environment. This layer is composed of adhesive tape or elastic wraps.
Bandages have a number of potential complications. Bandages applied too tight can result in neurovascular compromise and subsequent tissue necrosis. In some cases this damage can result in loss of a limb.
Bandages are used to help keep wounds moist for optimal healing. This can also result in excess moisture left in contact with healthy skin. The enzymes in wound exudate can cause moisture-associated skin damage (MASD) in healthy skin. MASD may also be induced by retention of urine or fecal matter within the bandage. Commercial barrier creams are available to protect healthy skin from MASD.
Dressings are designed to aid in wound healing.
The ideal dressing should:
It may also aid in debridement, absorb exudate, or deliver topical agents to the wound. Those topical agents may include honey, silver, other antimicrobials, or any agent that speeds wound healing.
Hydrogel dressings have a large fluid content, which adds water to the wound bed. Designed for dry or necrotic wounds, these dressings should not be used in highly exudative wounds.
Hydrocolloid dressings are occlusive dressings that are nearly impenetrable to bacteria. They can donate fluid to the wound and are useful in dry wounds. The dressing permits autolytic debridement by keeping the wound moist. Hydrocolloid dressings should be used with caution in veterinary patients. Due to differences in skin physiology, these dressings do not adhere well to the skin of most veterinary patients.
Hydrofoam dressings may be composed of polyurethane or silicone. Many of the newer dressings also incorporate nanocrystalline silver. Because of the nature of the foam, these dressings can absorb significant exudate. In addition, they can add some protection to the wound. A compressive bandage around the dressing may compromise some of the beneficial effects of a foam dressing.
Alginate dressings usually contain calcium and may also be combined with silver or honey. Indicated for exudative wounds, these dressings absorb wound exudate to form a gel on the wound surface. Alginates also have some hemostatic benefits and cause minimal pain on removal. They are contraindicated in dry wounds.
Microcurrent wound dressings (MCDs) are those that supply a low-level microcurrent to the wound to aid with healing. The original dressings were bulky items requiring a power source. Newer technology has allowed development of small wireless MCDs using a dot matrix design of alternating metals in the dressing. The low-level electrical current is created by the contact of the MCD with moisture from the wound exudate. The MCD affects wound healing through multiple mechanisms. In the inflammatory phase, MCDs may reduce the duration of inflammation in addition to having antibacterial effects. In the proliferative phase, MCDs appear to enhance angiogenesis, attract fibroblasts, and speed re-epithelialization.
Antimicrobial dressings are available in multiple forms and usually contain either metallic nanoparticles, honey, or polyhexamethylene biguanide. These dressings are indicated if bacterial contamination is suspected of slowing wound healing. They should be used for as long as two weeks and then reassessed. If there is no improvement, the choice of dressing should be reassessed.