Wound Bandages and Dressings for Small Animals

The goals of bandaging include the following:

• limiting hemorrhage

• immobilizing the area

• preventing further trauma or contamination of the wound

• preventing wound desiccation

• absorbing exudate

• controlling infection

• aiding in mechanical debridement of the wound

When bandages are constructed, 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 (also called the contact layer) directly contacts the wound to allow tissue fluid to pass through to the secondary layer and may be an adherent or nonadherent dressing.

Nonadherent dressings contact the wound without sticking and may be semiocclusive (allowing air to penetrate and exudate to escape from the wound surface) or occlusive (impermeable to air and fluid). A nonadherent dressing is usually a fine mesh or foam nonstick material embedded with paraffin or a petrolatum-based ointment or coated with a thin polymer to prevent sticking to the wound. 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 this type of bandage is nonselective, healthy tissue may also be damaged.

Adherent bandages are classified based on the composition of the primary layer:

• Dry adherent bandages (also called dry-to-dry bandages) consist of dry, absorbent, wide-mesh gauze applied to the wound and removed after the primary layer has absorbed fluid and debris and then dried. The bandages are painful to remove but enable appreciable tissue debridement.

• Wet adherent bandages (also called wet-to-dry bandages) are made with sterile, wide-mesh gauze moistened with saline (0.9% NaCl) solution, placed directly on the wound and removed after the primary layer has dried (pulling debris and exudate away from the wound by wick action). They are also painful to remove but result in less tissue desiccation than dry adherent bandages.

A wet-to-wet bandaging technique is similar to that used for a wet-to-dry bandage, except that the contact layer is not allowed to dry before bandage removal. 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.

Pressure necrosis complication, dog

Image

Courtesy of Dr. Kevin Winkler.

Bandages have a number of potential complications. Bandages that are 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 have the following attributes:

• nontoxic

• protects the wound

• keeps the environment moist

• minimally painful to the patient

• cost-effective

Dressings 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 other 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. These dressings can cause maceration of healthy periwound tissue.

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 can cause maceration of healthy periwound tissue. Because of 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 substantial exudate. In addition, they can add some insulation and 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 and should not be used over exposed bone or tendon.

Microcurrent dressings (MCDs) supply a low-level microcurrent to the wound to aid with healing. The original MCDs 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 decrease 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 up to two weeks and then reassessed. If there is no improvement, the choice of dressing should be reassessed.

• Fossum TW. Small Animal Surgery. 4th ed. Elsevier Mosby; 2013.

• Mann FA, Constantinescu GM, Yoon H. Fundamentals of Small Animal Surgery. Wiley-Blackwell; 2011.

• Tobias KM, Johnson SA. Veterinary Surgery: Small Animal. Elsevier Saunders; 2012.

• Also see pet health content regarding bandages and dressings.