Initial Wound Management in Small Animals

Wound lavage serves two purposes. Irrigation of the wound washes away both visible and microscopic debris. This reduces the bacterial load in the tissue, which helps decrease wound complications. The lavage also allows better examination of underlying tissues. Assuming the solution is nontoxic, the most important factor in wound lavage is use of large volumes to facilitate removal of debris. Wound lavage is most effective when delivered under appropriate pressure. A recommended lavage system delivers moderate pressure with a 35-mL syringe and a 19-gauge needle to generate 8 lb/sq in. of pressure. Excessive pressure causes a detrimental side effect by driving debris deeper into the healthy tissue. The use of antibiotics in the lavage fluid is controversial.

The ideal lavage fluid should be antiseptic and nontoxic to the healing tissues. Although isotonic saline is not antiseptic, it is the least toxic to healing tissue. Surgical scrub agents should not be used because the detergent components are damaging to tissue. Dilute antiseptics can be used safely. Chlorhexidine diacetate 0.05% has sustained residual activity against a broad spectrum of bacteria while causing minimal tissue inflammation. However, gram-negative bacteria may become resistant to chlorhexidine. Stronger solutions of chlorhexidine are toxic to healing tissue. Povidone-iodine is an effective antiseptic, but it has minimal residual activity and may be inactivated by purulent debris. Although an effective antiseptic Antiseptics and Disinfectants , hydrogen peroxide is toxic to healthy tissue and should not be used for lavage of wounds.

After wound preparation and hair removal, debridement can be performed. Debridement may involve removal of large segments of tissue (nonselective) or may be performed in a more selective manner, enabling preservation of specific tissues. Skin and local tissue viability should be assessed before any attempted debridement. Skin that is blue-black, leathery, thin, or white is usually not viable. This necrotic tissue should be sharply excised. The debridement may be done in layers or as one complete section of tissue (en bloc resection). Tissues that have questionable viability or are associated with essential structures such as neurovascular bundles should be treated conservatively. Staged debridement is indicated in some situations. In addition to sharp dissection, debridement may be performed mechanically, enzymatically, or biologically (maggot therapy).

After initial inspection, lavage, and debridement, a decision must be made whether to close the wound or to manage it as an open wound. Considerations include the availability of skin for closure, wound location, and the level of contamination or infection. If the wound is left open, it should be managed for optimal healing.

Although primary closure is the simplest method of wound management, it should be used only in appropriate situations to avoid wound complications. Wounds may be closed with suture, staples, or cyanoacrylate. Clean wounds that are properly debrided usually heal without complication. With a primary closure, the layers should be individually closed to minimize “dead space” that might contribute to seroma formation. The types of suture and suture patterns used depend on surgeon preference, the size of the wound, the location of the wound, and the size of the animal.

Primary closure may not be appropriate for a grossly contaminated or infected wound. Therefore, if closure is a goal, it may be delayed until the contamination or infection is controlled. The wound can be managed short-term as an open wound until it appears healthy. At that time, the wound can be safely closed with minimal risk of complications. The time between initial debridement and final closure varies according to the degree of contamination or infection. Minimally contaminated wounds may be closed after 24–72 hours. Longer periods may be required for heavily infected wounds.

Wounds closed >5 days after the initial wounding are considered to be secondary closure. This implies that granulation tissue has begun to form in the wound before closure.

When a wound cannot or should not be closed, open wound management (ie, second-intention healing) may be appropriate. Such wounds include those in which there has been a loss of skin that makes closure impossible or those that are too grossly infected to close. Longitudinal degloving injuries of the extremities are especially amenable to open wound management. Open wound management enables progressive debridement procedures and does not require specialized equipment (such as may be needed with skin grafting). However, it increases cost, prolongs time for healing, and may create complications from wound contracture.

Open wound management is based on repeated bandaging and debridement as needed until the wound heals. Traditional therapy calls for wet-to-dry dressings initially. The initial wide meshed gauze dressings help with mechanical debridement at every bandage change. Until a granulation bed forms, the bandage should be changed at least once daily. In the early stages of healing, the bandage may need to be changed as often as twice daily. After granulation tissue develops, the bandage should be changed to a dry, nonstick dressing so the granulation bed is not disrupted. Both the granulation bed and the early epithelium are easily damaged, and disruption of the granulation bed delays wound healing.

With the concept of moist wound healing, bandaging is combined with autolytic debridement to promote wound healing. The use of moist wound dressings keeps white cells healthier, allowing them to aid in the debridement process. A variety of dressings are available. With these newer dressing options, some consider traditional wet-to-dry dressings to be outdated.

A decision to use open wound management or delayed wound closure is based on several factors. These may include patient morbidity, cost, wound location, and the technical expertise required for closure. In certain patients, surgery may not be an option given their health status. For those patients, open wound management is a better choice. Although the initial cost of surgery is higher than bandage changes, the overall cost may be less expensive depending on the nature and length of wound care required without surgical intervention. Wound location also has a significant impact on the decision to surgically intervene. As the open wound heals, contracture of the wound begins to occur. Contracture of a wound on the lateral thorax may not result in any long-term complications. However, a wound spanning or adjacent to a joint may result in loss of longterm joint function or range of motion due to scarring.

To avoid this loss of function, the wound should be surgically closed. An important component of decision making in these cases relates to the clinician's abilities. If the techniques required for closure exceed the clinician's expertise, referral to another location for closure may be advisable to avoid unnecessary complications. Finally, the owner may have a specific request regarding cosmetics. Closure with open wound management will result in a hairless scar. For various reasons, this may not be acceptable. In those cases, surgical intervention is required.