Wound management is commonly performed by nurses/technicians. This lecture will focus on management of open wounds, which are often the most difficult wounds to treat and are those that require the most expertise and time to achieve a good outcome.

Immediately after injury, or when the animal is brought for treatment, wounds should be covered with a clean, dry bandage to prevent further contamination and hemorrhage. Life-threatening injuries should be treated and the animal's condition stabilized before further wound management is undertaken. When appropriate during stabilization, bandages should be removed and the wound assessed and classified as either contaminated or infected and as an abrasion, laceration, avulsion, puncture, crush, or burn wound. The "golden period" is the first 6 to 8 hours between wound contamination at injury and bacterial multiplication to greater than 10⁵ CFU per gram of tissue. A wound is classified as infected rather than contaminated when bacterial numbers exceed 10⁵ CFU per gram of tissue. Infected wounds often are dirty and covered with a thick, viscous exudate.

Fundamentals of wound management:

 Temporarily cover the wound to prevent further trauma and contamination.

 Assess the traumatized animal and stabilize its condition.

 Clip and aseptically prepare the area around the wound.

 Culture the wound.

 Débride dead tissue and remove foreign debris from the wound.

 Lavage the wound thoroughly.

 Provide wound drainage.

 Promote healing by stabilizing and protecting the cleaned wound.

 Perform appropriate wound closure.

Abrasions are superficial and involve destruction of varying depths of skin by friction from blunt trauma or shearing forces. Abrasions are sensitive to pressure or touch and bleed minimally. A laceration is created by tearing, which damages skin and underlying tissue. Lacerations may be superficial or deep and have irregular edges. Avulsion wounds are characterized by tearing of tissues from their attachments and creation of skin flaps. Avulsion injuries on limbs with extensive skin loss are called degloving injuries. A penetrating or puncture wound is created by a missile or sharp object, such as a knife, pellet, or tooth that damages tissue. Wound depth and width vary depending on the velocity and mass of the object creating the wound. The extent of tissue damage is directly proportional to missile velocity. Pieces of hair, skin, and debris can be embedded in wounds. Crush injuries can be a combination of other types of wounds with extensive damage and contusions to skin and deeper tissue. Burns may be partial- or full-thickness skin injuries caused by heat or chemicals.

Wounds less than 6 to 8 hours old with minimal trauma and minimal contamination are treated by lavage, débridement, and primary closure. Generally, the sooner treatment begins, the better the prognosis. Penetrating wounds should not be primarily apposed without surgical exploration. Severely traumatized and contaminated wounds, wounds older than 6 to 8 hours, or infected wounds should be treated as open wounds to allow débridement and reduction of bacterial numbers. Most wounds are surgically apposed after infection has been controlled; however, some wounds heal by contraction and epithelialization (healing by secondary intention).

Often anesthesia is required for initial wound inspection and care. The objective of open wound care is to convert the open, contaminated wound into a surgically clean wound that can be closed. Aseptic technique, gentle tissue handling, and hemostasis are essential. Severely contaminated or infected wounds should be cultured after initial inspection. The area surrounding the wound should be widely clipped and prepped. The wound may be protected from clipped hair and detergents by applying a sterile, water-soluble lubricant (K-Y Jelly) or by placing saline-soaked sponges in the wound and covering with a sterile pad or towel. As an alternative, the wound may be temporarily closed with sutures, towel clamps, staples, or Michel clips. Hair may be clipped from the wound margin with scissors dipped in mineral oil to prevent hair from falling into the wound. Povidone- iodine or chlorhexidine gluconate skin scrubs are used to prepare clipped skin. The detergents in antiseptic scrubs cause irritation, toxicity, and pain in exposed tissue and may potentiate wound infection. Alcohol is very damaging to exposed tissue and should be used only on intact skin.

Initial wound management begins with removal of gross contaminants and copious lavage using a warm, balanced electrolyte solution, sterile saline, or tap water (500 to 1000 ml). Sterile isotonic saline or a balanced electrolyte solution (lactated Ringer's solution) is the preferred lavage solution. Tap water is effective and less detrimental than distilled or sterile water, although it causes some hypotonic tissue damage (cellular and mitochondrial swelling). Wound lavage reduces bacterial numbers mechanically by loosening and flushing away bacteria and associated necrotic debris. Lavage may be facilitated by the use of non-cytotoxic wound cleansers (e.g., Constant Clens, Kendall Co., Mansfield, MA; Allclenz Wound Cleanser, Healthpoint Biotherapeutics). Generally, these cleansers are applied to loosen debris and soften necrotic tissue during bandage changes; they act as a surfactant, disrupting the ionic bonding of particles and organisms to the wound and allowing them to be easily rinsed off with saline or balanced electrolyte solutions. Lavage following application of these cleansers, however, is not necessary. Antibiotics or antiseptics (e.g., chlorhexidine or povidone-iodine) in the lavage solution reduce bacterial numbers; however, these agents may damage tissue. Antiseptics have little effect on bacteria in established infections. Lavaging is preferred to scrubbing the wound with sponges. Sponges inflict tissue damage that impairs the wound's ability to resist infection and allows residual bacteria to elicit an inflammatory response.

Bacteria are effectively removed from the wound surface by high-pressure lavage. Traditionally, a 35- or 60-ml syringe and an 18-gauge needle have been thought to generate approximately 7 to 8 psi of pressure; however, it was recently shown that it generates pressures substantially higher than this (18.4 ± 9.8 psi). The most consistent delivery method to generate 7 to 8 psi is a 1 L bag of fluid within a cuff pressurized to 300 mmHg (Fig. 16–3). Higher pressure (70 psi), generated by pulsatile lavage instruments (i.e., Water Pik [Teledyne], Surgilav, or Pulsavac débridement system), is more effective in reducing bacterial numbers and removing foreign debris and necrotic tissue, but may drive bacteria and debris into loose tissue planes, damage underlying tissue, and reduce resistance to infection. Bulb syringes or fluid bottle with holes made in the cap do not generate enough pressure to remove bacteria and debris adequately.

Débridement

Healing is delayed if necrotic tissue is left in the wound. Devitalized tissue is removed from the wound by débridement. Débridement involves removal of dead or damaged tissue, foreign bodies, and microorganisms that compromise local defense mechanisms and delay healing. The goal of débridement is to obtain fresh clean wound margins and wound bed for primary or delayed closure. Devitalized tissue is removed by surgical excision, autolytic mechanisms, enzymes, wet-dry bandages, or biosurgical methods. The extent of devitalized tissue usually is obvious within 48 hours of injury.

Topical Wound Medications

Topical Antimicrobials and Antibiotics

Antimicrobial agents and antibiotics eliminate or reduce the number of microorganisms in a wound that destroy tissue. Topical rather than systemic antibiotics are preferred for open wounds. Mildly or moderately contaminated wounds do not benefit from combined topical and systemic antibiotic therapy; however, combined therapy is advantageous in heavily contaminated wounds. Antibiotics applied within 1 to 3 hours of contamination often prevent infection. Benefits of topical drugs should outweigh their cytotoxic effects. Antibiotics used effectively as topical ointments or added to lavage solutions are penicillin, ampicillin, carbenicillin, tetracycline, kanamycin, neomycin, bacitracin, polymyxin, and cephalosporins. Once infection is established, topical and systemic antibiotics have no beneficial effect in preventing suppuration of wounds undergoing closure. Wound coagulum prevents topical antibiotics from reaching effective levels in tissues deep in the wound and also prevents systemic antibiotics from reaching superficial bacteria. These wounds must be débrided to allow antimicrobial access to bacteria.

Guide to dressings based on purpose