CHAPTER 156 Wound Care and Management
Wounds of the head, body, and limbs are among the most common equine ailments treated by veterinarians. New graduates are introduced to basic wound management techniques early in their professional careers. There is no single “right” way to treat any given wound; however, several basic wound management principles may be applied to a variety of wounds and will lead to a successful outcome in most cases. These principles are based on common sense and should be used in conjunction with a thorough physical examination, a thoughtful plan, and meticulous aftercare to achieve optimal results. Attention to detail and frequent reassessment of wounds are critical to a successful outcome.
Many excellent resources are available for in-depth reading on wound management and repair. These have been included in the Suggested Reading, and the reader is encouraged to investigate these materials further. The following information is designed for a general update and quick reference.
Wound healing is a complex series of molecular and cellular events and continues to be the source of endless research projects. Interactions occur between a variety of cell types; the bioactive proteins, such as cytokines and growth factors, that they produce; and the extracellular matrix in which these interactions occur. Historically, wound healing is described to occur in three temporally related, overlapping phases: acute inflammatory phase, proliferative repair phase, and remodeling phase. A functional understanding of these phases and how they affect the healing process in various wound types is critical to the ability to formulate an appropriate treatment plan that will ensure the best possible outcome. As a more complete understanding of the molecular and biochemical events that are activated during the repair process is elucidated through ongoing research, new therapies will continue to be developed and become available to veterinarians. The reader is encouraged to check the current literature for new developments that can be applied to the treatment of wounds in horses.
A methodical, organized approach to wound management is vital to a successful outcome. The first step in this process is compilation of a complete history detailing the duration of the wound, cause of the wound, previous treatments applied, degree of lameness, and tetanus toxoid status. This information will enable the practitioner to develop an initial plan, gather appropriate supplies and assistance, and advise the owner as to general prognosis associated with the injury. On arrival at the farm or stable, assessment of the general working environment, the horse’s physical and mental condition, and the general nature of the wound are important. The initial few minutes following arrival are critical to the development of a general plan of action. Immediate intervention may be necessary to control hemorrhage, stabilize a fractured limb, or quiet a frantic horse.
The examination should take place in a clean controlled environment that will allow a thorough assessment, which may require transport to another location. An initial decision should be made whether the wound can be managed with the horse standing or whether general anesthesia will be required. If general anesthesia is likely, immediate care should be provided in the field, and more intensive care and assessment may be provided at the referral center. If the horse is to be referred to another veterinarian, consultation with the referral center is recommended regarding administration of medications and initial treatment in the field. The horse should be adequately restrained to ensure a safe, thorough examination. Use of sedation may be necessary; however, the systemic status of the patient must be considered in cases of severe blood loss or shock. Regional or local analgesia are excellent alternatives to general anesthesia for wounds in the distal portion of the limb. A thorough visual inspection of the wound can provide valuable information about the potential for involvement of nearby associated vital structures and additional considerations that might be required for initial care (Figure 156-1). The specifics of the plan will begin to take shape as progress is made through the process of cleaning, lavaging, and exploring the wound.
Figure 156-1 Severe, contaminated degloving wound over the dorsal aspect of the metatarsus with exposed bone and distal skin flap. Wounds such as this require thorough examination to rule out involvement of the distal tarsal joints, fetlock joint, and digital tendon sheath. The ventral flap should not be sharply transected, but should be retained to aid in wound coverage as contraction occurs. The exposed bone is at risk for sequestrum formation. Debridement may require several days of sequential bandage changes. See Color Plate 17, following p. 704.
Every effort should be made to organize supplies and have them readily available as the examination progresses. An assistant capable of retrieving additional supplies and lending a trained set of hands can be invaluable. The use of examination gloves or sterile surgical gloves is recommended to avoid the potential introduction of iatrogenic infection such as methicillin-resistant Staphylococcus aureus from the veterinarian to the horse. The area surrounding the wound should be prepared first. The wound should be protected from further contamination during the course of these initial preparations. This may be accomplished by filling the wound with sterile water-soluble lubricant, holding a saline-soaked sterile gauze sponge over the wound, or packing the wound with saline-soaked sterile gauze.
Excessive hair should be clipped to allow unobstructed evaluation of the wound, inspection for additional lacerations and puncture wounds, and removal of surrounding dirt and debris. It can be helpful to wet the hair before clipping to allow the hairs to clump together rather than becoming airborne and adhering to the wound. Generally the hair can be removed with a “scooping” motion away from the wound at the end of the clipper pass so that the hair is removed from the immediate wound location. In general, use of a no. 40 clipper blade is adequate; however, gentle application of a safety razor may be helpful in removing tufts of hair from the wound margins. Following hair removal, the surrounding skin is cleaned to remove gross contamination using a gentle soap, such as baby shampoo, that rinses off easily. Care should be taken to protect any open wounds from contact with the soap, as detergent is toxic to fibroblasts. This initial rough scrub should be followed by application of a disinfectant such as povidone-iodine or chlorhexidine scrub. The same principle holds true with respect to detergent in the wound. These preparations may come within a centimeter of the wound margins if one is careful. The initial detergent preparations may be removed with water, saline solution, or isopropyl alcohol. Do not allow alcohol to come in contact with the wound.
WOUND PREPARATION AND EVALUATION
Once the surrounding area is clean, the focus is switched to the wound itself. It is important that any preparations used within the wound itself should be carefully selected so as to avoid substances that are toxic to fibroblasts, epithelial cells, and any other cells present in the wound, as the cellular contribution to wound healing is critical. Preparations that should not be used because of their cytotoxic effects and damage to microvasculature include hydrogen peroxide, povidone-iodine in concentrations greater than 0.1% to 0.2% (10 to 20 mL/1000 mL), and chlorhexidine diacetate in concentrations greater than 0.05% (1:40 dilution; 25 mL/1000 mL). Inactivation of povidone-iodine products by organic debris should be considered in the selection of antiseptics; however, initial gross removal of debris followed by use of a povidone-iodine product is a suitable choice. Thorough wound lavage takes a significant amount of time, and patience should prevail at this stage. Wound exploration, especially of deeper structures, should be reserved for when the wound has thoroughly been lavaged to prevent iatrogenic introduction of bacteria and debris into deeper structures.