Wound healing is an uncomplicated process in animals for the most part, but challenges do arise. Fortunately, veterinary medicine has seen significant advances in wound management.
“We have made great strides in our understanding of wound healing and the subcellular interactions that occur among growth factors, cytokines and other cells to create the extracellular matrix needed for wound healing,” says Bryden J. Stanley, MVetSc, MACVSc, Dipl. ACVS. “This understanding allows us to optimize the wound-healing environment.”
Most of the wounds that veterinarians treat are acute because of trauma, such as those suffered in a car crash or in a fight with another animal. Acute wounds include lacerations, punctures and degloving, or shear, injuries, according to Dr. Stanley, an assistant professor in the department of small animal clinical sciences at Michigan State University’s College of Veterinary Medicine.
Nicole Heinrich, DVM, whose practice is limited to dermatology, sees her share of chronic wounds in patients treated at McKeever Dermatology Clinic in Eden Prairie, Minn. With animals, “chronic” describes wounds that heal slowly because of an underlying condition.
After VAC therapy, Blueberry’s wound was sutured on day 4. Therapy was continued for one more day to avoid complications and the patient was sent home the following day.
“Dogs and cats can have underlying diseases like allergies or autoimmune diseases that can lead to secondary skin infections,” Dr. Heinrich says. “Because the skin is compromised by the underlying disease, these lesions can take a long time to heal, sometimes months.”
Wound healing involves three stages. First, the body lays down a clot, which acts as scaffolding on which the new tissue can build. The second phase is repair and proliferation, during which the wound contracts and granulation tissue forms. During the third stage, the granulation tissue is remodeled, and a scar forms.
“Problems can occur in any one of the three phases and delay wound healing,” Heinrich says. “For instance, a bacterial infection can develop, or the dog can sit and lick the wound.”
No matter the type of wound or its location, the basic tenets of healing are to provide healthy tissue linked to a good blood supply. To create this environment, veterinarians may have to:
l Stabilize the patient.
l Debride the wound to remove necrotic and devitalized tissue.
l Lavage the wound to remove debris.
“We need to do a good job with our debridement and lavage of the wound to get the area back to a healthy state. That is a key component,” says Bonnie Campbell, DVM, Ph.D., Dipl. ACVS, a clinical associate professor of small animal soft tissue surgery at Washington State University’s College of Veterinary Medicine.
Moist Environment Is Best
An old wives’ tale states that wounds should be exposed to air and form a scab, but studies have shown that this grandmotherly advice is wrong. Wounds tend to do better in a moist environment so platelets can build the scaffolding and white blood cells, fibroblasts and epithelial cells can migrate through the wound.
“Those cells that are going to build new tissue on the wound function best in a nice, warm environment,” Dr. Campbell says. “When we leave a wound open to the world, it dries out, and it is too cold. The cells cannot do their job appropriately. You don’t want it soaking wet or oozing, but keeping it under a moisture-retentive dressing is usually a good idea.”
No single dressing is appropriate for every wound, the experts say. Before choosing a wound management strategy, do a comprehensive assessment of the animal’s medical history, type of wound, stage and location of the wound, and clinical factors such as the presence or absence of infection.
Then, consider the environment. Is the wound dry and cracking or moist and exudative? A good dressing will absorb fluid without sticking to the wound and causing nonselective debridement that hinders healing. Good choices are foam dressings made from polyurethane and alginates that wick away the exudate but still permit some moisture.
If a wound is dry, a hydrocolloid or hydrogel will create a moister environment. Hydrocolloids protect the area and alleviate friction. Hydrogels have insoluble polymers that debride the wound without harming granulation tissue and encourage cell migration. They are soothing and help ease pain.
The dressing choice may change as the wound heals. For instance, an oozing, infected wound with a lot of exudate may require a foam dressing. As the wound starts to heal and the infection decreases, a hydrogel may be used.
“There are many choices out there for veterinary medicine, so choosing a dressing is no longer a one-size-fits-all situation for animals,” Campbell notes.
Wound management is more than just applying a dressing. Several products help the wounds heal more quickly.
Medical-grade honey has been used as a wound salve for centuries, and ancient Egyptian writings document its healing qualities. Because honey is bacteria static and bactericidal, its use came back into vogue because of antimicrobial resistance.
Stanley has done studies using Manuka Medical Wound Care, manufactured by Links Medical Products Inc. of Irvine, Calif. Australian bees that feed on the menuca tree produce the medical-grade honey, which has more factors that increase its antimicrobial properties and is effective against Staphylococcus bacteria.
“We have used it in a number of cases on both acute and chronic wounds,” Stanley says. “I have used it on goats, cats, dogs, horses and birds. It seems to have a remarkable effect on birds.”
RediHeal Wound Care, produced by Avalon Medical of Stillwater, Minn., is a soft, borate-based bioactive glass dressing, says Heinrich, of McKeever Dermatology Clinic. The material looks likes cotton candy, fills in the wound and supplies the structure for new cells to build on. RediHeal does not need to be removed because it is absorbed into the wound.
“I’ve used it on two dogs and two cats that had chronic disease and were on immunosuppressive medications,” Heinrich says. “The RediHeal reduced bacterial numbers in the skin lesions. It is not an antibiotic, but it creates an environment that is hostile to bacteria.The wound heals more quickly because there is no secondary infection.”
Vacuum-assisted closure (VAC) uses negative pressure and GranuFoam dressing to draw the edges of a wound together, remove infectious materials and promote granulation tissue. KCI Animal Health of San Antonio offers the technology.
“I have used VAC on many different types of wounds, such as large body wounds in a dog that was hit by a car,” Washington State’s Campbell says. “There was gravel and dirt in the wound, and a lot of unhealthy tissue. I did surgical debridement first and then applied VAC. VAC keeps moisture in the wound, lets those white blood cells grow and stimulates the granulation tissue. It doesn’t have to be changed every day, and animals tolerate it well.
“VAC therapy draws fluid through the wound and removes excessive exudates, but still [promotes] a moist environment,” she continues. “The wound heals faster as a result.”
Animals receiving veterinary care are likely to recover from a wound given the number of treatment options, the three experts said.
“A common reason for a wound not healing well in cats and dogs is that it has not been managed appropriately,” Stanley says. “Veterinarians should understand how normal wound healing progresses so they can recognize when they have a wound that is not healing well.”