The many types of dressings available to veterinarians possess different qualities with varying effects and risks. So being familiar with and using them properly throughout a horse’s wound-healing process is paramount, said Dean Hendrickson, DVM, MS, Dipl. ACVS, professor of equine surgery at Colorado State University’s College of Veterinary Medicine & Biological Sciences, in Fort Collins.
“You can’t just grab your favorite dressing and use it throughout the whole healing process; you have to use them specifically based upon what’s going on with the wound,” he said during the 2021 American Association of Equine Practitioners convention, held Dec. 4-8 in Nashville, Tennessee.
“We have to get over the perspective that a wound is a wound is a wound,” he said. “They are not the same; they change; they’re different as they go through the healing process. And our dressing should change with them.”
When first evaluating a wound, veterinarians should determine if they can suture it closed—and, if so, do it. “It’s always better to close a wound than it is to let it heal over time,” he said. Wounds with too much tissue loss for closing are strong candidates for a skin graft later in the healing process. Veterinarians can treat some smaller infected wounds first and suture them later.
A wound can present in any of four major phases, each of which should guide the veterinarian’s choice of dressing, Hendrickson said. If it’s:
- Necrotic and/or weeping large amounts of exudate—a yellow liquid—it needs debridement.
- Dry, it needs moistening.
- Healing with poor-quality granulation tissue, it needs dressings that promote healthy granulation tissue growth and wound contraction.
- In the epithelialization phase—when epithelial cells grow and start to cover the wound surface with new top-skin—it needs dressings that maintain the right temperature and humidity levels to support that growth.
Veterinarians should recognize which phase the wound is in—even different parts of the wound, as healing can occur unevenly—and adjust their wound treatment course, Hendrickson said. That can not only optimize healing but also prevent caretakers from making mistakes that impede the healing process.
“If we’re not paying attention to what the wound is telling us, we’re going to keep using the same dressing, and the wound healing is going to slow down,” he said.
Leaving a wound dry and open to the air, said Hendrickson, can make it more inflamed, painful, and itchy, and it can even cause more scarring. Veterinarians should pack dry wounds with a moisturizing dressing like a hydrogel, which “donates” its water to the wound. As long as the dressing stays moist, caretakers can change it every five days until the wound has reached the next phase of healing or is soft and moistened enough for debridement.
Wounds with necrotic tissue and/or infection need regular debriding, starting first with what Hendrickson calls “sharp debridement”—using a scalpel to cut or scrape off the surface of the wound. This phase calls for a debridement dressing with a gauze wrap, which allows for autolytic debridement. In this process, the moist environment encourages the body’s own enzymes to slough off dead tissue. “Autolytic debridement is incredible,” he said.
A saline dressing can work for this but requires constant saline reapplication to the gauze up to six times a day, he said. Hypertonic saline dressings require less intervention and work well on visibly infected wounds and those with large amounts of exudate. They should be changed every three days and can be covered with plastic wrap or a deconstructed rectal exam glove to hold in the moisture. Veterinarians can also choose an antimicrobial dressing or an evidence-based honey dressing, changed every three days—or every five days in surgical wounds (which are especially vulnerable to environmental infection).
Veterinarians also need to understand when to stop using a debriding dressing. And that depends on the wound—“not on the calendar,” Hendrickson said.
“Once the wound has been effectively debrided, you shouldn’t use debridement dressing anymore, because that’s actually just causing more damage to the wound,” he explained.
Clinicians can encourage healthy granulation tissue development by using a seaweed-based product called calcium alginate integrated into soft fabric pads. The product interacts with the sodium in the wound and elicits a mild inflammatory response that can promote healing.
“One of the biggest challenges with horses is that they don’t provide a very good inflammatory response in the early wound-healing stages,” Hendrickson said.
However, calcium alginate is highly absorptive, capable of holding 20 times its own weight, he added. While that’s helpful for very wet wounds, it can draw too much moisture out of wounds with little exudate. So, calcium alginate dressings often need to be moistened with saline and covered with plastic to maintain good wound hydration. They can be changed every five to seven days but no more frequently than every three days. For reasons yet to be determined, calcium alginate appears to be most effective if left undisturbed for three days at a time, Hendrickson said.
Finally, for wounds at the epithelialization phase, veterinarians can use a semiocclusive foam, he said. The dressing can be changed every five to seven days depending on the type of exudate the wound has produced.
While keeping wounds moist is important for healing, and can double the epithelialization rate, it can also put them at risk of bacterial infections and make them more vulnerable to traumatic impacts. With that in mind, veterinarians should observe wounds closely and intervene with debridement and topical antimicrobials but not antiseptics (which can kill healthy tissue), in the event of infection, Hendrickson said.