Wound healing techniques: what vet techs need to know
ORLANDO, FL – There are many products on the market to facilitate wound healing ‘supported’ by anecdotal case reports and practitioner testimonials. However, there is no perfect liquid, gel, spray, foam, or contact layer on the market, said Steve J. Mehler, DVM, DACVS, presenting at the North American Veterinary Conference. Each has their own benefit in wound healing but they all have wound suppressing properties as well. Dr. Mehler said that knowing the positives and negatives of the commonly used wound products and the ideal time to use them in wound healing is important when trying to maximize a positive outcome.
Open or closed wounds
A normal skin wound heals within two to four weeks. Healing can be delayed by local or systemic factors; local factors that we can control include surgical technique and experience, blood supply, tension, presence of infected or devitalized tissue, mechanical stress, shape of the wound, iatrogenic foreign material (suture material, implants), and foreign bodies. Systemic factors include comorbidities, hypoproteinemia, hypovolemia, edema, malnutrition, age, immunodeficiency, and drugs.
A wound that is not clipped, cleaned, and debrided appropriately will not heal and the systemic signs associated with the wound will not subside. If there is any doubt whether a wound is contaminated or contains devitalized tissue, open wound management is indicated prior to closure. It allows for continued wound drainage, regular wound inspection, lavage, and debridement.
Wound healing phases
- Inflammatory phase, with the initial clot formation and migration of neutrophils
- Proliferative phase, during which fibroblasts and endothelial cells migrate into the wound
- Maturation and remodelling
Topical agents for wounds should fulfill certain basic criteria
- Sterile and non-toxic
- Non-irritant (painless and hypoallergenic)
- Simple application
- Maintain a moist wound environment
- Cost effective
- Promote wound healing
The practices of saline irrigation of the wound and further debridement with saline- soaked, wet-to-dry dressings are very common today in veterinary medicine. It is widely accepted that following appropriate wound care, the ongoing debriding effects of wet-to-dry dressings can convert a contaminated wound to one with a “clean-contaminated” status in several days.
What do vets and techs want in a wound care product?
- Application and removal should be painless
- The product should be relatively simple to apply and change
- A product that safely and conveniently can be changed every 3 days
- Minimal adverse effects or complications associated with use of the product
- Reasonably priced
- Controlled, clinical and experimental studies that validate the product
- A highly effective and efficient product
The timing of wound closure
There are four types of closure options: primary closure, delayed primary closure, secondary closure, and second intention healing. Dr. Mehler said that a general rule of thumb is that clean and fresh wounds with minimal local crushing injury may be closed primarily – before granulation tissue forms, usually after about three to five days. Delayed primary closure is performed in clean-contaminated wounds (penetrating wounds and some bite wounds), with questionable tissue viability. Open wound treatment and wound lavage for three to five days is commonly necessary. In contrast, contaminated wounds are usually closed after the appearance of granulation tissue. Initial debridement and open wound treatment are necessary, allowing the elimination of contaminated and devitalized tissue. Secondary closure can be performed at five to seven days. With large skin defects, severe contamination, the appearance of necrotic tissue, or if there are financial constraints, a wound may heal by second intention, but the cosmetic and functional result with this type of wound closure may be inferior.
Traditional and modern wound management
Traditional early open wound treatment is performed using adhesive bandages in the form of wet-to-dry or dry-to-dry contact layers. These bandages are used for continued debridement and are discontinued once granulation tissue has formed. Once a granulation bed has formed, the wound may be closed or a nonadhesive contact layer is used. Examples of nonadhesive contact layers include:
- Foams (Hydrasorb)
- Alginates (Algisite)
- Hydrogels (Curafil)
- Perforated film dressings (Opsite)
- Petroleum impregnated dressings (Adaptic)
- Synthetic micropores (Telfa)
Each of these products has an ideal wound type or wound phase when they should be used. With any of the above-mentioned products an intermediate layer, like cast padding and an outer layer to protect the bandage, are necessary to complete the bandage. Dr. Mehler stressed not to use plastic bags, plastic wraps, or diapers around the wounds, as the wound and bandage need to breath.
Antibiotics
The use of local, topical, or systemic antibiotics in wound management is, at best, controversial. If used, the decision of which antibiotic is based on tissue culture and sensitivity results. To prevent nosocomial or highly resistant infections and prolonged suffering of the patient, radical debridement and lavage is preferred over the inappropriate and indiscriminate use of antibiotics. As soon as healthy granulation tissue appears in the wound, the risk of local infection decreases significantly.
Silver
Topical silver has been used for many years, especially for the treatment of burns. Silver has a wide antimicrobial activity, lacks toxicity, and enhances epithelialization of wounds. Despite its common use by veterinary wound care practitioners, no large, controlled studies are found in the veterinary literature.
Tripeptide copper complex (TCC)
The wound healing enhancing effects of this molecular complex (originally isolated from human plasma) has been well established, including increased neovascularization, epithelialization, collagen deposition, and wound contraction.
Hyaluronic acid
In animals, hyaluronic acid (HA) is synthesized and extruded from the cell membrane of fibroblasts. Gels, membranes, powders, lightly woven meshes, and sheets of solid material can be made with HA. Several case examples have been presented by a veterinary company that sells such a product but a randomized, controlled, experimental study has demonstrated conflicting results.
Honey
Honey has been used to treat wounds for over 4000 years, and has been shown to have antibacterial properties additional to its hyperosmolar properties. Unpasteurized honey has also been shown to accelerate wound healing in mice. It appears that Manuka honey has the best antibacterial effect and provides superior tensile strength for healing burn wounds in rats. There are no controlled clinical studies in veterinary medicine.
Negative pressure wound therapy (NPWT)
Vacuum assisted closure has been shown to be effective in the treatment of traumatic and chronic wounds. The therapy decreases interstitial edema, increases perfusion to the wound and periwound, and the mechanical strain on the fibroblasts appears to increase proliferation and collagen synthesis. Its use in veterinary medicine is extremely promising, with one of the advantages being prolonged time between dressing changes (up to 72 hours). Last month a revolutionary NWPT device was developed and released for the veterinary market. The Infiniti Curato™ is a disposable device that is programmed for 30 days of use and can be used on multiple patients. It is the only device in the veterinary market that enables the veterinarian to infuse the wound with any topical solution or medication during vacuum assisted therapy, has a novel self-sealing adhesive barrier, and has the strongest adhesive disc available to prevent premature removal of the disc by the patient.
Dr. Mehler concluded by saying that many other wound healing products on the market exist that need to be tested in randomized, controlled studies. For example, pulsed electromagnetic fields, low intensity laser, topical hyperbaric oxygen therapy, sugar, maltodextrin, acemannan and aloe vera are just a few that may have the potential to transform wound healing in veterinary medicine. CVT
