Out pets’ skin in composed of layers similar to ours: the epidermis on the outside, the dermis below; the subcutis below that; and fat and muscle below that. Wounds can be sterile, unclean (relatively clean but not sterile), or even heavily contaminated. The body is designed to address all of these situations but sometimes they need our help.
There are four phases of wound healing: Inflammation, debridement, repair, and maturation.
Inflammation (Starts immediately)
This is the first phase of healing and is all about controlling bleeding and activating the immune system. Without too much detail, blood clots are forming and blood vessels are constricting to limit blood loss in the area. This process also calls in “clean up” cells of the immune system to address contaminating bacteria and any dead tissue.
Debridement (Starts in a few hours)
Wound fluid, dead tissue, and immunologic cells form pus, which is designed to flow as a liquid from the wound and carry debris with it. The cells that were called to the wound in the inflammation phase are now actively working on consuming dead tissue and cleansing the area.
Repair (Starts in a couple of days)
Collagen begins to fill in the wound to bind the torn tissues, a process that will take several weeks to complete. New blood vessels begin to grow into the area from the uninjured blood vessels nearby. The wound edge begins to produce granulation tissue, the moist pink tissue that will ultimately fill in the wound. The wound will shrink in a process called wound contraction so that new skin can form and cover it.
Maturation (Starts in 2-3 weeks and can take months or even years)
Once plenty of collagen has been deposited, the final phase of scarring can form. The scar becomes stronger and stronger over time as new blood vessels and nerves grow in and the tissue reorganizes. The final result will never be as strong as un-injured tissue but should ultimately achieve approximately 80% of the original strength.
Primary Intention Healing
When the wound is a surgical incision with sutures in place, there is no wound area for the body to fill with granulation tissue. Instead, the wound margins are already held together and the two margins simply need to bond together. New skin begins to form across the margin within two days. The four stages of healing continue as previously noted but go much faster (10-14 days total) because there is no gap in the tissue to fill in. Healing occurs across the wound margin, not down its length, which means long incisions heal just as fast as short ones.
Secondary Intention
If the wound cannot be closed with sutures (too big, too much tension, too infected, etc.), then second intention healing begins. This is where granulation tissue must form to fill in the gap. Once is filled, contraction soon follows, which means the wound will be getting smaller and smaller. Eventually it can be allowed to simply close on its own or, when it is small enough, the margins can be trimmed and the wound surgically closed by primary intention for a smaller scar and better fur coverage. In the right circumstances, skin grafts can be applied but only if there is a healthy granulation bed.
When a wound is cleansed of debris, scabs, crusts (when a bandage is removed), granulation tissue is evident. Some people, especially those not familiar with wound management, may be alarmed by its appearance. It is red or bright pink, bleeds easily, moist, and is often confused with underlying muscle. It looks like it would be sore but its not. Many people incorrectly feel granulation tissue is not supposed to be there when, in fact, it is a sign of a healthy healing wound. It should be moist so as to allow better blood flow and a proper debridement phase (see part one). It bleeds easily as it is rich in blood vessels and is generally not painful as nerves grow into granulation tissue late in the healing process.
Human intervention, when needed
- Pus pockets must be drained. Eventually, will rupture out on their own (it can be a disaster if they rupture in instead of out), but often they will take a great deal of overlying tissue with them. Sometimes in-dwelling drains must be placed surgically to assist in removing harmful fluids.
- The wound must be kept moist. This can be accomplished with bandages and/or ointments. A moist wound has better blood flow and can heal more effectively.
- Gross contamination should be removed. Dirt, hair, pus and other bacteria-rich substances should be flushed from the wound. Antibiotics may be needed either orally, topically, or both to address the infection.
- Dead tissue should be trimmed. If there is nonviable tissue in the wound, it should be removed so the body will not have to liquefy it. This can be done through surgery, through certain types of bandages or by topical applications depending on the type of wound.
- Wound-enhancing topical products are sometimes employed. Some aid to reduce infection and/or stimulate the formation of granulation tissue. (i.e., honey impregnated dressings)
If your pet’s wound is fresh and your pet will allow it, try to flush out large debris particles with tap water (saline flush as used for eyes is even better). Cover the wound with clean, dry bandage material, if possible. See your veterinarian for professional wound care as bandages can cut off circulation to a limb if applied incorrectly.
Non-healing Wounds
Some wounds may become chronic, either relapsing or never show signs of healing. In this case, consult your veterinarian ASAP. Non-healing wounds may have other underlying disease process involvement (ie, tumour) or may simply be infected or have antibiotic resistant bacteria. This is common in human medicine but is becoming more commonplace amongst veterinary patients. Do not try to do it yourself and end up with an advanced and possibly untreatable problem.
Referenced from https://www.vin.com/
Written by Dr. Alex Hare