While waiting for the veterinarian to arrive, gently cleanse the wound to minimize contamination and potentially reduce the risk of complications.
Photo: Anne M. Eberhardt/The Horse
Wound care is one of those many horse issues where there are as many opinions as there are horse owners. There are hundreds of agents (both commercial and homemade) available to paint, spray, smear, gob on, and cover wounds. You can use yellow ones, black ones, red ones, purple ones, and some people have tried very strange ones (used motor oil, for example). On wound care I am a minimalist; many available wound concoctions have actually been shown to delay wound healing or damage the tissue.
I often answer the question, "Is this OK to put such and such on a wound?" with "Would you put it on an open cut on your own arm?" The answer usually is a resounding "No!" Then why would you put it on your horse? More on these later.
Most wounds involve some degree of blood loss (a fact that can be extremely alarming to some people). Because of that, I think it would be useful to review some facts about blood and the horse.
Pop quiz: How much blood does a horse have? It varies some from breed to breed, but an average value is 80 mL (cc) per kilogram of body weight. So, the average 1,200-pound horse (545.5 kilograms) has about 43.6 liters or 11.4 gallons of blood.
So, if the average horse has about 11.4 gallons of blood, how much can be lost before the danger of shock becomes significant? The general rule of thumb is that an animal will start to show signs of blood loss shock when 10% of its blood volume has been lost. Based on the averages, the adult 1,200-pound horse can lose up to 1.4 gallons of blood before serious concern. Most bleeding from wounds appears to be a much larger volume of blood than it actually is, but any time there is hemorrhage, there should be an attempt to control it.
The first rule of minimizing blood loss is pressure. Your first aid kit should contain leg wraps, padding and gauze sponges, and elastic bandage material. If the wrap is too thick, it might not be able to apply an adequate amount of pressure to effectively control bleeding. The bandage should be applied tightly and smoothly, so that it applies significant pressure directly over the wound (if possible)—more on alternatives later.
Signs of blood loss shock include weakness, sweating all over, colic, progressively elevated heart rate, and pale/white mucous membranes (inside lips and gums).
How Wounds Heal
The healing of wounds has been very heavily studied and is broken down into a number of distinct stages. The stages are not absolute—the processes blend together and are subject to many environmental factors that can interfere with the normal wound healing process (infection being the number one inhibitor of wound healing).
The first healing stage is called the immediate stage and spans time zero to one hour. In this stage four things happen:
- The skin retracts and the wound enlarges (this is obviously affected by the location and how much "extra" skin there is).
- The blood vessels in the area contract and slow blood loss from the wound (success depends greatly on the size of the lacerated blood vessels). Vessel constriction is short-lived and is followed by a dilation of blood vessels and an influx of chemicals that attempt to clot the bleeding vessels.
- After about 30 minutes there is an influx of white blood cells and blood clotting cells move into the area. Some of the white blood cells actually contribute to the inflammation that is starting to occur.
- In about 45-60 minutes a clot forms, followed by a scab that then starts to shrink.
Following the "immediate stage" is the so-called "early stage" (1-24 hours). During that time inflammation and debridement of the wound occurs. White blood cells are responsible for the inflammation and for killing any bacterial contaminants to the wound (if they are not overpowering). After the inflammation and killing phase, another type of cell comes in and acts as the "clean-up" crew, digesting debris in the wound bed. Later, there is an influx of cells that will start the repair phase and generation of new tissue. Finally, epithelial (skin surface) cells begin to migrate into the injured area from the normal edges of the wound.
The "intermediate" phase occurs over the next seven days. During that time blood vessels grow into the wound bed, bringing in new healing factors and helping remove damaged tissue. Next is the influx and development of granulation tissue, which is comprised of a variety of cells that can become more substantial tissue, including muscle tissue. But remember that many wounds do not heal with the original tissue—much of the replacement tissue can be a fibrous scar tissue that does not carry quite the same function as the original tissue that was injured.
Near the end of this period, the wound contracts. This is when the skin edges are pulled together, and the wound bed shrinks.
The final steps of wound repair occur in the "late stage" after seven days. At this time, if the damaged tissue has any regenerative capabilities, it is starting to mature. If the damaged tissue does not have much regenerative capability, scar tissue is maturing and doing its final remodeling.
There are many factors that affect the healing stages of a wound—infection, location, type of tissue, how much tissue is missing, and type of damage (was it a clean, surgical-type cut or a rough, jagged one?). Remember, the sooner a severe wound is noticed and receives veterinary attention, the better the prognosis.
Fresh, profusely bleeding limb wounds will need to have a pressure bandage applied immediately. Try to stay calm—a relatively small, non-life-threatening quantity of blood can look like a much greater quantity (remember that a horse has to lose upwards of 1.4 gallons of blood before there is a severe problem). A pressure bandage compresses the hemorrhaging blood vessels and helps promote blood clotting. If a large artery is severed, it can be hard to apply enough pressure, especially if the laceration is someplace other than the lower limb, but an attempt should be made.
The immediate bandage should not be too thick, as this will limit its ability to apply enough pressure for bleeding control. Generally, three sheets of sheet cotton, a shipping bandage quilt, a large bath towel appropriately folded, or several layers of roll cotton is sufficient and can be applied with several rolls of elastic bandage material. The elastic bandage material should be applied in a smooth, even, and firm manner—there must be adequate pressure if it is to be effective in controlling hemorrhage. This sort of bandage might be too tight for long periods of time, but can effectively control bleeding. Leave the bandage in place for 20-30 minutes, then replace it with new material applied snugly. If the bleeding has subsided, apply a clean and more normally applied support bandage.
If the laceration involves the flexor tendons or suspensory ligament, it's important to provide support and immobilization. A Robert Jones bandage (a layered and padded bandage to limit limb mobility) and splinting should be applied for transportation or while waiting for veterinary evaluation. This support and immobilization might help prevent further damage to the injured area. The horse should be moved as little as possible until he has been evaluated and treated.
If the wound is older, bleeding might have subsided or slowed, but there could be contamination with dirt, debris, and bacteria. In wound repair, there is a "golden period," thought to be the first six hours after initial injury. If the wound is appropriately cleansed and treated during that time, chances of complication from infection and subsequent repair breakdown are reduced. Therefore, it is important to have wounds evaluated and treated as soon as possible.
In the interim, cleanse the wound with warm water and a mild soap or dilute chlorhexidine solution to minimize contamination and potentially reduce the risk of complications. Applying a sterile dressing and support bandage can help a lot, especially if the veterinarian can't come right away. If the wound is very old (with dried-out skin edges, obvious infection, or pus), swollen, and inflamed, hose it with water to reduce inflammation and clean it until a veterinarian can properly debride the wound.
As stated before, there are many concoctions—commercial and homemade—to put on wounds. However, many commercial creams, ointments, and sprays have been shown to inhibit the normal healing response. My preference, unless there is a strong indication to do otherwise (talk to your veterinarian), is to keep the wound as clean and dry as possible and leave most of the wound preparations in the bottle.
One substance horse owners often use, but should leave in the bottle, is hydrogen peroxide. The commercially available 3% hydrogen peroxide solution is a relatively poor anti-microbial agent and can cause tissue damage while producing gas within the wound and under the skin. Ask your veterinarian for suggestions of topical products that can be used safely to heal wounds.
One of the best ways to deal with proud flesh is to do all you can to prevent its development through immediate treatment. Keep the wound as clean and dry as possible, and use a firm support bandage to reduce the chance of proud flesh development. Wounds on the lower limbs are primary sites for proud flesh. Proud flesh (exuberant granulation tissue) is the healing process gone crazy, with over-production of granular healing tissue. This overwhelms the wound bed and doesn't allow the skin edges to meet up and heal properly. The major treatment for proud flesh is surgical removal and treatment so the skin edges can grow together.
There are many chemical agents designed to destroy granulation tissue, which can be used alone in mild cases or with surgical debridement. The removal of proud flesh can be a time-consuming, frustrating procedure, and should always be done under veterinary supervision.
Granulation tissue contains many blood vessels, and in severe cases, there can be substantial blood loss during treatment. In addition, in severe cases of proud flesh (or very large wounds in general), skin grafting might be necessary for adequate healing.
In addition, during summer a wound with excessive granulation tissue can become infected with fly larvae, which then cause "summer sores" (which can mimic a good case of proud flesh). These cases require special treatment as well—another reason for veterinary consultation. Again, the best way to deal with proud flesh is to prevent it by detecting and appropriately treating wounds early.
On a final note, one of the most important aspects of wound management is tetanus protection (if a booster is needed) before and after an injury. Remember that even a surgical incision can cause tetanus. Vaccination records for all your horses should be easily accessible so that you can check quickly to see if a booster is necessary. Very few horses die from wounds, but horses do die from tetanus--and tetanus is completely preventable. Don't guess—know your horse's vaccination status.
About the Author
Michael A. Ball, DVM, completed an internship in medicine and surgery and an internship in anesthesia at the University of Georgia in 1994, a residency in internal medicine, and graduate work in pharmacology at Cornell University in 1997, and was on staff at Cornell before starting Early Winter Equine Medicine & Surgery located in Ithaca, N.Y. He is also an FEI veterinarian and works internationally with the United States Equestrian Team.
Ball authored Understanding The Equine Eye, Understanding Basic Horse Care, and Understanding Equine First Aid, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.
POLL: Colic Surgery