Large animal wounds

Wound management

Medications

NSAIDs will slow wound healing but so will swelling. NSAIDs are useful to control the initial inflammation (first 72 hours) but then should be discontinued. Most horses are not painful after the incident. Signs of pain would indicate deeper trauma to bone, tendons or ligaments.

Horse NSAIDs – phenylbutazone, firocoxib, flunixin meglumine

Food animal NSAIDs- flunixin meglumine (approved), meloxicam (off label use)

Systemic antibiotics are generally not indicated unless deeper structures are involved or infection would be life threatening (eg near the chest or abdominal cavity). In these cases, iv antibiotics may be needed.

Regional perfusion of antibiotics can help with deeper wound management in the distal limb. For regional perfusion, a tourniquet is placed on the limb and a dose of antibiotics given iv below the tourniquet, concentrating the drug in the area needed. Antibiotics may also be injected directly into the synovial structures.

 Regional limb perfusion performed on a cria

Once granulation tissue has developed, it will protect the wound from outside contamination. This typically means antibiotic coverage is needed for about 5 days maximum.

Tetanus toxoid

Horses and small ruminants are very sensitive to Clostridium bacteria and to tetanus infection. Any wounded horse, goat, sheep or camelid should be boostered with tetanus toxoid if it has been more than 6 months since the annual vaccine. If a horse has a deep wound and no history of tetanus toxoid, the horse should also be treated with tetanus antitoxin. Tetanus antitoxin does carry the risk of serum sickness (immune response to equine antibodies) and is not given if the horse has been vaccinated previously.

Wounds left to heal by second intention generally do very well, particularly those above the hock or carpus. The wounds should be kept clean and dry, potentially covered by a water based ointment to maintain tissue moisture. Lower limbs may be bandaged until granulation tissue fills the defect. Wounds on the upper limbs or torsos may be difficult to bandage.

Wound debridement

Sharp debridement (using a scalpel to remove damaged or contaminated layers) is less traumatic than rubbing and scraping the wound. Tissues are debrided back to bleeding layers, minimizing debridement to critical structures and over joints.

NOTE: Eyelid wounds should not be debrided; this area has good blood supply but do not tolerate missing skin. Never trim the flap of an eyelid wound; all parts should be reconnected to avoid lid margin scarring and exposure keratitis. If concerned, these cases should be referred. See Eyelid lacerations

Wound closure

After complete evaluation and cleaning, the veterinarian must decide if the wound should be closed primarily, with delayed closure or left to heal by second intention. Many wounds cannot be closed, making the decision easy. If closure is possible, most vets will attempt it. However, it is important to avoid creating an abscess in the area. Ensure the wound can drain ventrally if needed. Often this is most readily done with an incision at the ventral aspect or by leaving the wound partially open. If the incision is made perpendicular to the lines of tension, it will stay open longer. Penrose drains can be used; these should not exit the wound or incision and should be pulled in 2-3 days as they create additional inflammation.

While delayed primary closure can be useful in small animals, in large animals it doesn’t often work as wound retraction occurs, enlarging the wound surface area and making it even harder to close.

Expect dehiscence in areas of high motion or high tension. Warn owners that the wound may fall apart in 2-3 days. Managing the swelling may help. Distal limb casts can support the wound and allow primary closure.

Topical wound agents

If the wound cannot be closed, topical salves may help keep tissues moist and minimize wound healing delays. Water soluble ointments are preferred over oil based ointments. Agents should be safe for new epithelial cells. Avoid toxic compounds. Generally triple antibiotics (neomycin + polymyxin + bacitracin) or silver sulfadiazine are used. Nitrofurazone (yellow goo) and chlorhexidine (blue goo) were used historically but are less commonly used now. Various bacteria can grow in nitrofurazone and it can actually delay wound healing. Chlorhexidine has been shown safe. Efficacy is unknown. Medical grade honey may even improve wound healing and decrease the risk of dehiscence if applied prior to closure.

Drains

Penrose drains can be used to assist drainage of wound fluids. They should not be exited out an incision or healing wound but should exit the most ventral aspect of the pocket. Remember: drains are foreign bodies and will cause additional inflammation. Drains can also wick bacteria into the wound. Generally a drain should be removed in 3-5 days or when the drainage slows. Do not expect drainage to stop with a drain in place. In many cases, extending the incision to the ventral aspect or creating an incision for ventral drainage is more effective.

Restrict motion

Generally limited motion will improve healing. Stall rest without handwalking is recommended at least initially. Bandages and splints may be useful. Horses don’t often like stall rest and extra attention may be needed to improve horse and owner attitudes, including drugs and enrichment activities (for the horse).

Bandaging – lower limb wounds

Generally horse wounds are bandaged initially to prevent further contamination. Bandages do promote granulation tissue formation so are generally only needed in the initial stages of wound healing unless the limb is unstable or bandaging is needed to minimize motion.

Antibiotics and/or antiseptics may be applied to the wound and then the wound covered by a nonstick pad that is held in place with a soft wrap. A support wrap is then placed on the limb. This is often a manufactured bandage or sheet cottons. This layer is held in place with brown gauze or vetwrap. The brown gauze and/or vetwrap is applied snuggly with even tension. Bulges or bumps in the support layer can lead to tendon damage. A bandage that is too loose will fall down, creating folds and bulges. After a vetwrap layer to hold the support wrap in place, the ends of the bandage may be taped to the limb to minimize contamination from either the top or the bottom openings.

After granulation tissue fills the defect, bandaging of lower limb wounds is generally contraindicated. Exceptions include wounds  near the ground or in very contaminated environments. Occasionally horses will chew at the wounds; these wounds may need bandaging for protection (and additional methods to prevent chewing may still be required).

Many horse owners will want to apply various solutions to the wound to prevent proud flesh (exuberant granulation tissue) formation. While most of these agents do control proud flesh, they also damage the new epithelial cells. If needed, corticosteroid cream can be applied in a light layer once weekly.

Bandaging – upper limb wounds

Bandages can be sutured over the wound if needed (stent bandage). Circular loops of suture are placed adjacent to the wound and a fresh towel or pad held in place by “laces” threaded through the loops.

 

Key Takeaways

The main steps for wound management are

  • cleaning
  • sharp debridement
  • closure or management for second intention healing
  • restrict activity

NSAIDs are helpful. Antibiotics are typically not needed or are only needed until granulation tissue develops. Corticosteroid may be used weekly to control granulation tissue.

Horses are not always good patients. Warn your clients that any repair can fall apart – generally in 2-3 days.

Most limb wounds will need to heal by second intention. This means lots of bandage changes and prolonged stall rest. Topical antibiotics help everyone feel better for the first 5 days.

Resources

Topical Wound Medications, VCNA Vol.34(3), pp.485-498, 2018

Equine Practice on Wound Management Wound Cleansing and Hygiene, VCNA Vol.34(3), pp.473-484, 2018

Things You Should and Should Not Put on a Horse’s Wound, The Horse, 2016

Wound Care in Horses, VCNA Vol.28(1), pp.83-100, 2012

License

Icon for the Creative Commons Attribution-NonCommercial 4.0 International License

Large Animal Surgery - Supplemental Notes by Erin Malone, DVM, PhD; Elaine Norton, DVM PhD; Erica Dobbs, DVM; and Ashley Ezzo, DVM is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.