Burn injuries are uncommon in horses. Barn fires are the most common reason and can result in extensive areas of injury to multiple animals so when encountered the extent of the burn injuries may be remarkable. This combination of rare but severe when encountered makes for difficult evaluation and treatment for the veterinarian. Little research is done with horses and burns but much of what we know about human burns can be applied to horses. The size and temperament of the horse does limit our options however. This article discusses assessing the severity of a burn, first aid, treatment, and prognosis.

Prior to examination of the wound a complete exam of the horse should be done with an emphasis on evaluating the cardiovascular and lung status. Early and aggressive first aid is important as it may have a large effect on the severity of the burn. Exam criteria used to evaluate burns include:

• Cardiovascular values
• Respiratory values and auscultation of lungs
• Body temperature
• Appearance of wound
  • redness (erythema), swelling (edema) and pain
  • vesicle (blister) formation,
  • eschar formation,
  • touch sensation
  • presence of infection if wound is several days old

With severe burns, shock can occur due to decreased output from the heart and loss of fluid through the damaged skin. Smoke inhalation may result in fluid forming in the lungs (pulmonary edema). Shock and pulmonary edema does not seem to be as big a problem in horses as it does in humans but has been recorded. Other secondary systemic alterations seen are fluid, electrolyte, protein loss, anemia, impaired immune system, and increased basil metabolic rate.

The damage done will depend on the amount of heat, length of time exposed, and the first aid received. For example, tissue is slow to heat and slow to cool so damage continues after the heat source is removed and before the tissue cools. Applying cold can greatly reduce the severity of a burn. Burns cannot always be accurately accessed just after the injury. Both the area and the depth may be underestimated on the first evaluation and it may require up to 48 hours before the extent of the initial injury is known. Burns are classified by how deep the injury goes. The deeper the tissue is injured, the more difficult the treatment and the poorer is the prognoses. There are three basic classifications but it is important to realize that all of them may be present after a severe or extensive burn.

• Superficial: The skin is red, painful, and has moderate swelling. The swelling is a thickening of the skin from edema and so pits. Redness, swelling, and pain within the burn wound are favorable signs because they indicate that viable tissue remains. However, pain is the least reliable indicator in determining wound depth. The wounds always need to be reevaluated for severity for a few days as some changes take time to develop. Often some time must elapse before changes occur that are sufficient for accurate evaluation of burn severity.
• Partial Thickness: Vesicles and blisters form, the skin is red around the blisters, painful, and markedly swollen with remarkable subcutaneous edema and inflammation. Though not life threatening these can be extremely painful.
• Full Thickness: Full thickness burns penetrate completely through the dermis and damage the underlying structures. Consequently, cutaneous sensation is lost with fill-thickness burns. Though the skin may still be present, in time it will slough.

The order of physiological events that explains this progression of events is: thermal injury > vasoactive amines > vasculature dilation + increase in capillary permeability > Fluid, protein, and inflammatory cells exude > local swelling and edema > vascular sludging, thrombosis > dermal ischemia > death of dermal cells > thromboxane release > progressive dermal ischemia, resulting in advancing cell injury and death. NSAID's and aloe vera reverse and prevent further cell death.

Exposure of damage tissues along with decreased immune function predisposes burn wounds to local infection and may lead to septicemia. Bacteria frequently isolated from burn wounds include Pseudomonas aeruginosa. Staphylococcus aureus, Escherichia coli, P-hemolytic Streptococcus, nonhemolytic Streptococcus, Klebsiella pneumoniae, Proteus spp? Clostridium spp., and Candida.