Luis H. Tello, DVM, MS
Small animal patients can suffer different sources of burn lesions: electrical, chemicals, direct heat, fire, fireworks, etc. A common cause of burn in small animals is the use of electrical heating pads during surgery or in cage hospital management.
Burn injuries are extremely complex, with compromise of respiratory, cardiovascular, dermatological systems, and require a proper understanding and management of physiology, endocrinology, nutrition and immunology status of the patients, to give them appropriate treatment.
Burns affect primarily the skin, and the degrees of injury are related to the depth and extension surface affected. The skin have many different roles in the normal physiology of the body: is the primary barrier against invasive infection, the skin help to maintain the body temperature controlling the evaporation of fluids, the skin adapts to aggressions or changes in the environment like pain, cold and heat. All these functions are impaired in burned animals and have been related as secondary cause of death.
Affected surface can be approach by burned body segments:
Each forelimb means 9% each rear limb means 18%, head and neck 9%, Trunk and abdomen 18% each one of the total body surface.
Burn depth has been classified in degrees of injury:
Superficial or first degree involves the epidermis layer, Partial-thickness or second degree involves the epidermis and mid to deep amount of dermis, and the full-thickness or third degree there is complete destruction of the skin and compromise structures of the subcutaneous.
The initial assessment should start with de general physical condition, systemic compromise, amount of body and surface affected, plus degree of local injury. If the lost of skin are larger enough, euthanasia can be recommended.
Animals involved in fires have respiratory injury due to the inhalation of air heated to a temperature higher than 150C°, results in burns into the mouth, oropharynx, and upper airway. The main cause of death on these patients is smoke inhalation associated to the fall of oxygen concentration in the ambient, due to the carbon monoxide and dioxide during combustion.
Animals affected by smoke inhalation should be placed on 100% oxygen early after arrive to ICU. Endotracheal intubation is necessary if patient show respiratory distress. Pulse oximetry cannot evaluate the severity of hypoxia because his lack of capability to differentiate between oxygenated hemoglobin and carboxyhemoglobin.
The initial therapy is oriented to relief the pain with cold direct application in the burn area: chilly water, soak towels, cold tap water are good alternatives. Oxymorphine alone or combined with Acetylpromazine in neuroleptoanalgesia is indicated to pain control in dogs. Cats can be treated with Diazepam plus Ketamine.
Oxygen 100-150 ml/Kg/ per minute should be initiated, as soon as possible and a central catheter into jugular vein should be placed. Give fluid replacement at 4 ml/Kg per hour in dogs and 2 ml/Kg per hour in cats. Isotonic balanced electrolyte solution like Lactated Ringer´s or normal Saline is the first choice. Free glucose fluids must be avoided because hyperglycemia and glucosuria will occur after deep burns.
Potassium levels should be monitored because during the first 24 hours it will be a rise with severe hiperkalemia associated to cells destruction into the burned tissues. Solutions with contents of 4-5 mEq/L of potassium are recommended during this phase.
Check out serum protein levels, urine production, hematocrit level, hemoglobin, electrolytes and blood gases. If total protein drops below 3 gm/dl, fresh plasma or colloids should be added. Acidosis can be corrected with Sodium bicarbonate 5 mEq/Kg of body weight may be given every hour or 30 minutes.
If hematocrit falls below 20% or, hemoglobin falls below 7 gm/dl, whole blood or washed red blood cells must be added to the treatment. Hct above 30% is the goal.
After start analgesia treatment, the burn wound can be washed with antiseptic solutions as povidone iodine or chlorhexidine. Necrotic tissues, foreign material and debris must be removed.
Burn wounds of first or second degree should be topically treated with antibiotic medication and bandaged. With third degree burns, eschar must be removed soon and in a daily frequency. That is a very painful procedure, so anesthesia or proper analgesia should be considered. Eschar must be removed to show healthy underlying granulation tissue.
Systemic antibiotics do note penetrate eschar, so topical therapy is always indicated with antibiotic ointments and creams. Gentamycin, Polymyxin, Neomycin, and bacitracin are very effective against the contaminant flora in burn wounds, as well as fluoroquinidones.
Last reports with Aloe vera shows certain antiprostaglandin effects that can help to maintain normal dermal vasculature.