Management Of Thermal Burns

By | 2012-10-23

Skin is usually quite slow to absorb heat; as a result, its dissipation also takes much longer than might be expected. Therefore the skin is slow to burn, and the burning effects may continue for some time after the cause has been removed. Furthermore, burn injuries heal very slowly, even in sites where healing is normally good. Therefore the attending veterinarian and the owner must be willing and able to embark upon the process of healing (). The long course inevitably also means a high cost.

All burns should be treated immediately by the application of cold running water, which should be applied for at least 15 minutes. This will reduce the heat retention and limit the consequent necrosis. A protective, water-soluble emollient antibacterial cream should be applied to the burn area. Oil- or fat-based ointments should be avoided. Silver sulfadiazine (Silvadene) is a very useful topical medication for superficial or partial thickness burns over limited areas.

The metabolic status of the horse must be carefully assessed and supportive measures applied as necessary. These include fluid therapy and, if necessary, an immediate plasma transfusion to ensure that shock is controlled. The loss of plasma is maximal in the first 12 to 24 hours. In all cases, large volumes of intravenous fluid therapy are a useful first emergency measure. This applies particularly to the more severe burns (full-thickness over 5% or more of the body). If the animal is already in a state of shock, aggressive antishock therapy must be instituted immediately. This course of action may include large volumes of balanced electrolyte solutions (e.g., Hartman’s solution or lactated Ringer’s or even hypertonic [7%] saline). A helpful rule of thumb is that for each percentage body surface involved, 3 to 4 ml/kg body weight should be administered. Fluids should not be sustained if hydration is adequate because it might add to the secondary edema, particularly within the lungs.

Plasma protein estimation may identify falling total protein with albumin loss. Good-quality fresh or preserved plasma will be useful; 1 L of plasma will raise the total protein by about 0.2 g/L in a 450-kg horse. The total volume of plasma required for severe burn cases can be up to 40 L or more over 2 to 3 days. This can usefully be sustained at a low rate for as long as required.

Pain relief in the form of flunixin meglumine (1 mg/kg IV q24h) or phenylbutazone (2 mg/kg ql2h) is essential. Pain is often more severe in the more superficial types of burn. Full-thickness burns may not be very painful, but the metabolic consequences of this type of burn are usually more severe.

The topical use of dilute chlorhexidine solution in saline is controversial. Controlling infection is clearly meritorious but may be better performed simply by irrigation. However, burns are particularly liable to infection. Therefore topical water-soluble antibiotic creams may be advisable. Blisters should be left alone for at least 36 to 48 hours. No merit exists in trying to burst or drain these blisters.

Bandaging may be possible in some cases. In such a case, hydrogel should be applied liberally to the site. Burns are usually highly exudative because of the deficit in skin and the loss of cutaneous lipid. Thus an absorbent dressing should be applied. Bandages must be firm enough to provide support without slippage but loose enough as to limit any further vascular compromise. The dressing must not stick to the wound site.

Full-thickness burns must be covered immediately with a protective fluid proof dressing. In an emergency a clear plastic kitchen wrapping can be useful. Ideally, a hydro-gel should also be applied directly to the wound site from the outset.

After 24 to 36 hours, the wound can be cleaned and all damaged tissue removed. The clinician should expect further necrosis to develop over the following few days or weeks. At this stage, all hair in the affected area can usefully be clipped. This prevents matting and reduces pain.

Dressings should be replaced frequently over the first few days, and any necrotic tissue should be removed. A calcium alginate dressing (e.g., Algiderm) is a useful absorptive dressing that will maintain moist healing conditions at the site. Once healing is underway, the dressings can be left for up to 3 to 4 days, provided that no complications develop. An eschar should be left in situ until natural sloughing occurs. While it remains in situ it provides an effective biologic cover and protection for the underlying tissues. An overlying moist wound dressing (e.g., a hydrogel [Tegagel]) can sometimes reduce the time taken for the eschar to separate and may also encourage contraction of the healing edges of the wound.

The metabolic status of the horse must be regularly assessed and must include full hematologic profiles for protein analysis and electrolyte status. Hyperkalemia is a common consequence, and seriously burnt horses may show hemoglobinuria. Progressive anemia is a serious potential effect of extensive burns and requires attention as soon as it is recognized. Usually it is caused by a combination of intravascular hemolysis and bone marrow suppression.

The nutritional status of the horse is critical to its recovery. Almost all serious burn cases are in a negative protein balance (i.e., they are losing more than they are absorbing) and have a very much raised energy requirement. The early stages may require parenteral nutritional support, but if the horse will eat, gradual addition of vegetable oil into a high-quality ration (possibly of alfalfa hay) can be helpful.

In cases of extensive skin deficits, skin grafting should be considered at an early stage — as soon as the granulation tissue is healthy enough to accept a graft. Grafting is unhelpful until all necrotic tissue is removed and the bed of granulation tissue is healthy. Split-thickness, mesh grafts in single sheets or postage-stamp format can be used effectively. Cosmetic grafting with extension flaps, tube grafts, and so on are all techniques that can be applied to the healing of burn injuries of all types. Artificial skin substitutes (e.g., Integra) may be used to protect the exposed tissues and reduce the extent of plasma exudation.