Burns, Thermal

Article Author:
Timothy Schaefer
Article Editor:
Shruti Tannan
Updated:
10/27/2018 12:31:26 PM
PubMed Link:
Burns, Thermal

Introduction

Thermal burns are skin injuries caused by excessive heat, typically from contact with hot surfaces, hot liquids, steam, or flame. Most burns are minor and can be treated as outpatients or at local hospitals. Approximately 6.5% of all burned patients are treated in specialized burn centers. The decision to transfer and treat at burn centers is based on the extent of body surface area burned, the depth of the burns and individual patient characteristics such as age, other injuries or other medical problems.

Etiology

Thermal burns are the most common type of burn injuries, making up about 86% of the burned patients requiring burn center admission. 

Epidemiology

Approximately 450,000 patients received treatment for burns annually, and about 30,000 are admitted to burn centers. About 86% of burns are thermal burns (43% from fire/flame, 34% from scalds, 9% from hot objects), 4% electrical burns, 3% chemical burns and 7% are other types of burns. Annually, approximately 3400 patients die from burns or related complications such as smoke inhalation, carbon monoxide or cyanide poisoning, organ failure or infection. Roughly 72% of these deaths occur from residential fires. Burns represent the fourth leading cause of trauma deaths and the second leading cause of accidental deaths in children ages one to four. The good news is that the overall survival rate for all types of burns is about 97% and deaths from burns have declined by about 75% from the 1960s.

Pathophysiology

The skin is the largest organ of the body making up about 16% of a person’s weight. The main skin functions are protection (infection, temperature changes, physical forces, chemicals, etc., the), body temperature regulation, preventing fluid loss and cosmetic/identity. The skin is made of two primary l; the thinner outer layer called the epidermis and the deeper thicker layer called the dermis. There are various other structures within the skin like hair follicles, sebaceous glands, sweat glands, capillaries and nerve endings.

Thermal burns cause both local injuries and if severe (> 20% of body surface area), a systemic response. The local injuries can be roughly separated into 3 zones of injury analogous to a circular target pattern. The innermost injury is the zone of coagulation or necrosis representing the area of irreversible cell death. Surrounding this is the zone of ischemia or stasis representing an area of decreased circulation and an area at increased risk of progression to necrosis due to hypoperfusion or infection. The outermost area is the zone of hyperemia representing an area of reversible vasodilation and an area that usually returns to normal. In clinical practice, burns are dynamic injuries that may progress over hours to days, making it difficult to accurately determine the various zones during the early course of the injury.

Large burns (>20% body surface area) also cause a systemic response from the release of inflammatory and vasoactive mediators. Fluid loss locally at the burn site, fluid shifts systemically, plus decreased cardiac output and increased vascular resistance, can all lead to marked hypovolemia and hypoperfusion called “burn shock.”  This can be managed with aggressive fluid resuscitation and is discussed in the Burn, Resuscitation and Management chapter.

History and Physical

Most burns are small and are classified as minor burns with the main symptom being a pain. These burns will need only local burn wound care and pain control. If the patient has extensive and deep burns, then they may be classified as severe burns and could be approached like other trauma patients (See Burns, Resuscitation, and Management for discussion of severe burns). If the patient does not have severe burns, then the history and physical examination can proceed as usual. Key parts of the history to include are the type of burn (thermal, electrical, chemical, radiation), the possibility of associated inhalation injury (e.g. trapped in an enclosed space) and the possibility of other injuries (e.g. explosion or jumped to escape a fire).

During the physical exam, special attention should be placed on the airway and breathing looking for oral burns, facial burns, soot in the nose or mouth, coughing, wheezing or labored breathing. Also, look for signs of injury other than the burns. Finally, the burns are the focus of the skin exam and the key features to assess are the extent of the burns, expressed as percent of total body surface area burned (% TBSA), and the depth of the burns, expressed as superficial (or first-degree), partial thickness (or second-degree) or full thickness (or third-degree).

If the burn injury only involves the epidermis, it is classified as a superficial or first-degree burn and does not cause any significant impairment of normal skin function. If the injury extends into the dermis, it is classified as a partial thickness or second-degree burn. Partial thickness burns may disrupt skin functions such as protection from infection, thermal regulation, prevention of fluid loss, and sensation. If the injury extends through both layers, this is classified as full thickness or third-degree burns, and normal skin functions are lost.

Superficial (or First Degree) burns are warm, painful, red, soft, usually, do not blister and will blanch when touched. A typical example is a sunburn. Partial thickness (or Second Degree) burns can vary but are very painful, red, blistered, moist, soft and will blanch when touched.  Examples include burns from hot surfaces, hot liquids, or flames. Full thickness (or Third Degree) burns have little or no pain, can be white, brown, or charred and feel firm and leathery when touched and will not blanch. Examples include burns from flames, hot oils, or superheated steam.

Evaluation

The American Burn Association’s criteria can help differentiate burns as minor, moderate or severe based on the extent of skin injured, the depth of the burns, age of the patient (<10 or >50 y/o),  associated medical conditions, associated injuries such as smoke inhalation or other trauma, or burns involving particular areas of the body such as the hands, feet, face, ears, nose, or genitalia (See also Burns, Evaluation and Management for more details regarding determining depth and extent of burns).

Treatment / Management

The first step to is to immediately stop the burning process by removing burning and hot items from skin contact. Small areas of burn can be cooled with liquids like tap water or saline solution. If the patient has larger burns, be cautious of extensive cooling as this could lead to hypothermia. Superficial burns need little more than over-the-counter pain medicine, topical analgesics, or topical aloe vera. Partial thickness and full thickness burns are treated with cleansing, topical antibiotic ointments or occlusive dressings, pain medications, and tetanus booster if needed. Patients with severe burn will require fluid resuscitation, oxygen, cardiac monitoring, nasogastric tube, Foley catheter, IV pain medication, tetanus booster and transfer to a burn center. If patients are being transferred to a burn center, simply cleaning and covering the burns without topical creams or ointments is all that is usually needed. It’s best to contact the burn center for instructions.

Debate continues over the best way to treat blisters. Large blisters, tense blister, and blister crossing joints are debrided while small blisters and blisters involving the palms or soles are left intact.

One method of treating partial thickness burns is to cover them with topical antibiotic ointments, like bacitracin or triple-antibiotic ointment, and then apply a simple absorbent dressing. The ointment can be spread on the dressing like peanut butter on bread, then placed on the burn. Dressings are changed once or twice a day and may take 1-2 weeks to heal. Silver sulfadiazine has historically been a commonly used topical antibiotic cream but is falling out of favor with growing evidence it can delay healing. The other method of burn wound management is to apply a specialized occlusive burn dressing like Mepilex Ag, Aquacel Ag, or Duoderm to the burn and leave this in place for about one week.

Because burns are dynamic injuries, they are difficult to accurately assess on the initial exam. Patients with burns should be reexamined in several days to reassess both the extent and depth of the burns.