A burn is an injury in which the tissue proteins are destroyed by a process called coagulation. The large majority of burns are caused by heat.
Heat, as earlier stated, is the commonest cause of burns. The burn may occur from a flame, hot metal or hot liquid. Scald is a term used for superficial burns caused by hot water (or other liquid). Burns are more severe if the causative agent is hotter, and is in contact for a longer time.
may also occur from chemicals such as strong acids or
alkalis, radiation, electricity and extreme cold.
Heat causes damage to the skin. The chemical change in skin tissues is a coagulation of the proteins. Depending on the temperature and duration of contact the burn in its depth may vary from superficial to deep, and in size may vary from large or small.
Depth: the burn wound may involve only the epidermis, the dermis or even the underlying tissue including muscle and bone. Depending on the depth burns are classified into first, second and third degree burns. First degree burns involve only the epidermis. Second degree burns involve part, but not the whole of the dermis. In third degree burns, the entire dermis is burnt. Third degree burns are also known as deep burns or full thickness burns (1o and 2o burns are partial thickness burns, or superficial burns).
Area: The burnt area may be small or large. The extent of burn is usually expressed as a percent of total body surface area. A 50% burn implies that half the body skin area has been burnt. 1o burns are so superficial that they quickly heal without scarring. 2o burns heal mainly from the basal layer of the dermis, because parts of this basal layer survive the burn injury. There is some scarring, the amount of which varies. 3o burns are those in which the entire dermis is burnt, including the sweat glands and hair follicles. Nerves are also burnt, therefore pain is less in third degree burns than in second degree burns. Healing is from the edges of the burn wound, not from the residual dermis (as in second degree burns). It takes a long time, and is accompanied by a lot of scarring.
Normally the skin regulates body water, regulates temperature and protects against bacteria. The burn wound is an area where the skin does not function. Water, electrolytes (such as sodium, potassium and chloride) and proteins are lost at a very high rate from a burn wound. With the excessive loss of water, temperature falls. The burnt tissues offer bacteria a good opportunity for colonization. In small burns, the body can easily cope with the water loss, temperature fall and mild infection. However in large burn areas (over 10% body surface area) these complications may become life threatening, and need attention.
The burnt area becomes inflamed, and generates edema. The eschar that forms in a 3o burn is not elastic, unlike normal skin. If there is a circumferential burn in a limb, the pressure within the tissues under a 3o burn rises markedly because of edema, and may become so high that the blood supply to the limb stops, resulting gangrene of the limb distal to the burn.
Bacteria infecting the eschar release enzymes that collect under the eschar and separate it from the underlying tissues, usually in the 3rd week after the burn. This is known as spontaneous separation of the eschar, and occurs without any blood loss. Unfortunately, in this period the bacteria also release toxins, which cause great harm to the host.
Clinically, first degree burns present with redness, and some pain. They are usually called by short exposures to mild heat, such as hot liquids . Left alone the injuries recover. Second degree burns are associated with moderate to severe pain. Second degree burns usually present with blisters. Deeper 2o burns manifest as large whitish ulcerated areas. A pinprick will elicit pain sensation. Third degree burns present with an eschar, which is the parchment like tissue that is present at the burns area. The eschar is brownish in colour, and there is no sensation on pricking with a pin. Initially the eschar is adherent to the underlying tissues.
Some patients will have inhaled smoke during the burn event, with harmful consequences for the lungs. This is called smoke inhalational syndrome, and can result in lung failure.
The extent of burn is calculated by the rule of nines. The head (including neck), anterior chest, posterior chest, anterior abdomen, posterior abdomen, left upper limb, right upper limb, left thigh, left leg, right thigh and right leg each account for 9% of the body surface area. The perineum accounts for 1%. In children the proportions change, since the head has a much larger size as compared to the rest of the body.
First aid: The fire is extinguished with blankets, and burning clothes are removed. In minor burns it helps to wash the wound with water. Washing is not advisable for large area burns (over half the body surface area) as this may cause a fall in temperature.
Care of minor burn: In small burns the problems are of pain and local infection. The wound should be washed with cool water and dressed with an antibacterial ointment such as povidone iodine, framycetin, or silver sulfadiazine. The dressing must not stick to the wound, and paraffin soaked gauze is recommended. Dressings are changed as often as possible, usually daily. Blisters heal best if left alone, but they are painful and cumbersome. The fluid in them may be aspirated under strict asepsis, but it should be remembered that aspiration can result in infection. Blister skin protects the underlying ulcer, and promotes healing. However removal of blister skin, followed by regular dressings, minimizes the chance of infection. Overall, it is probably best to aspirate the blister and dress daily, preferably under cover of a systemic antibiotic such as cloxacillin. Burnt hands should be elevated to minimize edema. Painkillers, antihistaminics (for itching) should be given as required. Small but deep burns over joints can cause contractures, and may require grafting early.
Management of major burns needs to be done in hospitals in burn care centers. Intensive monitoring is needed. In large area burns the complications are fluid loss, infection, protein loss, hypothermia (abnormally low temperature), eschar effects as mentioned above, stress ulceration, smoke inhalation syndrome, risk of tetanus, and long term complications such as contractures and disfigurement.
Since the patient loses fluid at a rate directly proportional to the burnt area, formulae have been devised to calculate the amount of fluid required in a patient with burn. These formulae go by the names Brooke formula and Parkland formula, which allow 4 ml of fluid x body weight in kg x % burn surface area in one day.
Infection is controlled by dressings and antibiotics. Antibacterial agents used for dressing should be selected with care.
The burnt area loses proteins in large quantities. Management is by administration of a high protein, high calorie diet. Patients who cannot take enough may need to be artificially fed by a stomach tube or intravenously.
A circumferential eschar may block the blood supply to the limb distal to the burn. To prevent this, the constricting eschar should be divided by an escharotomy. After a few days the eschar should be removed altogether by an operation called escharectomy.
Anti-ulcer medicines should be given to prevent peptic ulcers. Smoke inhalation syndrome if present will need oxygen and perhaps artificial respiration. To prevent tetanus, an injection of tetanus toxoid should be given. Contractures and disfigurement are prevented by suitably timed plastic surgery.
Other types of burns
Other types of burns are chemical burns, radiation burns and electrical burns. Extreme cold may also cause coagulation necrosis, or cold burn.
Chemical burns may be caused by strong acid or alkali. First aid is by copious irrigation of the injured area by water (not by a neutralizing chemical).
Electric burns are caused by high voltage electric currents or by lightning. There is a point of entry and a point of exit. Current passes very easily through blood, nerve and muscle. The vessels develop clots leading to gangrene of some parts of the body. Muscles may get damaged. The heart may become severely irregular. Treatment is symptomatic. Gangrenous tissue should be removed.
Cold burns. Cold burns usually occur in alcoholics exposed to extreme cold.
Sood, MBBS (AIIMS), MS (AIIMS), MAMS, is a
practising surgeon attached to Dharamshila Cancer
Hospital, Sir Ganga Ram Hospital and to Noida Medicare
Center. Formerly Professor of Surgery, Himalayan
Institute of Medical Sciences, Dehradun, Dr Sood has a
special interest in gastrointestinal surgery. He has had
an active academic career, has published several papers
in national and international journals, and is the Editor
(with Dr Anurag Krishna) of a widely acclaimed book
titled Surgical Diseases in Tropical Countries.
Last revised: May 11, 2000