Trauma part 4: Burns

In the final article in our series on trauma, Omar Mukhtar and Kirsten Jones explain how to assess and manage burns

Burns are common; they account for more than 12 000 admissions to hospital each year in England and Wales alone. Only a fraction of this number is seen in parts of Africa and Asia. Despite the geographical variation in prevalance, the situations in which burns occur are the same everywhere--about two thirds take place in the home, and most of the rest occur in the workplace. More importantly, most burns are preventable.

What is a burn?

A burn is coagulative destruction of the skin; wounds are different because the epidermis (and sometimes the dermis) is breached. Four factors can cause burns (box 1), and burns are classed as either partial thickness (first degree or second degree) or full thickness (third degree).

Partial thickness burns, both superficial and deep, heal spontaneously without a skin graft because various elements of the epidermis are undamaged. If only the superficial epidermis is affected--that is, the underlying germinal layer is intact and tissue is minimally damaged with blistering and erythema (due to capillary dilatation)--the burn heals in days and leaves no scars.

Deep partial thickness burns extend beyond the germinal layer, and only the sweat glands and hair follicles are undamaged. New skin will form from adjacent areas of intact epidermis and from sweat glands and hair follicles. Blistering and slough are visible and scarring is inevitable, especially if secondary infection occurs. In contrast to full thickness burns, deep partial thickness burns have intact pinprick sensation and usually heal in two to three weeks.

In full thickness burns, all layers of the skin are destroyed, and in severe cases underlying structures may be damaged. Charring is usually evident, and in severe cases the skin is white and leathery. If the burn was left to heal, fibrous tissue would cause contractures to develop: skin grafting is needed to minimise scarring and deformities in almost all cases.

Assessment

As with all trauma, assessment should initially consider resuscitation; airways, breathing, and circulation. Specific aspects to consider include:

Airway burns--hoarseness, stridor, dysphagia, direct burns to the face or oropharynx, and singeing of nasal hair indicate that the airway may be damaged. The resulting oedema may make intubation difficult; ask an anaesthetist for help early on.

Spinal injuries--have a high index of suspicion, particularly in the case of blast injuries or in patients who have jumped from burning buildings.

Breathing difficulties--full thickness circumferential burns of the chest--"eschar"--may limit chest expansion.

Circulatory problems--hypovolaemic shock is a feature of severe burns and needs immediate fluid resuscitation.

History

If resuscitation is not required, a history is the first point of assessment. Establish the environment in which the burn took place--this allows you to understand the precise nature of the insult and evaluate any additional risks. One important risk to consider is exposure to noxious gases--for example, burning polyvinylchloride releases hydrogen cyanide, and fires in confined spaces can cause poisoning from carbon monoxide. You should also determine whether the patient has any relevant medical history and current tetanus status.

Examination

When you examine a patient's burns, it is important to assess the depth and the extent of the burns; the extent is particularly important for resuscitating fluids. The extent of a burn, the area of the surface of the affected skin, can be approximated in many ways. The easiest to remember is Wallace's rule of nines, which applies to only adults (see figure). Other methods include using Lund and Browder charts (available in most emergency departments) and evaluating the surface area of the burn on the basis that a patient's palm is about 1% of their total body area.

Assessment of depth focuses on whether the burn is either partial or full thickness. This can be established by a complete examination of the affected area looking specifically for the features already described. Distinguishing a deep partial thickness burn from a full thickness burn in the acute setting can be difficult, but this may not influence initial management.

Management

Minor burns do not routinely require admission; the aim is to prevent dehydration and suprainfection (box 2). Partial thickness burns tend to blister. Deroofing the blister--removing the fluid by removing the entire superficial covering--used to be common. Avoid deroofing as it increases the risk of infection; instead, aspirate the fluid with a syringe. Apply a non-stick dressing, and advise the patient to have the dressing changed every 24 or 48 hours at his or her local surgery. Fluid may reaccumulate, and emphasising the importance of patients changing their dressings is essential. The precise nature of the dressing depends on local preferences and availability--seek the advice of a senior nurse.

Be aware that if a partial thickness burn fails to heal after 21 days, the burn is likely to be full thickness and needs skin grafts; refer the patient to a plastic surgeon. Similarly, full thickness burns should be left uncovered and the patient referred to a specialist as an urgent outpatient.

Fluids

Burns which affect 15% of the adult body (or 10% of a child's body), irrespective of depth, are associated with sufficient fluid loss to place the patient at risk of hypovolaemic shock. Most fluid is lost in the first 12 hours, but substantial losses may continue up to 36 hours after the incident. The fluid lost is similar in composition to plasma--the primary replacement fluid is succinylated gelatin (a plasma substitute). Additional fluid can be given as isotonic electrolyte solutions such as sodium lactate intravenous solution.

Fluid replacement should be calculated using a well tried formula, such as that of Muir and Barclay. The formula gives the volume of a ration of fluid; three rations of fluid should be given in the first 12 hours, two during the second 12 hours; and one in the final 12 hours (box 3). Fluid balance must be monitored by pulse, blood pressure, and urine output; catheterisation is usually necessary in an extensively burned patient.

For analgesia, small doses of intravenous morphine should be given often to the patient and titrated to response. As always when a patient is taking morphine, an anti-emetic, usually intravenous cyclizine, is important.

Regular swabs should be taken from the burn, but prophylactic antibiotics are not required. Suprainfection, however, should be treated on the basis of culture and sensitivity results. Organisms commonly causing sepsis include staphylococci, streptococci, and pseudomonas.

Skin grafts

Skin grafts are either free grafts or pedicle flaps. For a free graft, tissue is taken from a part of the body and grafted on somewhere else; the tissue loses its original blood supply and is entirely dependent on the good vascular perfusion of the new area. In contrast, pedicle flaps retain much of their blood supply from the source of the graft. Most patients with burns need a free graft. The thickness of the graft varies according to the thickness of the burn.

Managing burns in special sites

In deep circumferential burns of the limb or chest, burnt skin may occlude the blood supply to the extremities or limit respiration. This must be recognised and treated rapidly; divide the skin along the length of the limb or in a criss cross pattern on the chest wall.

Burns around the eye rapidly result in massive oedema: examine the eye before the palpable fissures close. If the eyelids have been destroyed, the eye must be bathed with artificial tears and the eyelids restored by plastic surgery to prevent corneal scarring.

Omar Mukhtar, final year medical student, University of Bristol
Email: studentdoctor@hotmail.com

Kirsten Jones, consultant in emergency medicine, Frenchay Hospital, Bristol


studentBMJ 2003;11:219-262 July ISSN 0966-6494