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CHAPTER 33

Burns

Peter Nthumba
Renata Fabia

Introduction central zone of tissue coagulation composed of irreversibly injured
A burn wound is a wound resulting from physical heat (thermal), tissue, and both are surrounded by the zone of hyperaemia. Increased
chemical agents, or electric current applied to any part of the body. vascular permeability in the zone of hyperaemia/inflammation causes
Burn injuries are common, complex injuries of cutaneous and under- transudation of fluid into the interstitial space, leading to oedema. The
lying structures that are particularly difficult to manage in Africa due extravasation continues for 24–48 hours. In extensive burns, this may
to inadequacies in infrastructure, resources, and staff. Factors such lead to hypovolaemia and shock, if untreated.
as poverty, illiteracy, urban migration, and the development of slums
and shanty towns contribute to the high incidence of burn injuries in
African children.
Burn injuries produce significant morbidity and mortality,
particularly in children younger than 5 years of age. Prevention of burn
injuries is of great importance because the consequences of burn injury
in a child are scars that affect the child’s life in a variety of ways.
Demographics
Although burn injuries are quite common, exact statistics are not Figure 33.1: The histological effect of burn injury at the site of injury.
available. Extrapolation from population-based studies suggests that
the incidence of hospitalised paediatric burn patients is highest in
Africa and lowest in the Americas, Europe, the Middle East, and Asia. Appropriate cooling, fluid resuscitation, and maintenance of tissue
However, hospital-based data vastly underestimate the true incidence of perfusion may reverse the changes in the zone of stasis, allowing it to
burn injuries because many children are seen in outpatient settings with revert to normal. If not properly managed, continued tissue injury in
minimal documentation. this region may lead to an increase in the clinically apparent area of
Children younger than 5 years of age are at greatest risk of burn. necrosis of the zone of coagulation.
Children younger than 2 years of age have more than twice the Oedema
mortality rate of older children and adults with equivalent injuries. Increased capillary permeability in injured tissue, protein leakage, and
Aetiology the resultant hypoproteinaemia lead to increased osmotic pressure in
burnt tissue, hence the oedema. In general, oedema is maximal at 24–48
Burn injuries may result from hot liquids (scalds), hot objects, flames,
hours, resolving in 3 to 4 days. However, in children with large burn
explosives, chemicals, friction, and electrical current. Scald burns
wounds, the inflammatory response and tissue oedema may be signifi-
are the most common, contributing up to 80% of burn injuries in
cantly prolonged.
some series. In comparison, in the United States, the leading burn
injury mechanisms among children younger than 4 years of age are also Hypermetabolism
scalds, followed by hot objects and outdoor fires. Kerosene is the most The basal metabolic rate may increase up to 200 times, leading to a
common source of flame burns in Africa. hypermetabolic phase associated with increased levels of catechol-
Most paediatric burn injuries in Africa occur in the home amines and catabolic hormones. Hypermetabolism slows down with
environment, often while the child is under the care of a nonparental treatment and resolves upon wound closure. The hypermetabolic
caregiver. In some cases, burn injury is a manifestation of child abuse. response leads to increases in oxygen consumption, basal metabolic
Nonaccidental burns are also seen in some cultures where therapeutic rate, urinary oxygen excretion, lipolysis, protein catabolism, and
burns are practiced as a means of treating febrile convulsions and decreased synthesis, along with weight loss, that are directly propor-
epilepsy, based on the belief that heat will terminate the convulsion. tional to the size of the burn. Early enteral feeding may attenuate the
Bilateral symmetrical burn of the feet from the immersion of both feet hypermetabolic response.
in hot water is a characteristic pattern in such therapeutic burns. Many ongoing studies are focused on modulation of catecholamines
Pathophysiology in order to decrease oxygen demand, cardiac rate, and energy
expenditure. Some of the promising agents include beta adrenergic
The depth of a burn injury depends on the temperature and duration of blockers, insulin, and the anabolic steroid oxandrolone.
exposure to the heat source as well as the patient’s age. For example,
the immersion time needed to induce a burn injury following exposure Classification of Burns
to water heated to 54°C is 30 seconds in an adult, 10 seconds in a child, Burn injuries are classified into first- (superficial thickness), second-
and less than 5 seconds in an infant. (partial thickness), and third-degree (full thickness) burns (Table 33.1).
The initial local effect of a burn injury is divided into three histological Second-degree burns are further subclassified into superficial and deep
zones (Figure 33.1). An intermediate zone of stasis surrounds a second-degree burns.