Burns

Thermal burns • Significant thermal burns occur in 0.5% of the population every year. • Thermal burns tend to occur in: • The young • The old • The unlucky

Zones of injury Jackson has classified thermal burns into three zones of injury. 1 An inner zone of coagulative necrosis 2 An intermediate zone of stasis 3 An outer zone of hyperaemia.

Pathophysiology of burn injury Local effects • Inflammatory mediators are released from: • The capillary wall • White blood cells • Platelets. • These inflammatory mediators result in vasodilatation and increased vessel permeability. • This leads to fluid loss from the circulation into the interstitial space.

Systemic effects • Systemic effects occur if the burn covers more than 20% of the total body surface area (TBSA). • The systemic effects of a burn include: • Hypovolaemia • Immunosuppression • Catabolism • Loss of the protective function of the gut • Pulmonary oedema.

Inhalational injury Factors suggestive of inhalational injury Inhalational injury is suggested by the following. • The history of the incident • A fire in an enclosed space • The patient lying unconscious in a fire • Symptoms: • A hoarse or weak voice • Increasing stridor • A brassy cough • Restlessness • Respiratory difficulty • Signs: • Soot around the mouth and nose • Singed facial and nasal hair • A swollen upper airway • Hypoxia • Pulmonary oedema • The development of adult respiratory distress syndrome (ARDS).

Types of inhalational injury Supraglottic • This is caused by heat. • If this injury is suspected, it is imperative to secure the airway before further swelling develops. • A tracheostomy should be considered in severe cases.

Subglottic • This is caused by the products of combustion. • Patients with this injury may require respiratory support, which may consist of: • Humidified oxygen • Intubation to allow bronchial toilet • Intermittent positive pressure ventilation (IPPV).

Systemic • This may result from the inhalation of carbon monoxide (CO) or cyanide. • These patients may require respiratory support.

Carbon monoxide poisoning • CO has 250 times the affinity for haemoglobin as oxygen. • The half life of CO in patients breathing room air is 250 min. • The half life of CO in patients breathing 100% oxygen is 40 min. • CO binds to the intracellular cytochrome system, producing sick cell syndrome. • CO levels of 0–15% may be present in smokers or truck drivers. • CO levels of 15–20% result in headache and confusion. • CO levels of 20–40% result in hallucinations and ataxia. • CO levels of 60% are fatal.

Treatment • CO poisoning should be treated with 100% humidified oxygen, delivered at 8 L/min through a non-rebreathing mask with a reservoir. • It important to continue 100% oxygen treatment for 48 h following injury, as a secondary release of CO occurs from the cytochrome system.