Burns

Thermal, chemical, electrical or radiation injury to the skin and deeper tissues, producing coagulative necrosis with a surrounding zone of stasis and an outer zone of hyperaemia. The zone of stasis is potentially salvageable and its fate determines the final depth of the burn, which is why adequate resuscitation, warming and avoidance of hypotension convert a partial thickness injury into a healing wound rather than a full thickness one.

Pathophysiology of burn shock

Burns above roughly 20 percent total body surface area produce a systemic inflammatory response with massive release of histamine, prostaglandins, bradykinin, thromboxane and cytokines. The consequences are:

• Generalised capillary leak with loss of plasma into the interstitium, not only at the burn site but throughout the body, producing hypovolaemic shock with a normal or raised haematocrit.
• Reduced myocardial contractility from circulating myocardial depressant factors in the first 24 to 48 hours, so the shock is distributive and cardiogenic as well as hypovolaemic.
• Increased evaporative water loss through the lost epidermal barrier, which continues for days.
• A hypermetabolic state after 48 hours with a resting energy expenditure that may double, driving muscle catabolism, immunosuppression and impaired healing.

Fluid losses are maximal in the first 8 hours and decline over 24 to 36 hours, which is the basis for giving half the calculated first day volume in the first 8 hours from the time of injury rather than from the time of arrival.

Depth classification and its clinical meaning

• Superficial, that is first degree: epidermis only, from ultraviolet exposure or brief flash. Red, dry, hypersensitive, blanches, no blisters. Heals in under 7 days without scarring. Excluded entirely from the total body surface area calculation, which is the single most common error in burn fluid prescribing.
• Superficial partial thickness, that is superficial second degree: epidermis and upper dermis, usually from scald. Red, moist, weeping, with blisters that blanch briskly on pressure and refill rapidly. Intensely painful because nerve endings are exposed. Heals in 7 to 14 days without scarring, though pigmentary change is common.
• Deep partial thickness, that is deep second degree: epidermis and deep dermis, from scald, flame, chemicals, oil and grease. Cheesy white, waxy, wet or dry, does not blanch, sensation is reduced. Healing takes more than 21 days with severe scarring and contracture, so these are usually excised and grafted rather than allowed to heal.
• Full thickness, that is third degree: entire epidermis and dermis destroyed with no residual epithelial elements. Grey to charred and black, dry, leathery, contracted, insensate. Requires excision and grafting.
• Fourth degree: extension into muscle.
• Fifth degree: extension into bone, seen particularly in patients with epilepsy who convulse into a fire and cannot withdraw.

Burn depth evolves over 48 to 72 hours, so early assessment underestimates final depth and reassessment is mandatory.

Estimating total body surface area

• Wallace rule of nines in adults: head and neck 9 percent, each arm 9 percent, anterior trunk 18 percent, posterior trunk 18 percent, each leg 18 percent, genitalia and perineum 1 percent.
• The rule of nines is inaccurate in children, in whom the head is proportionally much larger and the legs smaller. Use a Lund and Browder chart, which adjusts by age: the head is around 19 percent at birth, falling by roughly 1 percent per year of life to adult proportions, with the difference added to the lower limbs.
• The patient's palm including the fingers is approximately 1 percent of their own body surface area, and is useful for small scattered burns under 15 percent or for estimating unburnt skin in very extensive burns above 85 percent. It is unreliable for medium sized burns, where a chart must be used.
• Overestimation is common and leads to over resuscitation, which causes abdominal and extremity compartment syndrome, pulmonary oedema and conversion of the zone of stasis. Recalculate carefully rather than accepting a rough field estimate.

History that changes management

• Mechanism: flame, scald, contact, chemical, electrical, friction or radiation.
• Enclosed space exposure, duration of exposure and loss of consciousness, which predict inhalational injury and carbon monoxide poisoning.
• Time of injury, which starts the resuscitation clock.
• Voltage in electrical injury, and whether the current was alternating, which causes tetanic muscle contraction and prevents release.
• Chemical agent, concentration and duration of contact.
• Comorbidity, medication, allergies, tetanus status, pregnancy and last oral intake.
• In children, the mechanism must be consistent with the injury pattern and the developmental stage. Sharply demarcated stocking or glove distribution scalds, symmetrical burns, buttock and perineal immersion burns, contact burns of uniform depth in the shape of an object, and any delay in presentation raise the possibility of non accidental injury and mandate safeguarding involvement.

Features of inhalational injury, which must be sought actively

• Facial and neck burns, singed nasal vibrissae and eyebrows.
• Carbonaceous sputum and soot in the oropharynx.
• Hoarseness, stridor and air hunger.
• Cough, wheeze and dyspnoea.
• Burns sustained in an enclosed space.
• Reduced consciousness at the scene.
• Perioral and intraoral burns.

The airway in a burns patient deteriorates over hours as oedema develops, and a patient who looks manageable on arrival may become unintubatable by the time obstruction is obvious. Intubate early rather than late.

Features of shock

Tachycardia, delayed capillary refill, cool peripheries, reduced urine output, agitation and confusion. Hypotension is a late sign in a young patient and its presence indicates advanced shock or an additional cause such as haemorrhage from concomitant trauma. Burns alone rarely cause hypotension in the first hour, so hypotension early after injury should prompt a search for another injury.

Circumferential burns

Full thickness eschar is inelastic. Circumferential limb burns produce a tourniquet effect with progressive vascular compromise, and circumferential chest and abdominal burns restrict ventilation with rising airway pressures and falling tidal volumes. Both worsen as oedema accumulates over the first 24 hours.

Primary survey with cervical spine consideration

• Catastrophic haemorrhage and cervical spine: if trauma is suspected, use manual in line stabilisation and secure the head with blocks or blanket rolls taped to the head and trolley. A rigid collar over burnt neck skin obscures assessment, worsens oedema and impedes the airway, so it is avoided in the burnt neck.
• Airway: assess patency and maintainability. Indications for intubation are pharyngeal or laryngeal burns, stridor, hoarseness, air hunger, carbonaceous sputum, reduced consciousness, hypoxia with severe smoke inhalation, and flame or flash burns involving the face and neck. Use an uncut endotracheal tube, since facial oedema will displace a cut tube, and secure it with tape around the head rather than adhesive on burnt skin.
• Breathing: respiratory rate, oxygen saturation and bilateral air entry. Give high flow oxygen at 15 litres per minute through a non rebreathing mask to every significant burn regardless of saturation, to displace carbon monoxide.
• Circulation: control active bleeding, assess pulse, blood pressure and perfusion. Obtain two large bore cannulae, through unburnt skin where possible, but through burnt skin if necessary rather than delaying. Intraosseous access is acceptable. Perform an electrocardiogram after any electrical burn.
• Disability: Glasgow Coma Scale, pupils and capillary blood glucose, which is checked in every patient.
• Exposure: remove all clothing and jewellery before oedema makes rings and bracelets tourniquets, examine the whole body including the back, then cover the patient. Hypothermia is a major and preventable cause of mortality in burns, since the patient has lost the thermoregulatory barrier and is being irrigated with fluid. Warm the room, use warmed fluids and cover with clean dry sheets and blankets.

Investigations

• Capillary blood glucose in all.
• Full blood count, urea and electrolytes, creatinine, group and save or crossmatch.
• Arterial or venous blood gas with lactate.
• Carboxyhaemoglobin level. Pulse oximetry is falsely normal in carbon monoxide poisoning because carboxyhaemoglobin and oxyhaemoglobin absorb light similarly, so a normal saturation in a fire victim provides no reassurance.
• Serum lactate, which is a marker of cyanide toxicity when markedly elevated and disproportionate to the clinical picture in a patient from a house fire with burning plastics and synthetic materials.
• Creatine kinase and urinalysis for myoglobinuria in electrical and deep burns.
• Chest radiography, which is often normal early in inhalational injury and does not exclude it.
• Twelve lead electrocardiogram for all electrical burns, with cardiac monitoring for high voltage injury, loss of consciousness, arrhythmia or an abnormal initial tracing.
• Fibreoptic bronchoscopy to confirm and grade inhalational injury where available.
• Pregnancy test in women of childbearing age.
• Trauma imaging where the mechanism includes blast, fall or road traffic injury.

Criteria for referral to a burns centre

• Partial thickness burns above 10 percent total body surface area in adults, and above 5 percent in children and the elderly.
• Any full thickness burn.
• Burns of the face, hands, feet, genitalia, perineum or major joints.
• Circumferential burns of the limbs or chest.
• Electrical burns including lightning, and chemical burns.
• Inhalational injury.
• Burns in patients with significant pre existing disease that will complicate management or affect mortality.
• Burns with concomitant trauma, where the greater immediate risk determines where the patient goes first.
• Paediatric burns where non accidental injury is suspected.
• Burns in patients requiring social, emotional or rehabilitative support beyond local capability.
• Septic burn wounds.

First aid, which materially changes outcome

• Stop the burning process: remove from the source, extinguish flames, remove smouldering and chemically soaked clothing.
• Cool the burn with running cool water at approximately 15 degrees Celsius for 20 minutes, effective for up to 3 hours after injury. This reduces depth, reduces pain and reduces the need for grafting. Do not use ice or iced water, which causes vasoconstriction and deepens the injury.
• Cool the burn but warm the patient. Cooling a large burn in a child causes dangerous hypothermia, so cool in stages and monitor temperature.
• Chemical burns: brush off dry powder first, then irrigate copiously for at least 20 to 30 minutes, and longer for alkalis which penetrate progressively through liquefactive necrosis. Do not attempt chemical neutralisation, which generates heat. Hydrofluoric acid requires topical calcium gluconate gel, and for deep or extensive exposure intra arterial or intravenous calcium gluconate with monitoring for hypocalcaemia and arrhythmia.
• Electrical burns: ensure the source is isolated before approach. The visible skin injury underestimates deep tissue destruction enormously.
• Cover the burn with cling film applied in longitudinal strips rather than circumferentially, or with a clean dry sheet.

Fluid resuscitation

Indicated for burns above 15 percent total body surface area in adults and above 10 percent in children, and earlier where there is shock or inhalational injury.

• Parkland formula: 4 mL per kg per percentage total body surface area of Ringer lactate in the first 24 hours from the time of injury, with half given in the first 8 hours and the remaining half over the subsequent 16 hours. If the patient presents late, the first half must still be delivered by 8 hours from injury, which means a faster initial rate.
• Modified formulas using 2 to 3 mL per kg per percent are increasingly used to reduce over resuscitation, with titration to urine output as the true determinant.
• Ringer lactate is the preferred crystalloid, since large volumes of 0.9 percent sodium chloride produce hyperchloraemic acidosis.
• Children additionally require maintenance fluid containing glucose, since they have limited glycogen reserves. Use 4 mL/kg/hour for the first 10 kg, 2 mL/kg/hour for the next 10 kg and 1 mL/kg/hour thereafter, with a dextrose containing solution, in addition to the resuscitation volume.
• The formula is a starting point, not a prescription. Titrate to urine output: 0.5 mL/kg/hour in adults and 1 mL/kg/hour in children. Insert a urinary catheter in any burn requiring formal resuscitation.
• Aim for 1 to 2 mL/kg/hour of urine output where there is myoglobinuria from electrical or deep burns, with consideration of alkalinisation and mannitol, to prevent pigment nephropathy.
• Recognise over resuscitation, which is now as common a problem as under resuscitation. Rising abdominal pressure, worsening oxygenation, increasing peripheral oedema and rising airway pressures indicate fluid creep, and the rate should be reduced. Consider colloid rescue with albumin after 12 to 24 hours in patients requiring far in excess of predicted volumes.
• Monitor hourly urine output, heart rate, blood pressure, mental status, lactate and base deficit.

Analgesia

Burns pain is severe and is routinely undertreated.

• Intravenous morphine 0.05 to 0.1 mg/kg titrated in increments every 5 minutes to effect, with regular reassessment. In children, 0.1 mg/kg intravenously titrated, or intranasal fentanyl 1.5 micrograms/kg where access is delayed.
• Do not give intramuscular or subcutaneous analgesia in a shocked patient, since absorption is unpredictable and a bolus is delivered when perfusion is restored.
• Regular paracetamol 1 g every 6 hours intravenously or orally, maximum 4 g in 24 hours, as a background agent.
• Add a nonsteroidal anti inflammatory drug where renal function permits and there is no bleeding risk.
• Ketamine 0.25 to 0.5 mg/kg intravenously for dressing changes and procedures, which preserves airway reflexes and haemodynamic stability and is particularly useful in resource limited settings.
• Anxiolysis and non pharmacological measures, since anticipatory anxiety amplifies procedural pain.

Escharotomy

• Indicated for circumferential full thickness limb burns with vascular compromise, indicated by loss of Doppler signal, reduced capillary refill, worsening pain, paraesthesia and increasing compartment pressure; and for circumferential chest or abdominal burns causing restricted ventilation with rising airway pressures.
• Performed at the bedside through insensate eschar, using a scalpel or diathermy, incising through the full thickness of the burn until the underlying fat pouts and the wound edges separate.
• Limb incisions run along the medial and lateral mid axial lines, avoiding the ulnar nerve at the elbow, the common peroneal nerve at the fibular neck, and crossing joints obliquely.
• Chest incisions run down the anterior axillary lines bilaterally, joined by a transverse incision along the costal margin, producing a rectangular release.
• Bleeding can be brisk and requires diathermy haemostasis.
• Fasciotomy, which is a different procedure, is required for electrical injury and deep muscle compartment involvement and must be performed in theatre.

Airway and inhalational injury

• Early intubation for the indications, with an uncut tube.
• Humidified oxygen, nebulised saline and aggressive chest physiotherapy to clear sloughed mucosa and casts.
• Nebulised heparin and N acetylcysteine are used in some protocols for inhalational injury with cast formation, with modest evidence.
• Bronchodilators for bronchospasm.
• Carbon monoxide poisoning: 100 percent oxygen reduces the half life of carboxyhaemoglobin from around 4 hours to under 1 hour. Hyperbaric oxygen is considered for carboxyhaemoglobin above 25 percent, neurological signs, loss of consciousness, pregnancy and cardiac ischaemia, though transfer risk must be weighed against benefit.
• Cyanide toxicity: suspect in a patient from an enclosed fire with soot, reduced consciousness, persistent metabolic acidosis and a lactate above 8 to 10 mmol/L despite resuscitation. Treat with hydroxocobalamin 70 mg/kg intravenously, to a usual adult dose of 5 g, which is safe in the hypotensive patient. Avoid nitrite based kits in a patient who may also have carbon monoxide poisoning, since inducing methaemoglobinaemia further reduces oxygen carriage.

Wound care

• Leave blisters intact where small; deroof large, tense or awkwardly sited blisters, since the blister fluid contains inflammatory mediators and impedes assessment.
• Clean with saline or chlorhexidine solution and cover.
• Silver sulfadiazine 1 percent cream is widely used and has broad antimicrobial cover including Pseudomonas, but it forms a pseudoeschar that obscures wound assessment and delays epithelialisation, so it should not be applied to a burn that will be assessed by a burns unit within hours. Avoid in sulphonamide allergy, in pregnancy at term, and in neonates given kernicterus risk.
• Paraffin gauze, silver impregnated dressings and hydrocolloids for superficial partial thickness wounds.
• Facial burns are managed open with a bland ointment.
• Elevate burnt limbs to reduce oedema.
• Splint hands in the position of safe immobilisation with the metacarpophalangeal joints flexed and the interphalangeal joints extended, to prevent contracture.

Antibiotics, tetanus and other measures

• Do not give prophylactic systemic antibiotics. They do not reduce burn wound infection and they select resistant organisms, which is a major problem in burns units. Antibiotics are given only for documented infection, guided by culture.
• Tetanus prophylaxis: 0.5 mL tetanus toxoid intramuscularly unless three or more doses have been received with the last within 5 years. Add tetanus immunoglobulin for high risk wounds in the incompletely immunised.
• Venous thromboembolism prophylaxis with low molecular weight heparin once bleeding risk is acceptable, since major burns are strongly prothrombotic.
• Stress ulcer prophylaxis with a proton pump inhibitor in major burns, given the risk of Curling ulcer.
• Nasogastric tube for burns above 20 percent, since gastric stasis and ileus are usual, and to permit early enteral feeding.
• Early enteral nutrition within 6 to 12 hours, which preserves gut mucosal integrity, reduces bacterial translocation and blunts the hypermetabolic response. Energy requirements are substantially increased and dietetic involvement is essential.
• Glycaemic control, since hyperglycaemia worsens outcome.
• Keep the patient warm at every stage, including during transfer.

Definitive surgical management

• Early tangential excision and split thickness skin grafting of deep partial and full thickness burns, ideally within the first 3 to 5 days, which reduces infection, blood loss, length of stay and mortality compared with delayed excision.
• Temporary coverage with allograft, xenograft or synthetic dressings where autograft is insufficient in massive burns.
• Meshed grafts to expand coverage in large burns, at the cost of a poorer cosmetic result.
• Sheet grafts to the face, hands and over joints for the best functional and cosmetic outcome.
• Scar management with pressure garments, silicone, massage and splinting from the time of healing, continued for 12 to 18 months while the scar remains active.
• Contracture release and reconstruction later, after scar maturation, except where a contracture threatens function or vision, when earlier release is required.

Rehabilitation and long term care

Physiotherapy and occupational therapy from day one, with ranging of joints and splinting to prevent contracture. Psychological support, since post traumatic stress, depression and body image disturbance are frequent and persistent. Nutritional support through the prolonged hypermetabolic phase. Long term follow up for hypertrophic scarring, contracture, itch, which is often the most distressing late symptom, and for the psychosocial and occupational consequences.