Aetiology

• Thermal
  
• Chemical
  
• Electrical
  
• Cold injury
  
• Radiation.

Depth

• Superficial (epidermal only)
  
• Superficial dermal
  
• Deep dermal
  
• Full thickness.

Body surface area involved

• Burns >15% TBSA in adults or >10% in children require formal resuscitation.

Local effects

Jackson’s burn wound model describes three zones of injury:

1. Inner zone of coagulation (coagulative necrosis)
   
   
   
   • Cell death and coagulation of cellular proteins.
   
   
2. Intermediate zone of stasis
   
   
   
   • Damage to microcirculation causing ischaemia which, untreated, proceeds to necrosis.
     
   • The extent of progression is influenced by effective resuscitation.
   
   
3. Outer zone of hyperaemia
   
   
   
   • Cellular damage triggers release of inflammatory mediators.
     
   • Inflammatory mediators are released from:
     
     
     
     • Capillary wall
       
     • White blood cells
       
     • Platelets.
     
     
   • Examples: histamine, catecholamines, free oxygen radicals, platelet activating factor, arachidonic acid breakdown products.
     
   • These result in vasodilatation and increased vessel permeability.
     
   • Leads to fluid loss from the circulation into the interstitial space.

Systemic effects

• Systemic effects occur if >25–30% TBSA is burned.
  
  
  
  • Conceptually, this is the zone of hyperaemia, which is so extensive that it involves the whole body.
    
  • Mediated by overspill of local inflammatory mediators into the systemic circulation.
    
    
    
    • Examples: TNF, interleukins and interferon.
  
  
• Early excision and closure of the burn wound limits systemic inflammation.
  
• The systemic effects of a burn impact on all organ systems:
  
  
  
  • Hypovolaemia
    
  • Myocardial depression
    
  • Pulmonary oedema
    
  • Renal impairment
    
  • Hepatic dysfunction
    
  • Catabolism with increased metabolic rate
    
  • Immunosuppression
    
  • Loss of the protective function of the gut
    
  • Psychological effects.

Initial management

• Burn is trauma; should be approached in an ATLS-style.
  
• Airway may have sustained inhalation injury.
  
  
  
  • Intubation required if airway patency is at risk or oedema expected.
    
  • The tube is left uncut in case of subsequent facial swelling.
  
  
• Profound hypovolaemia is not caused by acute burns—other causes of shock should be sought.
  
• The cutaneous burn is considered after the secondary survey is underway and immediate life-threatening injuries have been dealt with.
  
• Exposure allows the TBSA of burn to be estimated and guide initial fluid resuscitation.
  
• Two large-bore IV cannulas inserted (through burnt skin if necessary); blood sent for baseline investigations.
  
• Analgesia and fluid resuscitation.
  
• Urinary catheter to assess adequacy of fluid resuscitation.
  
• Nasogastric tube to decompress the stomach.
  
  
  
  • Also used to start early feeding to provide nutrition and gut protection.
  
  
• The wound is dressed, often with cling film in the first instance:
  
  
  
  • Decreases evaporative fluid loss
    
  • Allows reassessment without removal of dressing
    
  • Helps pain relief.

History

• An ‘AMPLE’ history is taken if possible.
  
  
  
  • Helps predict likelihood of inhalation injury, depth of burn, probability of other injuries.
  
  
• Aim to establish the following facts:
  
  
  
  • Mechanism of injury (what happened, where, when, how and why)
    
  • Loss of consciousness
    
  • What first aid was given and for how long
    
  • What treatment received so far
    
  • Tetanus status.
  
  
• Regarding scalds:
  
  
  
  • How recently had the kettle boiled?
    
  • Was cold milk added to the tea/coffee?
    
  • What was in the saucepan?
    
    
    
    • Soups, oil, vegetables or rice boil at higher temperatures than water.
  
  
• Regarding electrical injuries:
  
  
  
  • Voltage—domestic or industrial
    
  • Associated flash
    
  • Associated clothing fire.
  
  
• Regarding chemical injuries:
  
  
  
  • What chemical
    
  • Length of time exposed to the chemical
    
  • Specific antidotes used.

Estimating burn depth

• Burns are assessed clinically by their appearance.
  
• Blisters are de-roofed to assess the base of the wound.

Depth	Appearance	Blanching	Sensation	Blisters	Healing
Superficial	Red, like sunburn		Painful
Superficial dermal	Pink and moist		Painful
Deep dermal	Mottled white and ‘cherry red’ fixed staining		Dull
Full thickness	Leathery white/yellow		None

• Some use Laser Doppler Imaging to estimate blood flow within the wound, which correlates with burn depth.

Estimating the surface area of a burn

• Erythema should not be included.
  
  
  
  • Erythema fades within hours—accurate burn estimation is a dynamic process.

Diagnosis

• Inhalation injury is a clinical diagnosis.
  
• Chest X-ray and arterial blood gas analysis may initially be normal.
  
• Carboxyhaemoglobin levels are useful, but may be normal if patients receive oxygen during transfer to hospital.
  
• Fibre-optic bronchoscopy is most reliable for making the diagnosis.
  
• Characteristic bronchoscopic findings:
  
  
  
  • Soot below the vocal cords
    
  • Hyperaemia
    
  • Mucosal oedema and ulceration.

Factors suggestive of inhalation injury

• History of inhaled hot gases and vapours given off by a fire:
  
  
  
  • Fire in an enclosed space
    
  • Patients found unconscious in a fire.
  
  
• Symptoms
  
  
  
  • Hoarse or weak voice
    
  • Brassy cough
    
  • Restlessness
    
  • Shortness of breath
  
  
• Signs
  
  
  
  • Soot around the mouth and nose
    
  • Singed facial and nasal hair
    
  • Deep burns to face, neck and upper body
    
  • Carbonaceous sputum or carbon deposits in the mouth and oropharynx
    
  • Swollen upper airway
    
  • Stridor
    
  • Dyspnoea
    
  • Hypoxia
    
  • Pulmonary oedema.

Classification of inhalation injury

Carbon monoxide poisoning

• CO has 250 times the affinity for deoxyhaemoglobin as oxygen.
  
  
  
  • Half life of CO in patients breathing room air is ≈250 minutes.
    
  • Half life of CO in patients breathing 100% oxygen is ≈40 minutes.
  
  
• CO binds to intracellular cytochrome proteins, affecting mitochondria.
  
  
  
  • Levels up to 10% may be found in smokers or truck drivers.
    
  • 15–20% cause headache and confusion.
    
  • 20–40% cause hallucinations and ataxia.
    
  • CO levels of 60% are fatal.
  
  
• Arterial blood gas analysis shows elevated carboxyhaemoglobin and metabolic acidosis.
  
• Pulse oximetry cannot differentiate between oxy- and carboxyhaemoglobin.

Tracheostomy

• There is no consensus on tracheostomy use in burn patients.
  
• Often used in patients with large burns and inhalation injury.
  
  
  
  • They typically require repeated surgeries and prolonged ventilation.
  
  
• Benefits of tracheostomy in inhalation injury:
  
  
  
  • Ease of access to the bronchopulmonary tree for toileting and lavage.
    
  • Improved ventilator weaning by reducing:
    
    
    
    • Dead space (10–50% less than endotracheal tube)
      
    • Airway resistance
      
    • Work of breathing
      
    • Sedation requirements.
  
  
• Complications of tracheostomy:
  
  
  
  • Bleeding from the wound or erosion of brachiocephalic vessels
    
  • Accidental decannulation
    
  • Swallowing dysfunction
    
  • Tracheal ulceration and granulation tissue
    
  • Tracheo-oesophageal fistula
    
  • Tracheal stenosis.

Complications of inhalation injury

1. Complications of mechanical ventilation
   
   
   
   • Barotrauma and pneumothorax result from high ventilatory pressures required to overcome poor lung compliance and increased airways resistance seen in ARDS.
     
   • This can be avoided by employing lung protective ventilation strategies:
     
     
     
     • Pressure controlled ventilation
       
     • High ventilation rate
       
     • Small tidal volumes
       
     • Inverse ratio ventilation
       
     • Physiological PEEP (approximately 5 cm H₂O)
       
     • Lower target oxygen saturation of 92%
       
     • Permissive hypercapnia and respiratory acidosis.
     
     
   • High-frequency oscillatory ventilation can be used as a rescue strategy when conventional ventilation fails.
   
   
2. Complications of long-term intubation or tracheostomy
   
   
   
   • Tracheomalacia
     
   • Tracheal stenosis.
   
   
3. Complications of persistent inflammation
   
   
   
   • ARDS
     
   • Multiple organ dysfunction syndrome (MODS)
     
   • In the long-term, fibrosis can lead to emphysema and bronchiectasis.

Parkland

• 4 ml/kg/% burn of Hartmann’s solution in the first 24 hours after the burn.
  
  
  
  • Half the fluid is given in the first 8 hours after injury.
    
  • The second half is given in the next 16 hours.
  
  
• Hartmann’s solution contains:
  
  
  
  • Na⁺ 131 mmol/l
    

    Cl⁻ 111 mmol/l

    
    

    Lactate 29 mmol/l

    
    

    K⁺ 5 mmol/l

    
    

    Ca²⁺ 2 mmol/l.

Muir and Barclay

• Calculates the volume of human albumin solution to be given in the first 36 hours following a burn:
  
  
  
  • 0.5 ml/kg/% burn gives a volume to be infused in each time period.
    
  • The time periods are 3 × 4 hours, 2 × 6 hours and 1 × 12 hours.
  
  
• Formulas give only estimates of fluid requirements.
  
• They are unreliable at the extremes of age.
  
• More fluid may be required for:
  
  
  
  • Paediatric burns
    
  • Delayed resuscitation
    
  • Large burns
    
  • Deep burns
    
  • Burns where an accelerant, such as petrol, was used
    
  • Electrical burns
    
  • Inhalation injury
    
  • Coexisting polytrauma.
  
  
• Charles Baxter, who described the Parkland formula, reviewed its use:
  
  
  
  • Accurate in 70% of adults.
    
  • Overestimated in 18%; underestimated in 12%.
    
  • Most often inadequate for burns >80% TBSA and patients >45 years.
    
  • Few paediatric cases fell outside a range of 3.7–4.3 ml/kg/% TBSA burn.
  
  
• The rate of infusion is modified to meet specific end points of resuscitation:
  
  
  
  • Urine output is the best indicator of tissue perfusion
    
    
    
    • Aim for 0.5–1 ml/kg/h in adults; 1–1.5 ml/kg/h in children
      
    • Double this after high-voltage electrical injuries.
    
    
  • Other parameters to be monitored:
    
    
    
    • Pulse, blood pressure, capillary refill
      
    • Core–peripheral temperature gradient
      
    • Respiratory rate
      
    • Urine osmolality.
  
  
• Serial measures of arterial blood lactate and base excess also indicate adequacy of resuscitation.
  
• Direct measurement of cardiac output with transoesophageal Doppler can identify patients who would benefit from inotropes or vasopressors.
  
  
  
  • Inotrope of choice: norepinephrine; preferred vasopressor: dobutamine.
    
  • Drugs are not used to ‘treat’ low urine output without first ruling out hypovolaemia, which is treated with more fluid.
    
  • Injudicious vasopressor use worsens tissue hypoperfusion, causing extension of the burn and poor skin graft take.

Factors specific to children

• Proportionately greater surface area than adults.
  
• Reduced physiological reserves.
  
  
  
  • Because of this, children require additional maintenance fluid containing dextrose.
  
  
• Daily maintenance fluid requirement:
  
  
  
  • 100 ml/kg for the first 10 kg body weight
    
  • 50 ml/kg for the next 10 kg body weight
    
  • 20 ml/kg for the remainder of the body weight
  
  
• Maintenance fluid is given enterally whenever possible.

Complications of fluid resuscitation

• Under-resuscitation
  
  
  
  • Hypovolaemia
    
  • Shock
    
  • Renal failure
    
  • Ischaemia-reperfusion injury
    
  • MODS.
  
  
• Over-resuscitation
  
  
  
  • Generalised oedema
    
  • Pulmonary oedema
    
  • Cerebral oedema
    
  • Intestinal oedema
    
  • Compartment syndrome of limbs and abdomen.
  
  
• Both under- and over-resuscitation may deepen the burn wound.