Burns

Epidemiology and Risk Factors

Burns are:

  • Common
    ~1% of persons.
    • ~10% require hospitalisation

Pathophysiology

Thermal injury results in:

  • Local response
    • Tissue damage
      Jacksons Model:
      • Zone of coagulation
      • Zone of stasis
        Compromised but viable cells.
        • Amenable to treatment
        • Have impaired blood flow
      • Zone of stasis loss
    • Inflammation
      • Fluid extravasation
        • Greatest in first eight hours
        • Continues up to 24 hours
  • Systemic effects
    Significant when >20% BSA.
    • ↓ CO in first 24-48 hours
      • Hypovolaemia
      • ↑ Blood viscosity
      • Inflammatory soup acts as negative inotrope
    • ↑ CO after 72 hours
      Hypermetabolic response.

Eschar:

  • Burnt dermis forming a non-elastic eschar atop of skin
  • Circumferential eschar formation leads to compartment syndrome compressing oedematous tissue

Electrical burns:

  • High resistance tissues produce excessive heat
    • Bone generates substantial heat
      Leads to muscular burns, leading to:
      • Rhabdomyolysis
        • Fasciotomy (in addition to escharotomy)
    • May have significant underlying tissue damage that is disproportionate to overlying features
Electrical Burn

Aetiology

Assessment

Burns are dynamic and will evolve and either improve or deteriorate depend on therapy

Assess:

  • Depth
    • Superficial
      Epidermal burn.
      • Red and painful
      • Healing within 1 week
      • Not included in BSA calculation
    • Superficial dermal
      Dermal burn.
      • Blistering
      • Capillary return present
      • Healing is slower
    • Deep dermal
      • Dark red
        Cooked haemoglobin locked in tissue.
      • May not blister
      • No capillary refill
    • Full thickness
      • White/waxy/charred
      • Insensate
        No pain.
      • No blisters
      • No capillary refill
        No viable blood vessels.
      • Act as a focus for infection.
  • Size
    Remember to exclude superficial burns.
    • Rule of 9’s
      • Patient palm is 1%
    • Lund and Browder chart

History

Examination

Investigations

Diagnostic Approach and DDx

Management

  • First aid and primary survey
  • Transfer to burns centre
  • Fluid resuscitation to moderate hypovolaemia
  • Appropriate debridement and burn care

Burn patients are trauma patients and should be evaluated as such. Details of the primary survey are covered at Primary Survey.

Resuscitation:

  • First aid
    • Remove from heat source
    • Cool the burn
      Under tepid water for 20 minutes.
  • A
  • C
    • Fluid resuscitation
      Required for burns >10% in children and elderly, and >15% in adults.
      • Modified Parkland formula
        Most commonly used protocol for burns resuscitation.
        • For burns >20% BSA (or 10% in children)
        • 3mL/kg/% BSA burn to calculate first 24/24 fluid requirement
          • Use lactated ringers or CSL
          • Give half over the first 8 hours
          • Titrate to urine output
            • Aim 0.5-1mL/kg/hr in adults
            • Aim 1-2mL/kg/hr in children
      • Avoid over-resuscitation and fluid creep
        Excessive volume leads to multiorgan complications
        • Airway occlusion
        • Pulmonary oedema
        • Abdominal compartment syndrome
      • Consider albumin
      • Fluid therapy is ↓ as enteral intake is ↑

Specific therapy:

  • Pharmacological
    • Analgesia
      Multimodal:
      • Opioid
      • Ketamine
  • Procedural
    • Escharotomy
      • Important in:
        • Limbs
          Compartment syndrome.
        • Chest
          Respiratory failure.
        • Abdomen
          Abdominal compartment syndrome.
      • Cut down to viable tissue
        Can be performed under LA as eschar is insensate.
      • Precise location for cut is not essential
      • Tissue will ‘spring’ out as pressure released
    • Surgical care
      • Wound excision and debridement
        ↓ Bacterial colonisation.
      • Dressings
      • Grafting
        • May be limited by availability of unburned skin Skin can be re-harvested every ~2 weeks.
        • ‘Meshing’ skin graft allows graft to be applied to skin in a 4:1 ratio
          Taking skin in a ‘chicken-wire’ fashion.
        • Cadaveric skin can be used for temporary coverage, although autologous grafting is best
        • Artificial substances:
          • Biobrane
            Silicone and porcine collagen.
            • Temporary dressing for intermediate and deep dermal burns
            • Early application beneficial
              Reduces tissue damage and systemic inflammatory response.
          • Biodegradable Tissue Matrix
  • Physical

Supportive care:

Burn recovery is a hypermetabolic state; energy expenditure may be doubled and significant amounts of trace elements are lost in wound exudate.

  • G
    • Nutrition
      • Feed within 12 hours
        May need 25-30kcal/kg/day due to ↑ metabolism.
      • Trace element supplementation
  • H
    • Thromboprophylaxis
      Critical due to the high risk of VTE. Described regimens include:
      • Heparin 5000 units Q8H
      • Enoxaparin 0.5mg/kg Q12H
      • Enoxaparin Q12H, adjusted to target anti-Xa 0.2-0.4 IU/mL
  • I
    • Infection monitoring

Disposition:

  • Transfer to burns centre if:
    • ⩾10% BSA full thickness, ⩾5% in children
    • Burns to key areas
      • Face
      • Hands
      • Feet
      • Perineum
    • Electrical and chemical
    • Inhalational injury
    • Circumferential

Preventative:

Marginal and Ineffective Therapies

Anaesthetic Considerations

  • A
    • Airway security
      May be impossible to get access again.
    • Facial burns
      • Painful mask application
      • NGT/tubes
  • B
    • Inhalational injury
  • C
    • Arterial line
      No NIBP on burnt skin.
    • Fluid management
    • IV access
      • Ideally through unburnt skin
  • D
    • Analgesia
      Substantial pain.
      • Multimodal
      • Early anti-neuropathics
      • Single-shot regional ideal
  • E
    • Suxamethonium contraindicated
      From 48 hours to 2 years.
    • Temperature management
      • Warm theatre
        28°C.
      • Warming lines
      • Warming CVCs
        Slow rate of cooling but often unsuccessful warming.
      • Abandon procedure if unmanageable hypothermia (⩽35°C)
    • Positioning difficult
  • G
    • Hypermetabolic
      Rapid consumption of neuromuscular blockers.
  • H
    • Bleeding can be substantial
      • Prepare for massive transfusion
        Hard to overtransfuse.
        • Hb >100g/L prior to procedure ideal
        • ABG every half hour to measure Hb
      • Tumescent preparation
        1:500,000 adrenaline infiltrated widely subcutaneously under sites prior to debridement results in substantial reduction in blood loss without adverse effect on graft success.
      • Bleeding will continue post-operatively
    • Coagulopathy
  • I
    • Sepsis

Complications

  • D
    • Cosmetic
    • Chronic pain
  • E
    • Contractures
    • Rhabdomyolysis
  • F
    • AKI
      • Pre-renal
      • Haemoglobinuria
      • Myoglobinuria
    • Hypernatraemia
  • I
    • Sepsis
      Often occurs due to the combination of:
      • Deep injuries
      • Disrupted wound healing
      • Immune dysfunction

Prognosis

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.