Burns/Inhalational Injury


Types of Burn Injuries

  • Scald Burns
    • Account for majority of pediatric burns
    • More likely to be associated with child abuse (glove/stalking, symmetric burns of buttocks/legs/perineum)
  • Thermal Burns
    • Secondary to flame or contact with hot objects
    • Generally minor
    • Mortality influenced by size of burn, patient age, +/- inhalational injury
  • Electrical Burns
    • Rare but serious. Lack of obvious skin damage can mask serious underlying soft tissue injury
    • AC more dangerous than DC (tetanic contractions from cyclic flow of electricity)
    • "Let go" threshold, max current one an grasp and "let go" lower for children than adults
  • Chemical Burns
    • Alkali drain cleaners, hydroflouoric acid, etc
    • DO NOT NEUTRALIZE acid or base as leads to exothermic reaction that can worsen injury
    • Treat with copious irrigation 

Assessment of Burns

Burn Degree

  • First degree
    • Superficial, erythematous without blistering. Painful. Blanch easily, spares dermis. heals in 2-3 days. i.e sunburn
  • Second degree
    • Partial thickness involving all of epidermis and either superficial dermis or deep dermis 
    • Fluid filled blisters at dermis-epidermis junction
    • Burns that extend to superficial dermis are erythematous underneath the blister and heal in 2 weeks
    • Burns that extend to deep dermis can appear mottled with variable color. Do not blanch easily, less painful as a result of nerve injury. Typically requires excision and grafting as can lead to scarring and contractures
  • Third degree burns
    • Full thickness burns requiring definitive surgical management.
    • White, cherry red, brown, black and do not blanch with pressure. Dry/leathery compared to normal skin. Insensate

Zones of Injury

  • Zone of coagulation: necrotic tissue closest to site
  • Zone of hyperemia: uninjured skin with increased blood flow
  • Zone of stasis: located between zones of coagulation and hyperemia and represents area of ongoing inury

Estimating Extent of Burn

  • TBSA correlates with LOS and mortality but has been shown to be overestimated by up to 75% by initial care provider
  • Rule of nines for adults and modified for children due to relatively larger heads and smaller extremities in children (see diagram below)
  • Patient's palm and fingers accounts for ~1% of normal BSA

Treatment

Initial Evaluation

  • Wash with tepid water
  • Chemical burns should be copiously flushed to remove inciting agent
  • Evaluate for other sources of trauma (~10% of all burn patients have additional traumatic injuries)
  • Evaluate for signs of inhalational injury (singed nasal hairs, carbonaceous sputum, facial burns, hypoxia)
  • IV access in any patient with greater than 10% TBSA
  • Assess TBSA. >10% TBSA in infants/children or if suspicion of inhalation injury warrants admission
  • Avoid wet dressings as can precipitate hypothermia

Resuscitation

  • Parkland formula (4 cc/kg/%TBSA over first 24 hours with half in first 8 hours and half in subsequent 16 hours) tends to overestimate fluid needs leading to overresuscitation although no clinical difference in outcome has been found between the two formulas
  • Modified Brooke Formula (2 cc/kg/%TBSA) of crystalloid
  • Titrate fluids for clinical endpoints (urine output of 0.5-1cc/kg/hr) and normal hemoydnamic parameters. Little/no role for bolus fluid therapy
  • No clear difference with colloid vs. crystalloid. Per UM policies, switch to 5% albumin as part of the difficult fluid resuscitation pathway (projected >6 cc/kg/%TBSA in first 24 hours). 
  • Want to balance restoring adequate volume and perfusion vs. over-resuscitation and complications such as compartment syndrome, reperfusion injury, or ARDS
  • Eval for compartment syndrome: Can insert 18 gauge needle connected to arterial pressure transducer and place into subcutaneous/subfascial tissue. Compartment pressure >30 mmHg diagnostic, requires escharatomy or fasciotomy (alternatively, some use a delta of less than 30 mmHg between compartment pressure and diastolic blood pressure as an indication for critically impaired perfusion pressure and need for fasciotomy).
  • Intraabdominal hypertension seen in up to 70% of those with extensive burns. Bladder pressure measurements crucial (12-20 mmHg consistent with IAH and >20mmHg consistent with ACS in adults)

Inhalational Injury

  • Clear link between inhalation injury and mortality- single most important risk factor for mortality1
  • Pathophysiology involves inflammatory response, capillary leak, reactive oxygen species, tissue edema, airway casts/obstruction, direct cellular damage
  • Pulmonary insufficiency at ~36 hours, pulmonary edema at 48-96 hours, and bronchopneumonia at 3-10 days postburn
  • Bronchoscopy gold standard for diagnosis of inhalational injury
  • Incomplete oxidation of hydrocarbons leads to formation of CO. Treat with 100% oxygen as half life of carboxyhemoglobin is 240-320 minutes but decreases to 40-80 minutes with 100% oxygen
  • Cyanide, produced by combustion of carbon and nitrogen containing substances inhibits oxidative phosphorylation (cytochrome c oxidase) and produces relative tissue anoxia and acidosis. Treat with sodium thiosulfate and sodium nitrite
  • Early endotracheal intubation
  • O2 therapy at 100% to treat increased carboyhemoglobin levels until <10% and normalization of acidosis
  • Arterial blood gases needed initially as pulse oximetry may be inaccurate and cooximetry is needed to measure CO-Hb levels
  • Mechanical ventilation, APRV, HFOV all potential options
  • Nebulized heparin or tPa, N-acetylcysteine, bronchodilators, iNO
  • Corticosteroids not currently recommended
  • VV ECMO also an option, even in the setting of external burns

Nutrition

  • Minimize catabolism and the hypermetabolic state: metoprolol
  • Promote anabolism: oxandrelone 10 mg PO BID
  • Prealbumin <15 mg/dl consistent with malnutrition
  • Enteral feeding ideal route, initiate upon stabilization. TPN if unable to tolerate

Wound Care

  • Wounds colonized within first few hours with GPC's such as staph aureus and staph epidermidis and subsequently colonized with gut flora such as pseudomonas, enterobacter, and E. Coli by 5 days. Topical agents such as silvadene used to control colonization although it delays wound healing. Mepilex, Acticoat, Mepitel sometimes used
  • Early debridement crucial. Excision and skin grafting per burn surgeons

References

1) S.E. Wolf, J.K. Rose, M.H. Desai, et al.: Mortality determinants in massive pediatric burns. An analysis of 103 children with > or = 80% TBSA burns (> or = 70% full-thickness). Ann Surg. 225:554-565 1997
2) Pediatric Burn Injury Presentation: Drs. S Tomlinson, D Nguyen, and L Metzler 2016.