Inhalation Injury

OVERVIEW

  • 20% in burn patients
  • 60% in burns patients with central facial burns
  • causes a massive increase in mortality

PATHOPHYSIOLOGY

Components of smoke that cause damage:

  • heat
  • particulates
  • systemic toxins (CO and CN)
  • respiratory irritants (ammonia, HCl, oxides of nitrogen, phosgene and aldehydes)

Thermal Injury

  • oropharyngeal area
  • lower airway affected if steam, volatile gases, explosive gasses or hot liquids are inhaled

Asphyxiation

  • combustion utilises O2 -> low FiO2 -> hypoxaemia
  • CO: tissue hypoxia, left shifted ODC, cytochrome oxidase binding, myocardial myoglobin binding with decreased contractility
  • CN: poisoning of electron transport chain -> lactic acidosis
  • MetHb: heat denaturation of Hb, oxides produced in fire, nitrites -> decreased O2 carrying capacity

Pulmonary Irritation

  • direct tissue injury
  • acute bronchospasm
  • activation of inflammatory cascade
  • oxygen radical and proteolytic enzymes
  • mucosal damage
  • bronchitis
  • mucus plugging
  • pulmonary oedema
  • bronchospasm
  • bronchorrhoea
  • hypoxaemia/raised A-a gradient
  • SIRS

CLINICAL FEATURES

  • events: enclosed space, explosion, LOC, toxic gases, did you breathe fire, voice changes
  • burns in face, especially around mouth/nose
  • singed nasal hair
  • carbonaceous sputum
  • nasal deposits
  • soot, charring, mucosal erythema/oedema/blistering/necrosis
  • voice changes/hoarseness
  • respiratory distress: hypoxaemia, raised A-a gradient, stridor, wheeze, tachypnoea, dyspnoea
  • high CO levels – might look ‘cherry red’
  • CN: bitter almond odour
  • CO and CN toxicity: lactic acidosis, high SvO2, mental confusion, hypotension

INVESTIGATIONS

  • CXR: diffuse atelectasis, pulmonary oedema, bronchopneumonia (not reliable investigation however)

MANAGEMENT

Prehospital

  • minimise exposure time
  • high flow O2

Inhospital

Airway

  • proportional to severity
  • acutely compromised airway: RSI, smaller ETT +/- surgical airway
  • less severe: RSI or AFOI
  • not compromised: nasal endoscopy, have low threshold for elective intubation
  • leave tube uncut
  • tie tube firmly (wire to teeth)
  • elevate head (decreases oedema)
  • adrenaline and steroids (controversial)

Breathing

  • high flow O2 for 6 hours and until CO levels return to normal
  • bronchospasm: B2 agonists (multiple benefits – bronchodilation, anti-inflammatory, improves airspace fluid clearance and stimulates mucosal repair)
  • humidification
  • NAC and heparin nebulisers (5000U heparin + 3mL of 20% NAC Q4 hrly for 7 days – reduced reintubation and mortality in children)
  • aggressive toileting
  • suction
  • cultures
  • protective lung ventilation strategy: low volume, high PEEP, permissive hypercapnia
  • HFOV
  • ECMO

Circulation

  • no good data
  • tendency to avoid increased fluids
  • should be guided by urine output and haemodynamic parameters
  • use dynamics parameters (pulse pressure variation, fluid responsiveness)
  • early albumin after 24 hours

Carbon Monoxide Toxicity

  • 100% oxygen
  • rapid transport to a hyperbaric centre

Cyanide Toxicity

  • sodium thiosulphate -> produces metHb which can bind CN and allows metabolism by liver enzymes
  • hydroxocobalamin (vitamin B12) -> actively binds CN and allows renal elimination

Other Experimental Therapies

  • nebulised heparin + antithrombin
  • high dose IV heparin
  • IV tPA
  • anti-inflammatories
  • NO inhibitors
  • antioxidants (nebulized vitamin E)
  • methylprednisolone
  • phenytoin (for anti-inflammatory properties)
  • endothelin-1 receptor antagonist (tezosentan)
  • nebulized deferoxamine + pentastarch complex
  • APC
  • decontamination of lungs with amphorteric, hypertonic chelating agents

References and Links


CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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