Inhalational-Injury

Inhalational Injury

Inhalation Injury: Pathogenesis and Complications
Smoke inhalation
Suspect if patient found unconscious, history of fire in a confined space and presence of facial burns.
Inhalation of carbon monoxide (CO)
CO binds more strongly to hemoglobin than does O2
↑ carboxyhemoglobin in blood, ↓ free hemoglobin available to bind O2 in the lungs
Hypoxemia
↓ O2 delivered to tissues
Potentially permanent CNS dysfunction
Authors: Marshall Thibedeau, W Fraser Hill Reviewers: Spencer Yakaback, Tony Gu, Yan Yu*, Michael Liss*, Duncan Nickerson* * MD at time of publication
Convective heat transfer from smoke in upper airway
Supraglottic Thermal injury
Pharynx mucosal membrane integrity disrupted
Cell lysis and necrosis
Local release of inflammatory substances
↑ vascular permeabilityà edema of tissues in upper airway
Dry/red mucous membranes
Carbonaceous sputum Singed nasal hairs
Inhalation of products of combustion
Tracheobronchial exposure to chemical irritants
Chemical Injury to upper and lower respiratory tract
Inhibition of cytochrome c oxidase
↓ mitochondrial respiratory chain function
Inhalation of plastic combustion products
Inhalation of cyanide
Cyanide binds to mitochondrial cytochrome oxidase a3 with high affinity
Direct cell damage
Lower respiratory tract cilia damage
↓ mucus clearance from alveoli
↓ surfactant
↓ lung compliance
Vasomotor & sensory nerve stimulation
Neuropeptide release
Impaired oxidative phosphorylation and cellular energy production
Cellular dysfunction in high metabolic tissues (muscle, heart, brain)
Atelectasis (collapsed alveoli)
↑ airway exudates
Reactive Inflammation & bronchoconstriction
Ventilation-perfusion mismatch (regions of lung not effectively ventilated, despite being well-perfused by blood)
Hypoxemia
Upper airway obstruction
↑ risk of infection
Impaired heart function
Muscle Weakness
Impaired brain function
Anxiety
Headache
Decreased level of consciousness
Seizures
Vocal cord edema
Hoarseness
Carbon Monoxide Treatment: 100% O2
Transient hypertension and tachycardia
Over time: Bradycardia, hypotension, cardiac arrest
Oropharynx edema
Stridor
↑ partial pressure of O2 in arteries
↑ dissociation rate of carbon monoxide (competitive inhibitor of O2 for hemoglobin)
↓ carboxyhemoglobin half life from 4 hours to 1 hour
Treatment: Intubation and ventilation
Cyanide Treatment: Hydroxocobalamin
Cobalt ion of compound binds cyanide molecules
Cyanocobalamin (Vitamin B12) formed
Excreted renally
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published November 10, 2019 on www.thecalgaryguide.com