Emergency Medicine · Pulmonary Injury
The facts most likely to be tested
Early endotracheal intubation is indicated for patients with signs of upper airway obstruction, such as stridor, hoarseness, or oropharyngeal burns.
Carbon monoxide (CO) poisoning is the most common cause of death in the early phase of smoke inhalation and must be treated with 100% high-flow oxygen.
Fiberoptic bronchoscopy is the gold standard for the definitive diagnosis of inhalation injury and assessment of the tracheobronchial tree.
Cyanide toxicity should be suspected in patients with smoke inhalation who present with altered mental status, lactic acidosis, and anion gap metabolic acidosis despite adequate oxygenation.
Pulse oximetry is unreliable in carbon monoxide poisoning because carboxyhemoglobin absorbs light at the same wavelength as oxyhemoglobin, resulting in a falsely normal SpO2.
Hydroxocobalamin is the preferred antidote for cyanide poisoning due to its favorable safety profile compared to sodium thiosulfate.
Arterial blood gas (ABG) analysis is required to calculate the carboxyhemoglobin level via co-oximetry, as standard pulse oximetry cannot distinguish between the two.
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A 34-year-old male is brought to the emergency department after being rescued from a house fire. He is confused and has soot around his mouth and nostrils. Physical examination reveals hoarseness and stridor upon inspiration. His pulse oximetry reads 99% on room air, but he is tachypneic with a respiratory rate of 28/min. An arterial blood gas shows a pH of 7.22 and a lactate of 9.5 mmol/L.
What is the most appropriate next step in management?
Endotracheal intubation
The patient exhibits signs of impending airway compromise (stridor, hoarseness, oropharyngeal burns), necessitating immediate airway protection via intubation before edema worsens.
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Etiology / Epidemiology
Occurs in enclosed space fires; suspect in patients with facial burns or singed nasal hairs.
Clinical Manifestations
Look for sooty sputum, stridor, and cherry-red skin (CO poisoning).
Diagnosis
Fiberoptic bronchoscopy is the gold standard; check carboxyhemoglobin >10%.
Treatment
Provide 100% humidified oxygen; intubate early if airway edema is suspected.
Prognosis
Airway obstruction is the #1 cause of early death; monitor for ARDS.
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Epidemiology & Etiology
High risk in victims of enclosed space fires or industrial accidents. Suspect in any patient with altered mental status or facial burns found at a fire scene. Mortality is significantly increased by the presence of concomitant thermal burns.
Pertinent Anatomy
Injury is divided into supraglottic (thermal) and subglottic (chemical) damage. The larynx acts as a protective barrier, but small particles reach the bronchioles and alveoli.
Pathophysiology
Thermal injury causes upper airway edema, while chemical inhalation (e.g., hydrogen cyanide, CO) causes cellular hypoxia. CO binds to hemoglobin with 200x affinity of oxygen, causing a left-shift in the oxyhemoglobin dissociation curve. Cyanide inhibits cytochrome oxidase, halting aerobic metabolism.
Clinical Manifestations
Classic signs include sooty sputum, hoarseness, and singed nasal hairs. Stridor is a red flag for impending airway obstruction. Patients may present with cherry-red skin, though this is rare; altered mental status is a more reliable indicator of systemic toxicity.
Diagnosis
Fiberoptic bronchoscopy is the gold standard for diagnosing inhalation injury. Obtain carboxyhemoglobin levels; levels >10% confirm CO poisoning. Pulse oximetry is unreliable as it cannot distinguish between oxyhemoglobin and carboxyhemoglobin.
Treatment
Administer 100% humidified oxygen via non-rebreather mask immediately. Intubate early if there is evidence of airway edema or respiratory distress, as the airway can close rapidly. Use hydroxocobalamin for suspected cyanide toxicity; avoid prophylactic antibiotics.
Prognosis
Airway obstruction is the leading cause of early mortality. Survivors are at high risk for ARDS and secondary pneumonia. Close monitoring of ABGs and serial pulmonary exams is mandatory.
Differential Diagnosis
Carbon Monoxide Poisoning: normal PaO2, elevated carboxyhemoglobin
Cyanide Toxicity: metabolic acidosis with high lactate
Thermal Airway Burn: localized to oropharynx/larynx
Acute Respiratory Distress Syndrome: bilateral infiltrates on CXR
Pulmonary Contusion: history of blunt chest trauma