Overview
Smoke Inhalation
Quick Reference
Critical Alerts
- Early intubation for airway compromise: Airway edema progresses rapidly
- CO and cyanide toxicity often coexist: Treat empirically
- 100% oxygen for all smoke inhalation: Displaces CO
- Hydroxocobalamin for suspected cyanide: First-line antidote
- Normal SpO2 does not exclude CO poisoning: Pulse ox unreliable
- Burn + Smoke inhalation increases mortality significantly
Indicators for Intubation
| Finding | Action |
|---|---|
| Stridor | Immediate intubation |
| Hoarseness | Strong consideration |
| Facial burns, singed nasal hairs | Anticipate edema |
| Soot in oropharynx | Lower threshold |
| Upper airway edema on scope | Immediate |
| Deteriorating mental status | Secure airway |
Emergency Treatments
| Condition | Treatment |
|---|---|
| CO poisoning | 100% O2 via NRB or intubation; consider HBO |
| Cyanide poisoning | Hydroxocobalamin 5g IV |
| Airway edema | Early intubation |
| Bronchospasm | Nebulized albuterol |
Definition
Overview
Smoke inhalation injury encompasses thermal injury to the upper airway, chemical injury to the tracheobronchial tree and alveoli, and systemic toxicity from carbon monoxide (CO) and hydrogen cyanide (HCN). It is a leading cause of death in fires. Management priorities include airway protection, high-flow oxygen, and treatment of CO and cyanide toxicity.
Types of Injury
| Type | Location | Mechanism |
|---|---|---|
| Thermal | Upper airway | Heat; steam |
| Chemical | Lower airway, alveoli | Combustion products |
| Systemic | Cellular | CO, Cyanide |
Epidemiology
- Leading cause of fire-related deaths
- 50-80% of fire fatalities: Due to smoke inhalation (not burns)
- Inhalation + Burns: Significantly increases mortality
Etiology
Toxic Products of Combustion:
| Toxin | Source | Effect |
|---|---|---|
| Carbon monoxide | Incomplete combustion | Tissue hypoxia |
| Hydrogen cyanide | Plastics, wool, silk | Cellular asphyxiation |
| Acrolein | Wood, paper | Mucosal irritation |
| Ammonia | Nylon, silk | Mucosal injury |
| Chlorine | PVC | Pulmonary edema |
| Particulates | Soot | Lower airway injury |
Pathophysiology
Upper Airway (Thermal Injury)
- Heat usually dissipates in upper airway
- Exception: Steam (high heat capacity) → Reaches lower airway
- Edema develops over hours → Airway obstruction
Lower Airway (Chemical Injury)
- Combustion products cause mucosal injury
- Bronchospasm, mucosal sloughing
- ARDS may develop
Carbon Monoxide
- Binds hemoglobin (COHb) with 200-250× affinity of O2
- Left-shifts O2-dissociation curve
- Tissue hypoxia despite normal PaO2
Cyanide
- Inhibits cytochrome oxidase (mitochondria)
- Blocks cellular respiration
- Lactic acidosis
Clinical Presentation
Symptoms
| Finding | Significance |
|---|---|
| Dyspnea | Airway or pulmonary injury |
| Hoarseness, stridor | Upper airway edema |
| Cough | Mucosal irritation |
| Wheezing | Bronchospasm |
| Confusion, Headache | CO poisoning |
| Altered mental status | CO or cyanide |
History
Key Questions:
Physical Examination
| Finding | Significance |
|---|---|
| Facial burns | High risk for inhalation |
| Singed nasal hairs | Upper airway exposure |
| Soot in nares, mouth | Below glottis exposure |
| Hoarseness, stridor | Upper airway edema |
| Wheezes, rhonchi | Lower airway injury |
| Cherry-red skin | CO (classic but rare) |
| Hypotension, acidosis | Cyanide |
Enclosed space exposure
Common presentation.
Duration of exposure
Common presentation.
Loss of consciousness at scene
Common presentation.
Type of materials burning (plastics, synthetics)
Common presentation.
Associated burns
Common presentation.
Red Flags
Immediate Airway Management
| Finding | Action |
|---|---|
| Stridor | Intubate immediately |
| Progressive hoarseness | Intubate early |
| Facial/Neck burns | Anticipate edema |
| Upper airway edema on bronchoscopy | Intubate |
| Mental status change | Secure airway |
Cyanide Suspicion
| Finding | Action |
|---|---|
| Unexplained severe acidosis (lactate >0) | Hydroxocobalamin |
| Hypotension + Acidosis | Hydroxocobalamin |
| Cardiac arrest after fire | Hydroxocobalamin |
Diagnostic Approach
Laboratory
| Test | Finding |
|---|---|
| COHb level | Elevated (co-oximetry required) |
| ABG | Metabolic acidosis (cyanide), PaO2 may be normal |
| Lactate | Elevated (>0 suggests cyanide) |
| Cyanide level | Often not available rapidly |
| CBC | Baseline |
| BMP | Electrolytes, renal function |
Note: SpO2 unreliable (reads falsely normal with COHb)
Imaging
Chest X-ray:
| Finding | Interpretation |
|---|---|
| Often normal initially | Injury may not be visible |
| Pulmonary edema | ARDS developing |
| Atelectasis | Mucus plugging |
Bronchoscopy
- Direct visualization of airway
- Edema, erythema, soot, mucosal sloughing
- Helps predict severity
Treatment
Principles
- Secure airway early: Edema progresses
- 100% oxygen for all: Treats CO and maximizes O2 delivery
- Hydroxocobalamin for cyanide: Empiric if suspected
- Supportive care: Bronchodilators, fluids, monitoring
Airway Management
Indications for Intubation:
| Finding | |
|---|---|
| Stridor, hoarseness | |
| Significant facial burns | |
| Upper airway edema | |
| Deteriorating mental status | |
| Anticipated clinical course |
Technique:
- Use larger ETT if possible (can downsize later)
- Video laryngoscopy may help visualization
- Avoid succinylcholine if burn >24 hours (hyperkalemia)
Carbon Monoxide Treatment
| Intervention | Details |
|---|---|
| 100% O2 | Via NRB or ETT |
| Half-life of COHb | Room air: 4-5 hours; 100% O2: 60-90 min; HBO: 20-30 min |
| Hyperbaric oxygen | Consider if COHb >5%, LOC, cardiac ischemia, pregnancy |
Cyanide Treatment
Hydroxocobalamin (First-Line):
| Dose | Notes |
|---|---|
| 5 g IV over 15 min | May repeat |
| Binds cyanide → Cyanocobalamin (excreted) | |
| Safe; minimal side effects | Skin turns red |
Cyanide Antidote Kit (Alternative):
| Components | Notes |
|---|---|
| Amyl nitrite (inhaled) | Induces methemoglobinemia |
| Sodium nitrite IV | Same |
| Sodium thiosulfate IV | Enhances cyanide excretion |
| Caution | Nitrites worsen CO toxicity |
Bronchospasm
| Agent | Dose |
|---|---|
| Albuterol nebulized | 2.5-5 mg q20min PRN |
| Ipratropium nebulized | 0.5 mg q4-6h |
Supportive Care
| Intervention | Details |
|---|---|
| IV fluids | Burns may need resuscitation |
| Monitor | Serial exams, ABG, COHb |
| Bronchoscopy | Consider for soot clearance |
| Prophylactic intubation | If transfer needed and edema expected |
Disposition
Admission Criteria
- Significant smoke exposure
- Elevated COHb
- Respiratory symptoms
- Suspected cyanide toxicity
- Burns with inhalation injury
ICU Admission
- Intubated
- Hemodynamic instability
- Severe acidosis
- ARDS
Discharge Criteria
- Brief exposure, minimal symptoms
- Normal mental status
- Normal COHb
- Normal lactate
- Observation × 4-6 hours without deterioration
Referral
| Indication | Referral |
|---|---|
| Burns | Burn center |
| HBO consideration | Hyperbaric center |
| ARDS | Critical care |
Patient Education
Condition Explanation
- "You inhaled smoke which can injure your lungs and cause poisoning from gases like carbon monoxide."
- "We are giving you high-concentration oxygen to help clear the poison."
Prevention
- Working smoke detectors
- Fire escape plan
- Avoid re-entering burning buildings
- Crawl low in smoke (toxins rise)
Quality Metrics
Performance Indicators
| Metric | Target | Rationale |
|---|---|---|
| 100% O2 administered | 100% | CO treatment |
| COHb level obtained | 100% | Diagnosis |
| Early intubation for stridor | 100% | Airway protection |
| Hydroxocobalamin for suspected cyanide | >0% | Empiric treatment |
Documentation Requirements
- Enclosed space exposure
- Duration of exposure
- Airway exam findings
- COHb level
- Treatment and response
- Disposition rationale
Key Clinical Pearls
Diagnostic Pearls
- SpO2 is unreliable in CO poisoning: Use co-oximetry
- Lactate >10 suggests cyanide toxicity
- Airway edema progresses over hours: Early intubation
- Singed nasal hairs + Soot = High-risk airway
- Normal CXR initially: Injury develops later
- Cherry-red color is rare: Do not wait for it
Treatment Pearls
- 100% O2 for all: Reduces COHb half-life
- Early airway if any concern: Edema worsens rapidly
- Hydroxocobalamin is safe: Give empirically if cyanide suspected
- Avoid nitrite kit if CO poisoning also present: Worsens O2 delivery
- HBO for severe CO: LOC, pregnancy, cardiac ischemia, COHb >25%
Disposition Pearls
- Admit for significant exposure or symptoms
- ICU for intubated or unstable
- Burns + Inhalation = Burn center transfer
- Observe asymptomatic × 4-6 hours before discharge
References
- Rehberg S, et al. Pathophysiology and treatment of inhalation injury. Burns. 2009;35(1):4-14.
- Weaver LK. Carbon monoxide poisoning. N Engl J Med. 2009;360(12):1217-1225.
- Baud FJ, et al. Elevated blood cyanide concentrations in victims of smoke inhalation. N Engl J Med. 1991;325(25):1761-1766.
- Borron SW, et al. Hydroxocobalamin for severe acute cyanide poisoning by ingestion or inhalation. Am J Emerg Med. 2007;25(5):551-558.
- Mlcak RP, et al. Respiratory management of inhalation injury. Burns. 2007;33(1):2-13.
- American Burn Association. Inhalation Injury Guidelines. 2018.
- Tintinalli JE, et al. Smoke Inhalation. Tintinalli's Emergency Medicine. 9th ed. 2020.
- UpToDate. Smoke inhalation injury. 2024.