What is the appropriate management, including medication dosing and supportive care, for an adult presenting with moderate to severe croup (prominent inspiratory stridor at rest, marked suprasternal or intercostal retractions, and agitation)?

Management of Croup in Adults

Critical Recognition: Croup in Adults is Rare and Requires Different Considerations

Adult croup is an uncommon presentation that demands immediate airway assessment and aggressive corticosteroid therapy, as the adult airway anatomy makes obstruction potentially more dangerous than in children.

The provided evidence focuses almost exclusively on pediatric croup management. However, the fundamental pathophysiology—viral-induced laryngotracheal inflammation causing upper airway obstruction—remains similar across age groups, allowing extrapolation of treatment principles with important caveats for adult anatomy and physiology.

Immediate Assessment and Supportive Care

Airway Evaluation

• Assess for impending airway compromise by evaluating the degree of stridor, work of breathing (suprasternal and intercostal retractions), oxygen saturation, and mental status 1, 2, 3
• In moderate-to-severe presentations (prominent inspiratory stridor at rest, marked retractions, agitation), prepare for potential intubation, as adults have less compliant airways and smaller reserve than children 1, 3
• Avoid direct laryngoscopy or instrumentation unless absolutely necessary, as manipulation can precipitate complete airway obstruction 4, 2

Oxygen and Monitoring

• Administer supplemental oxygen to maintain SpO₂ >90% (>95% if cardiac comorbidities exist), similar to asthma exacerbation management 5
• Continuous pulse oximetry and frequent reassessment are essential given the risk of rapid deterioration 1, 3

Primary Pharmacologic Management

Corticosteroids: First-Line Therapy

Dexamethasone is the cornerstone of treatment and should be administered immediately to all adults with croup, regardless of severity.

• Dosing: Administer dexamethasone 0.6 mg/kg intramuscularly or intravenously (maximum practical adult dose typically 10-16 mg) as a single dose 1, 4, 2, 6, 3
• The 0.6 mg/kg dose is critical—lower doses have proven ineffective in pediatric studies and should not be used 4
• Onset of action: Expect clinical improvement approximately 6 hours after administration; symptoms typically improve within 24-48 hours 4, 2
• Oral alternative: If the patient can tolerate oral medication and is not in severe distress, oral dexamethasone at the same dose (0.6 mg/kg) is equally effective 1, 2, 3
• Oral prednisone at an equivalent dose may be considered, though dexamethasone is preferred due to longer duration of action 4

Nebulized Epinephrine: For Moderate-to-Severe Cases

In adults presenting with marked stridor at rest, significant retractions, and agitation, add nebulized epinephrine immediately alongside corticosteroids.

• Dosing: Administer racemic epinephrine 0.5 mL of 2.25% solution diluted in 3 mL normal saline via nebulizer, or L-epinephrine 5 mL of 1:1000 solution (both are equally effective) 1, 4, 2, 6, 3
• Mechanism: Provides rapid (within minutes) but temporary relief of airway obstruction through α-adrenergic vasoconstriction, reducing mucosal edema 4, 6
• Critical monitoring: Observe the patient for at least 2-3 hours after administration due to risk of rebound airway obstruction as the epinephrine effect wears off (typically 2 hours) 4, 2, 3
• May repeat every 20-30 minutes if needed while awaiting corticosteroid effect 1, 3

Alternative Corticosteroid: Nebulized Budesonide

• Nebulized budesonide 2 mg can be given as an alternative in patients who cannot tolerate oral dexamethasone (e.g., severe vomiting, altered mental status) 1, 6
• However, intramuscular or intravenous dexamethasone is generally preferred in adults with moderate-to-severe disease 1, 3

Therapies NOT Supported by Evidence

Humidified Air and Cool Mist

• Do not rely on humidified air, cool mist, or steam therapy as primary treatment—these interventions are not supported by randomized controlled trial evidence and provide no additional symptom improvement 1, 2, 6, 3
• While maintaining adequate humidity is reasonable supportive care, it should never delay or replace corticosteroid administration 4, 6

Heliox

• Heliox (helium-oxygen mixture) may theoretically reduce work of breathing in upper airway obstruction, but there is insufficient evidence to recommend its routine use 1, 6
• Consider only in refractory cases when standard therapy has failed and intubation is being contemplated 1

Disposition and Monitoring

Observation Period

• All adults receiving nebulized epinephrine must be observed for at least 2-3 hours to monitor for rebound obstruction 4, 2, 3
• Patients with moderate-to-severe croup should be admitted for continued monitoring, as adults may have less predictable courses than children 1, 3

Discharge Criteria

• Consider discharge only if:
  • Stridor has resolved or is minimal at rest
  • No retractions or respiratory distress
  • Normal oxygen saturation on room air
  • At least 2-3 hours have passed since last epinephrine dose without symptom recurrence
  • Patient can tolerate oral intake 2, 3

Return Precautions

• Instruct patients to return immediately for worsening stridor, increased work of breathing, inability to swallow secretions, or altered mental status 2, 3

Differential Diagnosis Considerations

Before confirming croup in an adult, actively exclude more dangerous causes of upper airway obstruction:

• Epiglottitis: More common in adults than children; presents with severe sore throat, drooling, muffled voice, and toxic appearance—requires immediate airway management and antibiotics 4, 2, 3
• Bacterial tracheitis: Purulent secretions, high fever, toxic appearance—requires antibiotics and possible airway intervention 2, 3
• Foreign body aspiration: Sudden onset without prodromal upper respiratory symptoms 2, 3
• Peritonsillar or retropharyngeal abscess: Severe throat pain, trismus, neck swelling 4, 2, 3
• Angioedema: Rapid onset, often with facial or tongue swelling; may require epinephrine and antihistamines 2

Common Pitfalls to Avoid

• Do not use lower doses of dexamethasone (e.g., 0.15 mg/kg)—the 0.6 mg/kg dose is essential for efficacy 4
• Do not discharge patients immediately after epinephrine without the mandatory 2-3 hour observation period 4, 2
• Do not delay corticosteroids while attempting humidified air or other unproven therapies 1, 6
• Do not assume adult croup will follow the benign course typical of pediatric cases—adults may have more severe obstruction due to anatomic differences 1
• Do not forget to consider alternative diagnoses, especially epiglottitis, which is more common in adults and requires different management 4, 2, 3