Viral upper airway infection in young children causing barking cough and stridor.
Also known as: croup, laryngotracheobronchitis, viral croup, spasmodic croup
Overview
Acute viral upper airway infection involving the larynx, trachea, and bronchi (laryngotracheobronchitis), causing subglottic inflammation and edema with the characteristic barking cough, hoarseness, and inspiratory stridor in young children.
Epidemiology
Most common cause of acute upper airway obstruction in children. Peak age 6 months to 3 years (rare after age 6). Boys > girls (~1.5:1). Highest incidence in fall and winter.
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Anatomic subglottic narrowing (any child) — small change in radius dramatically increases resistance
Pathophysiology
Viral infection of upper airway mucosa → inflammation and edema of subglottic larynx and trachea → narrowing of the cricoid ring (narrowest part of pediatric airway) → turbulent airflow producing inspiratory stridor and barking cough. Parainfluenza virus types 1-3 cause ~75% of cases (type 1 most common); RSV, influenza, adenovirus, SARS-CoV-2 also implicated.
Mild dyspnea; respiratory distress in severe cases
Signs / physical exam
Inspiratory stridor (audible without stethoscope)
Suprasternal, intercostal, or subcostal retractions in moderate-severe disease
Hoarse voice, barking cough
Tachypnea, mild hypoxia in severe cases (rare)
Generally non-toxic appearance (distinguishes from epiglottitis)
Differential diagnosis
Epiglottitis — High fever, toxic appearance, drooling, tripod posture, NO cough; thumbprint sign on lateral neck XR; airway emergency
Bacterial tracheitis — High fever, toxic appearance, thick purulent secretions, less responsive to standard croup therapy; staphylococcal/streptococcal; airway intervention often needed
Foreign body aspiration — Sudden choking episode, focal wheeze or stridor; CXR may show unilateral hyperinflation
Westley croup score and matched management approach.
Treatment
First-line
Calm child — avoid agitation (worsens stridor); allow caregiver to hold
Humidified air or mist tents — historically used but lack evidence; comfort measure
Single-dose oral, IM, or IV dexamethasone 0.6 mg/kg (max 16 mg) — first-line for ALL severities (including mild); reduces ED return, duration, and admissions
Alternative oral steroid: prednisolone (less commonly used; shorter half-life)
Nebulized budesonide if unable to tolerate PO dexamethasone (equivalent efficacy)
Moderate-severe disease: ADD nebulized racemic epinephrine 0.5 mL of 2.25% in 2.5 mL NS (or L-epinephrine 5 mL of 1:1000) — rapid airway edema reduction
Observe ≥3-4 hours after nebulized epinephrine (rebound stridor); discharge if no stridor at rest and air entry normal
Supplemental oxygen if hypoxic (uncommon in croup)
Second-line / adjunct
Heliox (helium-oxygen mixture) — controversial; reserved for severe refractory cases
Intubation rarely required (<1%) — use smaller endotracheal tube than expected for age due to subglottic edema
Admit if: persistent stridor at rest after treatment, multiple epinephrine doses, dehydration, social concerns, age <6 months
Antibiotics ONLY if bacterial tracheitis or superimposed infection suspected (NOT for routine croup)
Complications
Respiratory failure requiring intubation (rare with appropriate treatment)
Bacterial tracheitis (rare but life-threatening — high fever, toxic, thick secretions)
Post-extubation subglottic stenosis (if intubated and traumatic)
Single-dose dexamethasone 0.6 mg/kg (max 16 mg) is first-line for ALL severities of croup — even mild — and has been the most impactful change in management.
Spasmodic croup: sudden-onset nocturnal stridor without preceding URI symptoms; often allergic/atopic; managed similarly.
Always observe ≥3-4 h after nebulized epinephrine for rebound stridor before discharge.
Croup-like presentation with fever and toxic appearance — think bacterial tracheitis, epiglottitis, or retropharyngeal abscess.
Steeple sign on AP neck XR is specific but insensitive; clinical diagnosis is sufficient.
References
Cochrane Croup — Glucocorticoids for Croup in Children (Gates et al., Cochrane Database Syst Rev 2018)
Pediatrics 2022 — Diagnosis and Management of Croup (Bjornson and Johnson, Pediatrics 2022)
Westley Score — Nebulized Racemic Epinephrine by IPPB for the Treatment of Croup (Westley et al., Am J Dis Child 1978)
NEJM Review — Croup (Bjornson and Johnson, NEJM 2008)
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