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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Question 1Infectious DiseaseMedium
A 2-year-old boy presents with 3 days of barky cough, inspiratory stridor, and low-grade fever following an upper respiratory infection (URI). He is in mild respiratory distress, interactive, not drooling. SpO2 is 97%. CXR shows subglottic narrowing (steeple sign). What is the most appropriate treatment?
AHeliox (helium-oxygen) therapy
BOral dexamethasone single dose
CIntravenous ampicillin-sulbactam
DNebulized albuterol
ECool humidified mist therapy
Reveal answer & full explanation
Correct answer: B — Oral dexamethasone single dose
AHeliox (helium-oxygen) therapy
BOral dexamethasone single dose✓
CIntravenous ampicillin-sulbactam
DNebulized albuterol
ECool humidified mist therapy
Why Oral dexamethasone single dose is correct
Croup (laryngotracheobronchitis) is caused by parainfluenza virus and presents with barky (seal-like) cough, inspiratory stridor, and steeple sign on CXR
Occurs in children 6 months to 6 years
Dexamethasone 0.6 mg/kg PO/IM as a single dose reduces subglottic edema and is first-line treatment
Why the others are wrong
Intravenous ampicillin-sulbactam — antibiotics are not indicated for viral croup
Cool humidified mist therapy — randomized trials and a Cochrane review show humidified air does not improve croup scores or reduce admissions, so it is no longer recommended; corticosteroids are the evidence-based therapy
Nebulized albuterol — not effective for croup, which is a subglottic process, not bronchospasm
Heliox (helium-oxygen) therapy — a low-density helium-oxygen mixture that eases turbulent airflow and is sometimes used as a temporizing adjunct in severe croup with impending respiratory failure; this child has mild croup, interactive with an SpO2 of 97%, so a single dose of dexamethasone is the treatment and heliox adds nothing
Additional high-yield points
Nebulized racemic epinephrine is used for moderate-to-severe croup (stridor at rest, retractions)
Epiglottitis (caused by H. influenzae) presents with high fever, drooling, and tripod position — a distinct emergency
Question 2PulmonaryMedium
A 3-year-old has a barky cough, inspiratory stridor only when agitated, and hoarseness after 2 days of rhinorrhea. He is not drooling and appears nontoxic. Which of the following is the most appropriate treatment?
ANebulized racemic epinephrine
BSingle-dose oral dexamethasone
COral amoxicillin therapy
DHumidified cool mist therapy
ENebulized albuterol treatments
Reveal answer & full explanation
Correct answer: B — Single-dose oral dexamethasone
ANebulized racemic epinephrine
BSingle-dose oral dexamethasone✓
COral amoxicillin therapy
DHumidified cool mist therapy
ENebulized albuterol treatments
Why Single-dose oral dexamethasone is correct
Croup is viral subglottic inflammation; a single dose of dexamethasone reduces edema and is recommended across all severity levels.
It shortens symptoms, decreases return visits, and lowers the need for further intervention.
This child has mild croup (stridor only with agitation, nontoxic), so dexamethasone alone is appropriate; nebulized epinephrine is added for stridor at rest or moderate-to-severe distress.
Why the others are wrong
Nebulized racemic epinephrine — Reserved for stridor at rest or moderate-to-severe distress; this child has stridor only with agitation, so steroid therapy alone is sufficient and epinephrine adds rebound and observation burden.
Oral amoxicillin therapy — Croup is viral, so antibiotics provide no benefit (antibiotic-reflex trap).
Nebulized albuterol treatments — Albuterol relaxes lower-airway smooth muscle and does nothing for fixed subglottic edema (misapplied wheeze therapy).
Humidified cool mist therapy — mist tents and humidified air were a long-standing traditional croup remedy, but randomized trials show no improvement in croup scores, so humidification is not recommended and does not replace the corticosteroid every severity level should receive (outdated-remedy trap).
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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)
CMAJ 2013 — Croup in children (Bjornson and Johnson, CMAJ 2013;185:1317-1323)
Westley Score — Nebulized Racemic Epinephrine by IPPB for the Treatment of Croup (Westley et al., Am J Dis Child 1978)
Lancet Review — Croup (Bjornson and Johnson, Lancet 2008;371:329-339)
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