Key Facts

Croup is one of the most common causes of acute upper airway obstruction in children. It is almost always a benign, self-limiting condition. Oral dexamethasone has revolutionised management, significantly reducing the need for hospitalisation.

Epidemiology

Croup affects approximately 3-5% of children in the first 2 years of life. ~5% of affected children attend ED. Only ~1-5% of those seen in ED require admission. Peak incidence: Autumn/winter. Male:female ratio ~1.5:1.

Aetiology

• Parainfluenza (types 1 and 3): ~75% of cases
• RSV, influenza A and B, adenovirus, rhinovirus
• Spasmodic croup: Recurrent episodes without viral prodrome; possible allergic/atopic component

Pathophysiology

Viral infection causes inflammation, oedema, and mucus production in the subglottic region (narrowest part of the paediatric airway). The subglottic region is surrounded by the rigid cricoid cartilage, so even mild oedema causes significant narrowing. Airflow through the narrowed airway produces the characteristic inspiratory stridor. The barking cough results from vibration of the inflamed vocal cords.

Typical Course

• Day 1-2: Coryzal prodrome — rhinorrhoea, mild fever, sore throat
• Day 2-3: Onset of barking cough, hoarse voice, inspiratory stridor
• Worse at night: Symptoms characteristically worsen in the evening/overnight
• Duration: 2-7 days; peak severity usually on night 2-3

Severity Assessment (Westley Score)

• Mild: Barking cough, no stridor at rest, no/mild recession
• Moderate: Stridor at rest, visible recession, no agitation
• Severe: Stridor at rest, marked recession, agitation/lethargy
• Impending failure: Reduced consciousness, minimal stridor (indicates failing ventilation), cyanosis

Red Flags

• Stridor at rest with agitation — severe croup, needs nebulised adrenaline
• Drooling, toxic appearance, no barking cough — think epiglottitis
• Not responding to dexamethasone and adrenaline — consider alternative diagnosis (bacterial tracheitis, foreign body, retropharyngeal abscess)
• Recurrent croup (>2 episodes/year) — consider underlying subglottic stenosis or haemangioma

Bedside

• Clinical diagnosis: Do NOT distress the child with investigations
• SpO2: Monitor — desaturation is a late sign
• Westley croup score: Grade severity

Bloods

• NOT routinely needed — clinical diagnosis

Imaging

• AP neck X-ray: 'Steeple sign' (subglottic narrowing) — rarely needed; do NOT delay treatment for imaging
• Lateral neck X-ray: If epiglottitis suspected ('thumb sign')

Special Tests

• NPA: Only if atypical or influenza season (guide antiviral therapy)
• Direct laryngoscopy: If recurrent croup or diagnostic uncertainty — subglottic stenosis, haemangioma

All Severities

• Oral dexamethasone 0.15mg/kg (single dose; max 12mg) — effective within 2-4 hours; lasts 24-48 hours
• Alternative: Prednisolone 1-2mg/kg if dexamethasone unavailable

Mild Croup

• Dexamethasone and discharge with safety-net advice
• Parent education: Sit upright, comfort child (crying worsens symptoms), cool night air may help

Moderate Croup

• Dexamethasone
• Observe for 2-4 hours after treatment
• Discharge if improving; admit if not

Severe Croup

• Nebulised adrenaline 5mL 1:1000 — rapid effect (within 10-30 min); wears off in ~2 hours; observe for minimum 2 hours for rebound
• Oxygen if SpO2 <92%
• Dexamethasone (if not already given)
• Admit: Monitor in resuscitation area/HDU
• Repeat adrenaline if symptoms recur
• Intubation: Rarely needed; by experienced anaesthetist; use ETT 0.5-1mm smaller than normal

Referral Criteria

• Severe croup not responding to adrenaline — anaesthetics/PICU
• Recurrent croup (>2 episodes/year) — ENT for airway assessment
• Suspected bacterial tracheitis or epiglottitis — emergency management

• Self-limiting: Most children recover within 2-7 days
• Hospitalisation: Only 1-5% of ED attenders
• Intubation: <1% of hospitalised children
• Mortality: Extremely rare in developed countries (<0.5 per 100,000)
• Recurrent croup: ~5% have recurrent episodes; may be associated with atopy or underlying airway abnormality

Westley Croup Score

Mild 0-2; Moderate 3-5; Severe 6-11; Impending failure ≥12.

Croup vs Epiglottitis