Croup

Overview

Croup (laryngotracheobronchitis) is a viral illness causing subglottic inflammation and oedema, producing a barking cough, inspiratory stridor, and hoarse voice. It is the most common cause of acute upper airway obstruction in children.

Presentation

•1-2 day coryzal prodrome followed by nocturnal onset of symptoms

•Barking cough - hallmark; seal-like or brassy

•Hoarse voice - laryngeal mucosal oedema

•Inspiratory stridor - turbulent flow through narrowed subglottis

•Low-grade fever

•Symptoms worse at night and with agitation (increased effort worsens dynamic obstruction)

Severity assessment
FeatureMildModerateSevere
Stridor at restNoYesMarked
RecessionNone/minimalIntercostal ± sternalSignificant
Child's demeanourComfortable, interactiveMild agitationMarked agitation or altered consciousness, pallor/cyanosis, fatigue
SpO2MaintainedMaintainedImpending respiratory failure

Feature	Mild	Moderate	Severe
Stridor at rest	No	Yes	Marked
Recession	None/minimal	Intercostal ± sternal	Significant
Child's demeanour	Comfortable, interactive	Mild agitation	Marked agitation or altered consciousness, pallor/cyanosis, fatigue
SpO2	Maintained	Maintained	Impending respiratory failure

🚨
Toxic appearance, drooling, tripod position, absent cough, rapid onset = NOT croup. Consider epiglottitis or bacterial tracheitis - do NOT examine the throat; escalate immediately.

Investigations

•Clinical diagnosis - no routine tests needed in typical mild-moderate croup

•Pulse oximetry - continuous monitoring in moderate-severe disease

•AP neck/chest X-ray - if diagnosis uncertain; classical finding is the 'steeple sign' (subglottic narrowing) - neither sensitive nor specific

Management

All severity · Minimise distress
1Avoid unnecessary interventions that upset the child - agitation worsens dynamic obstruction
2Keep child with parent in comfortable position
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Mild croup
Single oral dose dexamethasone 0.15 mg/kg - can be managed at home with safety-net advice
Moderate croup
Dexamethasone 0.15 mg/kg orally; monitor with pulse oximetry; observe in ED
Severe croup / impending respiratory failure
Dexamethasone 0.15 mg/kg + nebulised adrenaline (epinephrine) - buys time; effect is temporary so monitor closely. Intubation required in 1-3% of severe cases. Call anaesthetics/ENT early.

💡
Dexamethasone reduces inflammatory subglottic oedema. A single oral dose is as effective as nebulised budesonide and more convenient. Effect begins within 30-60 minutes and lasts 24-48 hours.

Complications

•Respiratory failure - most serious; progressive subglottic oedema

•Bacterial tracheitis - secondary *Staphylococcus aureus* infection; high fever, toxic appearance, rapid deterioration despite croup treatment

•Pneumonia - secondary bacterial lower respiratory tract infection

•Death - very rare; ~1 in 30,000

Prognosis

•Symptoms typically resolve within 48 hours (up to one week in some cases)

•Mild croup is self-limiting; dexamethasone shortens time to resolution

•Intubation required in only 1-3% with impending respiratory failure; death exceedingly rare

Key Background

•Age: 6 months - 3 years; peak at 18 months

•Cause: parainfluenza virus (types 1 and 2) - ~75% of cases; also RSV, influenza, adenovirus

•Seasonal: autumn and early winter

💡
Subglottic narrowing is critical in toddlers - Poiseuille's law means a 1 mm reduction in diameter reduces cross-sectional area by ~75%, causing dramatic rise in airway resistance.