Croup

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Croup, also known as laryngotracheobronchitis, is an acute viral respiratory illness that causes inflammation and narrowing of the upper airway, leading to a characteristic barking cough, stridor, and hoarseness. It primarily affects children aged 6 months to 3 years.

Aetiology

Croup is most commonly caused by viral infections, including:

  • Parainfluenza virus: the most common cause.
  • Respiratory syncytial virus (RSV).
  • Influenza virus.
  • Adenovirus.
  • Rhinovirus.

Pathophysiology

The infection causes inflammation of the larynx, trachea, and bronchi, leading to:

  • Swelling of the subglottic area (below the vocal cords).
  • Airway narrowing and obstruction.
  • Increased work of breathing and stridor (inspiratory noise).
  • Characteristic barking cough due to turbulent airflow.

Risk factors

  • Age 6 months to 3 years (peak incidence at 1–2 years).
  • Male gender (slightly more common in boys).
  • Recent upper respiratory tract infection (URTI).
  • Exposure to viral infections in nursery or daycare settings.
  • Autumn and winter seasons.

Signs and symptoms

Symptoms:

  • Barking cough (seal-like).
  • Hoarseness.
  • Fever (low-grade in most cases).
  • Stridor (worse with agitation or crying).
  • Difficulty breathing.

Signs:

  • Inspiratory stridor.
  • Tachypnoea (increased respiratory rate).
  • Subcostal and intercostal recession (increased work of breathing).
  • Cyanosis in severe cases.

Investigations

Croup is primarily a clinical diagnosis, and investigations are rarely needed. Consider the following in severe or atypical cases:

  • Pulse oximetry: to assess oxygen saturation.
  • Neck X-ray: only if there is diagnostic uncertainty (e.g., to exclude epiglottitis). May show the characteristic "steeple sign" (subglottic narrowing).

Management

1. Mild Croup (no stridor at rest):

  • Single dose of oral dexamethasone (0.15 mg/kg): reduces inflammation and symptoms.
  • Parental reassurance: symptoms are self-limiting and usually resolve within 48 hours.

2. Moderate to Severe Croup (stridor at rest, respiratory distress):

  • Oral dexamethasone (0.15–0.6 mg/kg) or nebulised budesonide: reduces airway swelling.
  • Nebulised adrenaline (epinephrine): provides temporary relief of airway obstruction. Monitor closely after administration for recurrence of symptoms.
  • Oxygen therapy: if SpO₂ <92%.

3. General Measures:

  • Keep the child calm to reduce airway obstruction (distress worsens stridor).
  • Avoid unnecessary interventions or agitation.

Referral

Refer to secondary care if any of the following are present:

  • Severe respiratory distress: stridor at rest with significant work of breathing.
  • Cyanosis or SpO₂ <92% despite oxygen therapy.
  • Recurrent episodes requiring nebulised adrenaline.
  • Diagnostic uncertainty: consider epiglottitis or foreign body aspiration.
 
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