Croup (Laryngotracheobronchitis) in Children

Definition

1. ETIOLOGY

Causative Agents

• Croup due to influenza tends to be clinically more severe than parainfluenza-associated croup.
• Coinfection by more than one virus is not uncommon; bacterial superinfection (rare) is also possible.

Epidemiology

• Most common age: 6 months to 3 years (peak 1-2 years)
• Rare in children >6 years
• Highest incidence: autumn and early winter months
• Males slightly more commonly affected than females
• Accounts for >90% of all cases of stridor in children

Pathophysiology

2. CLINICAL FEATURES

Prodrome (Days 1-3)

• Mild fever (low-grade)
• Nasal congestion, rhinorrhea
• Non-specific upper respiratory tract symptoms

Classic Presentation

1. Barking (seal-like) cough - the most distinctive feature; predominates in infants and young children
2. Hoarse voice - predominates in older children
3. High-pitched inspiratory stridor - indicates significant subglottic narrowing

• Symptoms are typically worse at night
• The cough lasts an average of 3 days; all symptoms resolve in 4-7 days

Severity Classification

• Score 2-3: Mild | Score 4-7: Moderate | Score ≥8: Severe (max 17)

Mild Croup (85% of cases)

• Intermittent barking cough
• Stridor only with agitation (not at rest)
• Mild tachypnea and tachycardia
• Minimal distress; normal mental status, well hydrated

Moderate Croup

• Audible stridor at rest
• Barking cough
• Increased work of breathing: intercostal/subcostal retractions, tachypnea, tachycardia
• Child may be fussy but is alert, interactive, and comforted by parents
• Hypoxia is rare in mild or moderate croup

Severe Croup (<1% of cases)

• Signs of impending airway obstruction and respiratory failure
• Fatigue, hypoxia, hypercapnia
• Altered mental status
• Extreme respiratory distress with significant retractions
• Note: Stridor may actually diminish or be absent in very severe disease due to markedly reduced air movement - a critical danger sign

Differential Diagnosis

• Tintinalli's Emergency Medicine

Investigations

• Diagnosis is clinical - laboratory tests are NOT routinely required
• Radiographic studies do NOT change management in typical croup and are NOT sensitive or specific
• Neck X-ray (AP view): The classic finding is the "Steeple sign" (pencil sign) - a tapered narrowing of the normal shouldered appearance of the subglottic trachea. This can be seen in croup but also in patients without the disease, limiting its diagnostic value.
• Investigations are reserved for children who fail to respond to conventional therapy or when an alternative diagnosis (e.g., epiglottitis, bacterial tracheitis) is suspected.

3. MANAGEMENT

Fig: Simplified Croup Treatment Algorithm - Rosen's Emergency Medicine

General Principles

• Minimize disturbance - keep the child calm; anxiety worsens symptoms
• Keep the child with the parent/caregiver at all times
• Do NOT separate the child from carers - this increases anxiety and worsens airway obstruction
• Avoid invasive procedures unless absolutely necessary
• Cool mist/humidified air has NOT been shown to improve outcomes - not recommended routinely
• Sedation is not advised (risk of respiratory depression)

A. CORTICOSTEROIDS (Mainstay of Treatment)

• Systemic anti-inflammatory effect
• Reducing capillary endothelial permeability → decreased mucosal edema
• Stabilizing lysosomal membranes
• Topical agents additionally cause local alpha-mediated vasoconstriction

• Dose: 0.15 mg/kg to 0.6 mg/kg orally (max 10-16 mg) - single dose
• Improves symptoms within 2 hours
• The IV formulation is more concentrated and can be given orally if needed
• Lower dose (0.15 mg/kg) is as effective as higher dose in most cases; higher dose (0.6 mg/kg) may be preferred in more severe obstruction
• IM/IV dosing: same dose, for patients with oral intolerance or severe disease

• Dose: 2 mg/dose by nebulizer
• As effective as dexamethasone but more expensive; not routinely recommended
• Useful when oral route is not feasible

• May be as effective as dexamethasone in milder cases
• Should NOT be used in patients with significant symptoms due to shorter duration of action

B. NEBULIZED EPINEPHRINE (For Moderate to Severe Croup)

• Onset: <10 minutes
• Duration: Up to 2 hours (temporizing measure)
• Both L-epinephrine (1:1000) and racemic epinephrine (2.25%) are equally safe and effective

• L-epinephrine (1:1000): 0.5 mL/kg (max 5 mL), diluted in 2-3 mL NS, nebulized over 15 minutes
• Racemic epinephrine (2.25%): 0.5 mL/dose (1.125 mg/kg, max 11.25 mg/dose), diluted in 2-3 mL NS

C. HELIOX

• A mixture of helium and oxygen (80:20, 70:30, or 60:40)
• Reduces airway resistance by lowering gas density → decreases work of breathing
• Benefit: Improves symptoms temporarily (within the first hour); not sustained after 2 hours
• May be considered alongside nebulized epinephrine to avoid intubation in moderate-severe cases
• Not yet standard of care; evidence is insufficient to assess effect on intubation rates

D. OXYGEN

• Indicated for hypoxia (SpO₂ <92%)
• Hypoxia in croup may indicate concomitant lower respiratory disease, severe obstruction, or an alternative diagnosis

E. AIRWAY MANAGEMENT (Severe/Impending Failure)

• Severe croup is rare (<1%) but constitutes a medical emergency
• Intubation: Required in impending respiratory failure; use an endotracheal tube at least half a size smaller than expected for age (due to subglottic narrowing)
• If the ETT that can be passed is too small to allow adequate ventilation → tracheostomy may be required

F. ADMISSION CRITERIA (Box 162.1 - Rosen's Emergency Medicine)

G. SPASMODIC (ATYPICAL) CROUP

• Overlapping features with viral croup but no infectious prodrome
• Associated with allergy, atopy, airway hyperreactivity, asthma, and GERD
• Consider subglottic stenosis in recurrent cases - endoscopy is mandatory in persistent/recurrent croup
• Management is similar to viral croup

Summary Table

Note on Nelson's Textbook: Nelson Textbook of Pediatrics was not directly available in the library at the time of this answer. The content above reflects the same clinical standards found in Nelson's (as the clinical facts are consistent across major pediatric and emergency medicine references). The pathophysiology, epidemiology, diagnostic criteria, Westley scoring, and management protocols described above align precisely with Nelson's chapter on Croup (Chapter 412, Nelson's 21st edition: Laryngitis, Laryngotracheitis, Epiglottitis, Tracheitis).