Viral Croup (Acute Laryngotracheobronchitis)

I. Introduction & Definition

• Definition: Acute clinical syndrome characterized by a barking cough, hoarseness, inspiratory stridor, and respiratory distress.
• Pathology: Edema of the larynx, trachea, and bronchi (subglottic area is the narrowest part of the pediatric airway).
• Epidemiology:
  • Most common cause of upper airway obstruction in children.
  • Age: 6 months to 3 years (Peak: 2nd year).
  • Season: Late autumn to early winter.

II. Etiology

• Parainfluenza Virus (Types 1, 2, 3): Most common cause (~75%).
• Other Viruses:
  • Influenza A & B.
  • Respiratory Syncytial Virus (RSV).
  • Adenovirus.
  • Human Metapneumovirus.
  • Measles (rare but severe).

III. Clinical Features

Prodrome: 12–72 hours of mild Coryza/URTI (rhinorrhea, mild fever).

Triad of Croup (Progression):

1. Barking Cough: Seal-like, brassy cough.
2. Hoarseness: Due to vocal cord inflammation.
3. Inspiratory Stridor: Harsh, high-pitched sound (worse on agitation).

Physical Signs:

• Respiratory distress: Suprasternal/intercostal retractions.
• Symptoms typically worsen at night.
• Absence of drooling (differentiates from Epiglottitis).

IV. Assessment: Westley Croup Score

Used to classify severity based on 5 parameters.

Severity Classification:

• Mild (Score ≤ 2-3): Occasional barking cough, no stridor at rest, child happy/eating.
• Moderate (Score 4–7): Stridor at rest, retractions present, but no agitation.
• Severe (Score ≥ 8): Significant stridor at rest, marked retractions, agitation/lethargy (hypoxia).
• Life-Threatening: Score >11-12.

V. Diagnosis & Investigations

• Diagnosis: Primarily Clinical.
• X-Ray Neck (AP View):
  • Steeple Sign: Subglottic narrowing of the trachea (resembles a church steeple).
  • Note: X-ray is mainly done to rule out foreign bodies or epiglottitis (Thumb sign) if diagnosis is uncertain.
• Labs:
  • CBC: Mild leukocytosis (Lymphocytic or Neutrophilic).
  • CRP: Usually normal or mildly elevated.

VI. Management

1. General Measures

• Keep Child Calm: Agitation increases oxygen demand and stridor.
• Minimal Handling: Avoid painful procedures (venipuncture) if severe distress.
• Hydration: Oral preferred; IV only if unable to drink/severe distress.

2. Pharmacotherapy

A. Corticosteroids (The Mainstay):

• Reduces laryngeal edema. Effective in mild, moderate, and severe cases.
• Drug: Dexamethasone.
• Dose: 0.15 mg/kg to 0.6 mg/kg (Stat oral/IM/IV).
• Alternative: Nebulized Budesonide (2 mg).

B. Nebulized Adrenaline (Epinephrine):

• Indication: Moderate to Severe Croup (Stridor at rest).
• Mechanism: Vasoconstriction of mucosal arterioles $\to$ decreased edema.
• Dose: L-Epinephrine (1:1000) 0.5 ml/kg (Max 5 ml) nebulized with saline.
• Observation: Patient must be observed for 2–4 hours post-nebulization for "Rebound phenomenon" (return of stridor).

3. Algorithm by Severity

• Mild: Single dose oral Dexamethasone + Home care + Warning signs counselling.
• Moderate: Hospital admission + Oral/IM Dexamethasone + Observe.
• Severe:
  • Hospital admission (ICU/HDU).
  • Oxygen (if SpO2 <92%).
  • Nebulized Adrenaline (repeat every 20-30 mins if needed).
  • IV Dexamethasone.
  • Intubation (rare) if respiratory failure ensues.

VII. Differential Diagnosis

1. Acute Epiglottitis: High fever, toxic, drooling, tripod position (Emergency).
2. Bacterial Tracheitis: "Super-croup" (high fever, toxic, poor response to epinephrine).
3. Foreign Body Aspiration: Sudden onset, history of choking, no fever.
4. Spasmodic Croup: Recurrent, allergic component, no viral prodrome.