Croup

Croup is a spectrum of disease involving the upper airway and sometimes extending into the lung parenchyma (laryngotracheitis, laryngotracheobronchitis, laryngotracheobronchopneuomnitis). The pathogenesis of croup results from infiltration of the subglottic region of the larynx by an infectious pathogen – mostly viral with 80% human parainfluenza viruses, especially type I and III. The infiltration causes erythema, edema, and glandular hypersecretion of the subglottic mucosa.

Symptoms of croup are a low-grade fever with or without upper respiratory infection-like prodrome, a characteristic barking cough, and inspiratory stridor accompanied by varying degrees of respiratory distress. Croup symptoms typically worsen at night.

• Young children between 6 months and 3 years of age
• Most commonly between November and February (consistent with parainfluenza virus epidemics)
• Male predominance in both visits and admission rates at 3:2

• The subglottic mucosa is bound by a complete ring of cartilage. As a result, it cannot expand outward to accommodate for narrowing of the airway. Croup can lead to significant respiratory distress and can make for a potentially difficult airway to manage.
• Physics lesson! Poiseuille’s law states that the increase in airway resistance is inversely proportion to the 4th power of radius which is why even a minimal amount of airway edema leads to an exponential rise in airway obstruction.

Acute febrile stridor includes several can’t miss diagnoses:

• Bacterial tracheitis – URI, high fever, toxic appearance, acute-onset stridor and poor response to epinephrine
• Epiglottitis – High fever, dysphonia, dysphagia, refusal to eat, absence of cough, toxic appearance, drooling, tripod positioning, obtundation (incidence has dramatically decreased with universal immunization against H influenzae type B)
• Retropharyngeal abscess – Fever, neck pain, decreased ROM of neck

In afebrile patients with stridor, consider the following:

• Foreign body aspiration
• Spasmodic croup
• Thermal or caustic injury to the airway
• Angioneurotic edema
• Accidental or intentional strangulation

• Physical Exam
  • ABCs
  • Limit agitation because symptoms can worsen
  • Respiratory Status
    • Mild (no stridor or chest wall retractions)
    • Moderate (stridor and mild chest wall retractions at rest; little to no agitation)
    • Severe (stridor and retractions of sternum; agitation or lethargy)
• Westley Croup Score – Assesses severity
  • Considers 5 clinical characteristics (1) level of consciousness, (2) cyanosis, (3) stridor, (4) air entry, and (5) retractions
  • Useful in clinical research but clinical utility is limited
• Although croup is typically a clinical diagnosis, the classic finding on imaging of a patient with croup is the steeple sign (per Tintinalli’s, steeple sign is absent in up to 50% of cases)

• Corticosteroids – indicated for all patients
  • Dexamethasone 0.6mg/kg IV formulation given PO
    • Several studies have suggested that 0.15mg/kg to 0.3mg/kg is just as effective
  • Budesonide 2.5mg by nebulization can be safely substituted for dexamethasone if a child cannot tolerate oral administration
• Nebulized Epinephrine – indicated when there is stridor at rest
  • Induces vasoconstriction in laryngeal mucosa by stimulating alpha-adrenergic receptors
  • Promotes bronchial smooth muscle relaxation
  • Racemic epinephrine 2.25% (0.5mL in 2.5mL saline)
  • Regular epinephrine 1:1,000 concentration (or 1mg/ml) – 5mL diluted in 2-5mL of saline
  • Up to 2 doses of nebulized epinephrine every 15 to 20 minutes
  • Observe for 2 hours after first nebulized epinephrine
  • 2 doses typically “equals admission”
• Heliox
  • Mixture of helium and oxygen that has similar viscosity but sevenfold lower density than air
  • Thought to reduce flow resistance by creating a less turbulent flow
  • Evidence is limited
• Humidified Air
  • Postulated benefits are decreased viscosity of tracheal secretions as well as mucosal cooling and a subsequent reduction in edema
  • Evidence is limited
• Endotracheal Intubation
  • Last resort for respiratory failure refractory to above interventions
  • Consider using one size smaller ET tube than you would normally use to accommodate airway swelling
  • Consider assistance from ENT and anesthesia

• Patients who improve and no longer have stridor at rest or chest wall retractions
• Reliable patients/family who can follow return precautions for return of stridor or respiratory distress

• General Ward for patients in moderate respiratory distress after steroids and/or those that required nebulized epinephrine x 2
• PICU +/- ENT consult for airway management for patients with signs of severe respiratory failure