• Clinical science

Croup (Laryngotracheitis…)

Abstract

Croup (laryngotracheitis) is one of the most common infectious pediatric emergencies seen in winter. Commonly caused by the parainfluenza virus, croup is characterized by inflammation of the larynx and trachea. The clinical presentation varies depending on the severity of airway obstruction, but typically includes a barking cough, hoarse voice, and inspiratory stridor, all of which tend to occur at night. In moderate to severe cases, respiratory distress with subcostal and intercostal retractions occurs. Croup is primarily a clinical diagnosis, although a chest x-ray may be used to support diagnosis; laboratory tests and pulse oximetry help assess the severity of disease. In mild cases, treatment aims at alleviating symptoms and involves cold, moist air, calming the child, and corticosteroids. Moderate to severe cases require racemic epinephrine. Complications are rare: in cases of respiratory insufficiency, supplemental oxygen is necessary or even sedation and intubation. The prognosis of uncomplicated croup is good, with complete recovery occurring within seven days of onset.

Epidemiology

  • Peak incidence: 6 months to 3 years
  • Most common in fall and winter

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[1]

Clinical features

Prodromal phase

  • Duration: 1–2 days
  • Presentation

Laryngotracheal inflammation phase

  • Duration: 2–7 days
  • Presentation
    • Symptoms of croup primarily occur during the late evening/night.
    • Mild: barking cough, hoarseness, and mild inspiratory stridor due to subglottic narrowing
    • Moderate: dyspnea at rest, pronounced thoracic retractions, pallor, tachycardia > 160/min
    • Severe
      • Severe tachydyspnea at rest with increasing respiratory failure, cyanosis, hypoxemia, bradycardia, and altered mental status.
      • May result in pulsus parodoxus secondary to upper airway obstruction
    • Infants may become agitated as a result of breathing difficulties → worsens agitation and obstruction → in severe cases, exhaustion leads to the infant being unable to breathe on his or her own.

References:[1][3][4]

Diagnostics

Croup is primarily a clinical diagnosis, but imaging may be considered in mild cases of suspected croup. Other tests (e.g., pulse oximetry, blood gas analysis) help to assess the severity of disease. Identification of the viral pathogen is rarely necessary.

  • Based on clinical findings (see “Symptoms/clinical findings” above)
  • Pulse oximetry
  • X-ray of chest and neck: helps to verify subglottic narrowing, usually called the “steeple sign
  • In suspected cases of respiratory insufficiency: blood gas analysis (BGA)
  • If pneumonia or bacterial tracheitis is suspected: CBC
  • PCR: To identify the viral pathogen in tissue (e.g., nasopharyngeal washing)

References:[1][3][5]

Differential diagnoses

Croup (subglottic laryngitis; laryngotracheitis) Epiglottitis (supraglottic laryngitis)

Laryngeal diphtheria

Foreign body (FB) aspiration
Cause
  • Accidental aspiration of a foreign body (e.g., nuts, raisins, seeds, pieces of toys)
Onset
  • Slow: 12–48 hours
  • Sudden: 4–12 hours
  • Initially slow, then sudden onset of symptoms after 4–5 days
  • Sudden
  • If the initial aspiration and choking episode is not witnessed, onset of symptoms (persistent or recurrent cough) days or weeks later
General condition
  • Does not appear toxic
  • Toxic appearance (infectious state with lethargy, poor perfusion, cyanosis, hypo- or hyperventilation), drooling, upright position with extended neck
  • Toxic appearance, possible swollen neck
Cough
  • Barking
  • Absent
  • Barking
  • Choking
Voice
  • Hoarse
  • Muffled
  • Hoarse
  • Hoarseness or inability to speak indicate a laryngotracheal FB
Difficulty swallowing/drooling
  • Absent
  • Present
  • Present
  • Depends on the location of the FB
X-ray findings
  • Most FB are radiolucent; focal overinflation of the distal lung may be visible
  • Approx. 16% of FB in larynx or trachea and 60% in the right lung
Response to inhalators
  • Mild croup: improvement after cool mist inhalation
  • Moderate to severe croup: improvement after epinephrine inhalation
  • No improvement
  • No improvement
  • No improvement
Additional
  • Removal of FB via rigid bronchoscopy
  • Heimlich maneuver if the child is in respiratory distress and cannot speak or cry

Others

  • Asthma/obstructive bronchitis: asthma is characterized by intrathoracic narrowing, which leads to expiratory stridor. Croup, on the other hand, is characterized by extrathoracic narrowing, which leads to inspiratory stridor!
  • Pneumonia: : No inspiratory stridor; mainly a productive cough, high fever, rales (bubbling sounds)

Laryngomalacia

  • Epidemiology
    • Most common cause of congenital stridor
    • Symptoms begin within the first 2 months of life and peak at 6–8 months
  • Pathophysiology: congenital abnormality of laryngeal cartilage → increased laxity and collapse of supraglottic structures during inspiration → airway obstruction
  • Clinical features
    • Usually happy and thriving infants
    • Inspiratory stridor: worsens in supine position, during crying; , upper respiratory tract infections, agitation, and feeding
    • Reflux may be present
    • Failure to thrive and sleep-disordered breathing in severe cases
  • Diagnosis: flexible laryngoscopy: collapse of supraglottic structures during inspiration and omega-shaped epiglottis
  • Treatment

References:[6][7][8][5][9][10][11]

The differential diagnoses listed here are not exhaustive.

Treatment

Severity Treatment
Mild croup
  • Decrease infant's anxiety
  • Cool mist inhalation
  • Placing infant to sleep in an upright position
  • Breathing cool air at night (especially in the winter) helps to soothe symptoms
  • Dexamethasone (0.15 mg/kg)
    • Reduces airway swelling within 6 hours
    • Long-lasting effect
    • Oral syrup, IV or IM injection
Moderate to severe croup

Intubation in severe croup is difficult due to subglottic narrowing → anesthesiologist required!

References:[6][3][12]

Complications

References:[3]

We list the most important complications. The selection is not exhaustive.

Prognosis

  • The prognosis in uncomplicated cases is good, with full recovery.
  • Parents should be aware that croup tends to recur.
    • Most often within a week after recovery
    • If croup recurs within the peak incidence age (six months to three years), airway abnormalities should be suspected.
    • If croup recurs outside the peak incidence age, atopic conditions, airway lesions or gastroesophageal reflux should be suspected.

References:[3]