9.1 Croup, Epiglottitis, Bronchiolitis, Asthma & Cystic Fibrosis

Pediatric Respiratory Emergencies and Chronic Conditions

Respiratory distress is one of the most common reasons for pediatric emergency visits. A structured approach to evaluating the airway, breathing, and circulation is essential. The pediatric airway is smaller, more compliant, and more easily obstructed by edema or secretions compared to adults. Recognizing the signs of impending respiratory failure—such as altered mental status, severe retractions, and head bobbing—is critical.

Croup (Laryngotracheobronchitis)

Croup is the most common infectious cause of upper airway obstruction in children, typically affecting those aged 6 months to 3 years. It is predominantly caused by the parainfluenza virus, though RSV and adenoviruses can also be implicated. Clinical Presentation: Patients present with a prodrome of upper respiratory symptoms (coryza, low-grade fever), followed by a characteristic "barking" or seal-like cough, hoarseness, and inspiratory stridor. Symptoms often worsen at night or with agitation. Diagnosis: The diagnosis is primarily clinical. If a neck radiograph is obtained (usually to rule out other causes), it may show the classic "steeple sign" (subglottic narrowing), though imaging is not routinely required and should not delay treatment. Management:

• Mild (no stridor at rest): Single dose of oral dexamethasone (0.15 to 0.6 mg/kg) is usually sufficient.
• Moderate/Severe (stridor at rest, severe retractions): Dexamethasone plus nebulized racemic epinephrine. Observe the patient for at least 2-4 hours post-epinephrine to monitor for rebound stridor before considering discharge.

Epiglottitis

Historically caused by Haemophilus influenzae type b (Hib), the incidence of epiglottitis has drastically decreased due to widespread immunization. Currently, Streptococcus pyogenes, S. pneumoniae, and Staphylococcus aureus are more common pathogens in vaccinated populations. Clinical Presentation: It is a life-threatening medical emergency characterized by the abrupt onset of high fever, severe sore throat, and the "4 Ds": drooling, dysphagia, dysphonia, and distress. Children often assume a "tripod" position (leaning forward, neck extended) to maximize airway patency. Diagnosis: Clinical suspicion mandates extreme caution. Do not agitate the child or examine the posterior pharynx with a tongue depressor without a definitive airway management plan (e.g., in the OR), as this can precipitate sudden airway spasm and arrest. A lateral neck X-ray may show the "thumbprint sign" (swollen epiglottis). Management: Secure the airway immediately (endotracheal intubation in a controlled setting). Initiate empiric IV antibiotics (e.g., ceftriaxone plus vancomycin) to cover common bacterial pathogens.

Bronchiolitis

Bronchiolitis is an acute inflammatory illness of the upper and lower respiratory tracts, predominantly affecting infants and children under 2 years of age. Respiratory syncytial virus (RSV) is the most common etiology. Clinical Presentation: Initial symptoms include rhinorrhea and low-grade fever, progressing over 2-3 days to lower respiratory tract signs: tachypnea, wheezing, diffuse crackles, and increased work of breathing (nasal flaring, intercostal and subcostal retractions). Diagnosis: Clinical diagnosis based on age, season (typically winter/spring), and physical findings. Routine chest X-rays (often showing hyperinflation and peribronchial thickening) and viral testing are not recommended for typical, uncomplicated cases. Management: Supportive care is the mainstay of therapy. Maintain adequate hydration and oxygenation (target SpO2 >90-92%). Routine use of bronchodilators, inhaled corticosteroids, and hypertonic saline is not recommended by current guidelines. High-flow nasal cannula (HFNC) or CPAP may be used for moderate to severe respiratory distress. Prophylaxis with palivizumab (an RSV monoclonal antibody) is reserved for high-risk infants (e.g., severe prematurity, hemodynamically significant congenital heart disease).

Pediatric Asthma

Asthma is a chronic inflammatory disorder of the airways characterized by hyperresponsiveness, mucosal edema, and reversible airflow obstruction. Diagnosis: Diagnosis in young children (under 5 years) is often clinical, based on recurrent episodes of wheezing, cough (especially prominent at night), and a positive clinical response to bronchodilators. In older children, spirometry demonstrates reversible obstructive patterns (FEV1/FVC ratio <80%, with >12% improvement after bronchodilator administration). Management (Step-wise Approach):

1. Intermittent: SABA (Short-Acting Beta Agonist) as needed for symptom relief.
2. Mild Persistent: Low-dose Inhaled Corticosteroid (ICS) daily + SABA PRN.
3. Moderate Persistent: Medium-dose ICS OR Low-dose ICS + LABA (Long-Acting Beta Agonist).
4. Severe Persistent: High-dose ICS + LABA + consider oral corticosteroids or targeted biologics (e.g., omalizumab). Acute Exacerbation: Management includes supplemental oxygen, continuous nebulized albuterol, ipratropium bromide, and systemic corticosteroids (oral dexamethasone/prednisone or IV methylprednisolone). Intravenous magnesium sulfate may be considered for severe refractory exacerbations.

Cystic Fibrosis (CF)

CF is an autosomal recessive disorder caused by mutations in the CFTR gene (most commonly the F508del mutation), leading to defective chloride transport across epithelial cells. This results in thick, viscous secretions in multiple organs, particularly the lungs and pancreas. Clinical Presentation:

• Respiratory: Recurrent sinopulmonary infections, chronic productive cough, and progressive bronchiectasis. Early pathogens include Staphylococcus aureus and Haemophilus influenzae; in adolescence and adulthood, Pseudomonas aeruginosa predominates.
• GI/Nutrition: Meconium ileus in neonates, exocrine pancreatic insufficiency (steatorrhea, deficiency of fat-soluble vitamins A, D, E, K), and failure to thrive.
• Reproductive: Bilateral absence of the vas deferens leads to infertility in the vast majority of affected males. Diagnosis: Newborn screening often detects elevated immunoreactive trypsinogen (IRT). The confirmatory gold standard is the quantitative sweat chloride test (chloride concentration >60 mEq/L is diagnostic). Management: A multidisciplinary approach is required. Regimens include rigorous airway clearance techniques, mucolytics (dornase alfa), inhaled antibiotics (tobramycin for chronic Pseudomonas colonization), pancreatic enzyme replacement therapy (PERT), a high-calorie and high-fat diet, and CFTR modulators (e.g., elexacaftor/tezacaftor/ivacaftor) for eligible genetic mutations.

Comparison Table of Upper Airway Obstruction

Mastering these distinctions is crucial for the SMLE, as rapid clinical decision-making is often tested in emergency vignettes.