Bronchiolitis

Bronchiolitis is characterized by inflammation and edema of the lower airways due to infection and generally affects children <2 years of age. Signs and symptoms include cough, fever, rhinorrhea, increased work of breathing, hypoxemia, and in severe cases, respiratory failure. Viral bronchiolitis is one of the most common causes of pediatric hospitalization annually, resulting in 57,000 to 172,000 hospitalizations at a cost of $1.7 billion each year. Historically, the acute management of bronchiolitis was somewhat heterogeneous, but in 2014, pediatric providers agreed on standard practices for diagnosis, management, and prevention of bronchiolitis in the American Academy of Pediatrics (AAP) Clinical Practice Guideline.

Assessment

Respiratory syncytial virus (RSV) is the leading cause of viral bronchiolitis in young children. RSV is detected in the nasopharyngeal secretions of up to 80% of children diagnosed with bronchiolitis. Patients with suspected bronchiolitis who require prolonged ED observation or admission should undergo RSV polymerase chain reaction (PCR) testing for rapid decision about whether admission is required.

(Source: Viral Bronchiolitis in Children. N Engl J Med 2016.)

Pathogenesis

The pathogenesis of RSV involves increased mucus production and sloughing of the pulmonary epithelium in the lower airways, leading to obstruction of the small airways, producing coarse wheeze and rales on auscultation. Because the exam is quite fluid and variable over time, serial examination is informative. In most cases, chest imaging and screening blood work are not recommended, as bronchiolitis is principally a clinical diagnosis. The decision to admit a patient for bronchiolitis is multifactorial, but important considerations include the presence of hypoxemia, increased work of breathing, and dehydration or feeding intolerance.

(Source: Viral Bronchiolitis in Children. N Engl J Med 2016.)

Management

The mainstay of bronchiolitis management is supportive care as outlined in the 2014 AAP bronchiolitis guidelines. Routine ordering of chest radiographs and the use of bronchodilators or systemic glucocorticoids for uncomplicated bronchiolitis are not recommended. Antibiotics are generally not warranted because the etiology of most pediatric bronchiolitis episodes is viral.

(Source: Viral Bronchiolitis in Children. N Engl J Med 2016.)

Recurrent wheezing: After an initial presentation with bronchiolitis or RSV-associated wheezing, some children will continue to have episodes of recurrent wheezing with subsequent viral illnesses. In such cases, careful review of the patient’s history for environmental and seasonal triggers associated with wheeze, atopy, and family history of wheeze is important. A subset of children might benefit from asthma medications (e.g., short-acting bronchodilators, inhaled glucocorticoids, or leukotriene receptor antagonists).

(Source: The Challenge of Managing Wheezing in Infants. N Engl J Med 2009.)

RSV Prophylaxis: Infants and children at high risk for severe pulmonary sequelae of RSV infection, specifically those with a history of prematurity, chronic lung disease, and certain types of congenital heart disease, may benefit from seasonal prophylaxis with an anti-RSV monoclonal antibody.

• Nirsevimab is a long-acting anti-RSV monoclonal antibody that targets the perfusion F protein on the surface of RSV and was approved by the FDA in 2023. Because of its long half-life, a single injection can provide passive immunity for the entire RSV season.

  • Nirsevimab is approved for administration to all infants younger than 8 months who are entering their first RSV season and whose mother did not receive RSV vaccination during pregnancy.

    • Infants born during the RSV season should receive nirsevimab within one week of birth.

  • Nirsevimab is also approved for high-risk children older than 8 months entering their first RSV season and high-risk children aged 8 to 19 months entering their second RSV season.

    • High-risk conditions include prematurity, impaired mucociliary clearance, neuromuscular disorders that impair airway clearance, immune suppression or deficiency, congenital heart disease, other forms of chronic lung disease, and any other condition that increases risk for severe RSV disease.

  • Nirsevimab is estimated to have approximately 80% efficacy in preventing RSV-associated lower respiratory tract infections and RSV-associated hospitalizations.

• Palivizumab is another anti-RSV monoclonal antibody that remains available for high-risk populations but is only recommended if nirsevimab is not available. In a placebo-controlled study involving preterm infants (gestational age, 33-35 weeks), the administration of palivizumab for RSV prevention reduced the total number of cumulative days with wheezing in the first year of life. The effects of nirsevimab on wheezing within the first year of life have not been studied.

(Source: Viral Bronchiolitis in Children. N Engl J Med 2016.)

(Source: Respiratory Syncytial Virus and Recurrent Wheeze in Healthy Preterm Infants. N Engl J Med 2013.)