Bronchiolitis, usually seen in children younger than two years, manifests as rhinorrhea, cough, expiratory wheezing, and respiratory distress. After several days, cough worsens and there is evidence of lower respiratory tract involvement including difficulty breathing and intercostal retractions. Bronchiolar narrowing is exacerbated by the positive expiratory pressure when the child tries to forcefully exhale to overcome narrowed passageways. Symptoms usually begin eight to 12 days after infection secondary to inflammation, even though viral load peaks in four to five days. The differential diagnosis includes infantile asthma, in which infants present with recurrent cough, wheezing, and tachypnea. Panitch reviews the supportive care and therapies designed to overcome airway obstruction in patients with respiratory syncytial virus bronchiolitis.
Although the foundation of management of respiratory syncytial virus disease is supportive care with fluid replacement and supplemental oxygen, treatments to dilate constricted bronchi can be useful. These treatments include corticosteroids, bronchodilators, helium/oxygen therapy, and exogenous surfactant, which are used to decrease disease duration and improve morbidity and mortality.
Supportive treatment with parenteral fluids is often required to maintain hydration but must be administered carefully because of the risk of pulmonary congestion. Hospitalized infants should be given humidified, supplemental oxygen when they are hypoxemic, and pulse oximetry monitoring is recommended. Mechanical ventilation may be needed in severe cases in children who develop apnea or respiratory failure. Saline drops and suction can help keep the nasal passages clear. Airway obstruction is caused by plugs formed from mucus and desquamated epithelial cells. Enhanced smooth muscle tone increases bronchospasm. Beta-adrenergic agonists may be useful when bronchospasms are present, and anti-inflammatory therapy may be useful when an inflammatory process dominates the clinical picture.
No clear evidence supports the use of chest physiotherapy, inhaled corticosteroids, mucolytic agents, or theophylline in the management of bronchiolitis. Beta2 agonists are helpful in asthma, but bronchospasm is not a major characteristic of bronchiolitis. Combinations of alpha and beta agonists may be more helpful because of the resultant decrease in airway mucosal edema, but benefits have not been consistent. Theophylline does not affect the clinical course of bronchiolitis, but theoretic benefits include increased responsiveness to carbon dioxide, stimulation of respiration, and increased diaphragmatic contractility. Use of systemic corticosteroids appears to reduce the duration of symptoms, especially if given early and if used in infants with more severe symptoms. Recent studies also show decreased hospitalization if systemic steroids are used early in infants with mild to moderate cases of bronchiolitis. Inhaled epinephrine or anticholinergics have not demonstrated consistent clinical benefit. Combination therapy with systemic cortico-steroids and inhaled beta agonists has shown some promise. Further studies are needed to examine the ability of exogenous surfactant to prevent small airway obstruction. Helium/oxygen therapy can decrease airway resistance, providing symptom relief and time for the disease to resolve naturally.
The author concludes that treatments beyond supportive care in children with bronchiolitis should be individualized. Further studies are needed to make specific universal recommendations about treatments beyond hydration and oxygen maintenance.
In the same journal issue, Jafri reviewed antiviral therapies with ribavirin respiratory syncytial virus immunoglobulin intravenous (RSV-IGIV), and palivizumab, an IgG mono-clonal antibody for bronchiolitis. Aerosolized ribavirin may be useful early when the viral load is maximal (four to five days after infection). RSV-IGIV may decrease disease severity, but more studies are needed. Palivizumab inhibits viral fusion to the epithelial cells and is approved for prophylaxis in high-risk infants. The use of palivizumab during acute disease has not shown clear significant benefit.