Bronchiolitis is an acute wheezing-associated illness, which preceeds by signs and symptoms of an upper respiratory infection. Infants may have a single episode or may have multiple occurrences in the first year of life.
Bronchiolitis is most serious in infants who are less than one year old, especially those 1-3 months old.
Bronchiolitis occurs most frequently from early November and continues through April.
The leading cause of bronchiolitis in infants and young children is the respiratory syncytial virus (RSV),accounting for 50% of cases of bronchiolitis requiring hospitalization.
Infants born prematurely, or with chronic lung disease (CLD), immunodeficiency or congenital heart disease are at especially high risk for severe RSV illness.
RSV is transmitted by contact with nasal secretions. Symptoms usually last an average of 5 days.
Parainfluenza viruses are the second most frequent cause of bronchiolitis. They cause illness during autumn and spring, before and after outbreaks of RSV.
Influenza A virus,adenovirus, rhinovirus and Mycoplasma pneumonia can all cause bronchiolitis.
Rhinovirus and mycoplasma pneumonia cause wheezing-associated respiratory illness in older children, while para influenza virus and RSV can cause wheezing at any age.
3. Clinical evaluation of bronchiolitis
Symptoms of RSV may range from those of a mild cold to severe bronchiolitis or pneumonia. RSV infection frequently begins with nasal discharge, pharyngitis, and cough. Hoarseness or laryngitis is not common. Fever occurs in most young children, with temperatures ranging from 38°/C to 40°/C (100.4°/F to 104°/F).
Hyper resonance of the chest wall may be present, and wheezing can be heard in most infants. The wheezing sound is harsh and low in pitch, although severely affected infants may not have detectable wheezing.
Cyanosis of the oral mucosa and nail beds may occur in severely ill infants.Restlessness and hyperinflation of the chest wall are signs of impending respiratory failure.
Infants with bronchiolitis present symptoms of an upper respiratory illness for several days and wheezing during the peak RSV season.
Chest radiography typically shows hyper expansion and diffuse interstitial pneumonitis.
Oxygen saturation values of lessthan 95% suggest the need for hospitalization.
Arterial blood gases should be obtained to assess the severity of respiratory compromise. Carbon dioxide levels are commonly in the 30-35 mm Hg range. Respiratory failure is suggested by carbon-di-oxide values of 45-55 mm Hg. Oxygen tension below 66 mm Hg indicates severe disease.
White blood cell count may be normal or elevated slightly, and the differential count may show neutrophilia.
Enzyme-linked immunosorbent assays (ELISA) of nasal washings for RSV are highly sensitive and specific.
Criteria for hospitalization
- History of prematurity (especially less than 34 weeks)
- Congenital heart disease
- Other underlying lung disease
- Low initial oxygen saturation suggestive of respiratory failure
- Age lessthan 3 months
- Dehydrated infant who is not feeding well
- Unreliable parents
Hospitalized infants should receive hydration and ambient oxygen to maintain an oxygen saturation >92-93% by pulse oximetry.
Treatment of bronchiolitis
Racemic epinephrine by inhalation may be administered as a therapeutic trial. It is given every 20-30 minutes for severe croup, and it is given every 4-6 hours for moderate croup.
Ribavirin, an antiviral agent, produces modest improvement in clinical illness and oxygenation. Ribavirin is helpful in severely ill or high-risk patients.
Treatment with ribavirin combined with RSV immune globulin administered either parenterally or by aerosol is more effective than therapy with either agent alone. Corticosteroid use in the treatment of bronchiolitis is not recommended.
6. Prevention of RSV Infections
Palivizumab (Synagis) is a humanized mouse monoclonal antibody that is given intramuscularly.
Palivizumab is administered intra muscularly in a dose of 15 mg/kg once a month during the RSV season.