Case of the Month #29 Bronchiolitis

Bronchiolitis is an acute viral infection of the lower respiratory tract.  It is the leading cause of hospital admission in infants under 1 year of age[1]. By age 3 virtually all children have serological evidence of RSV infection but only a minority will develop bronchiolitis2. The most common cause is Respiratory Syncytial virus (RSV). The RSV “season” in the Northern hemisphere extends from November to March with peak incidence occurring in January or February. Rhinovirus (RV) is the next most common cause with peaks in spring and autumn. Other viruses, besides RV & RSV, including human metapneumovirus, influenza, parainfluenza, enterovirus, and adenovirus can cause bronchiolitis, as well.

Bronchiolitis caused by RSV and other respiratory viruses begins as an upper respiratory tract infection, with coryzal symptoms such as rhinitis and cough, which then spreads to the lower respiratory tract in 1 to 3 days. The diagnosis is clinical with cough, wheeze, and laboured breathing. Physical examination usually reveals tachypnoea, fever, retractions, wheezes, crackles, and sometimes thoracoabdominal asynchrony. Not all infants present with wheezes or crackles. In young infants, particularly if born preterm, episodes of apnoea may be the first presentation of bronchiolitis.

The infant with typical acute bronchiolitis requires no specific investigation. However, in hospital, rapid virological testing for RSV by nasopharyngeal aspirate and/or polymerase chain reaction (PCR) can aid in diagnosing RSV bronchiolitis. Additionally, because there are no pathognomonic signs on chest x-ray it should be performed only if there is a strong suspicion for bacterial pneumonia. An oxygen saturation target of 92% or higher is considered as safe and clinically effective as one of 94% or higher.

Although most infants with bronchiolitis present a mild clinical form and can be safely managed at home, some, especially those who are very young and/or have significant comorbidities will need a hospital admission (see below). Jacob’s current clinical condition warrants a hospital admission.

On day 3, Jacob’s hypoxemia worsened, respiratory rate increased, and he was unable to feed due to increasing lethargy from his increased work of breathing. CXR showed a right lobar pneumonia, suggestive of a secondary bacterial infection.