Clinical and epidemiological study of acute bronchiolitis in patients less than one year of age

Objective. To analyze the epidemiological, etiological, clinical and laboratory features of acute bronchiolitis in infants less than 12 months of age. Material and Methods. Infants with bronchiolitis that had been diagnosed in our Hospital Emergency Room between December 1st, 2001, and January 31st, 2002, were studied retrospectively. We obtained epidemiological data (age, sex, risk factors), etiological features (virological study of nasopharyngeal secretions including immunofluorescence, immunochromatography and culture), clinical characteristics (presentation and complications) and blood tests (differential cell count, biochemistry and acid-base balance). Results. Two hundred twenty-nine patients with bronchiolitis (59% male) were studied. Seventy-five percent of the patients were discharged after emergency room evaluation; the remaining 25% required hospital admission with 8% admitted to the pediatric intensive care unit (PICU). Seven patients required mechanical ventilation. Infants between 4 and 8 months are those most frequently affected, but children of less than 4 months of age were hospitalized more often. Respiratory syncytial virus (RSV) was identified in 67% of the children. Influenza virus was isolated in 15% of those aged between 8 and 12 months. Apneas, tachycardia, cyanosis, acidosis and high C-reactive protein levels were more common among patients that required the PICU. Two patients with risk factors had severe complications: one presented congestive heart failure and the other died of multiple organ failure. Conclusions. Viruses other than RSV, particularly influenza virus, are isolated in acute bronchiolitis. Although it is usually mild, acute bronchiolitis can be a severe disease in patients with risk factors.