Infecciones virales de vías respiratorias inferiores en lactantes hospitalizados: etiología, características clínicas y factores de riesgo

Abstract

Objectives The aim of this study was to assess the clinical and viro-logical characteristics of lower respiratory tract (LRT) infection in hospitalized infants in Spain and to identify clinical, radiological or laboratory parameters that could, on admission, be associated with a more severe clinical course. Patients and methods A prospective study of infants less than 24 months old hospitalized for LRT infection during six consecutive seasons was performed. Results A total of 617 infants were included in the study. Diagnosis was bronchiolitis in 64 %, wheezy bronchitis in 24.6%, laryngitis in 4.4% and pneumonia in 6.8%. The mean age was 269 ± 188 days, the male/female ratio was 1:6 and the mean hospital stay was 6.6 ± 3.5 days. At least one viral agent was identified in 55.6% of the episodes, of which 83.6 % were due to respiratory syncytial virus (RSV). Other less frequently identified viruses were parainfluenza in 7%, adenovirus in 4.3% and influenza in 4%. Coinfection was identified in 6.2 % of RSV-positive infants. These infants were younger (p < 0.005), had higher respiratory distress assessment instrument (RDAI) scores and longer hospital stay than infants in the other etiologic groups. Chest radiographs were performed in 94.3 % of the infants and 39.5 % showed infiltrate or atelectasis. This radiological alteration was significantly associated with a fever of more than 38.5 °C and reactive C protein concentrations of more than 30 mg/L (p < 0.001 and p < 0.002), but not with higher RDAI score, SaO2 equal to or less than 87%, or longer hospital stay. In the crude analysis, hospitalization for more than 5 days was associated with lower age (p < 0.01), a mean RDAI score of more than 6 (p < 0.003), SaO2 equal to or less than 87% (p < 0.01) and RSV infection (p < 0.001). However, in the multivariate analysis only SaO2 equal to or less than 87 % and RSV infection were significantly associated with prolonged hospitalization. Conclusion The most common lower respiratory tract infections in hospitalized infants in Spain are the various types of RSV-positive bronchiolitis, which have a clinical pattern similar to that described in other countries. Hypoxia on admission and RSV infection are the most important risk factors for prolonged hospitalization.