Another respiratory virus season is on us. Respiratory syncytial virus (RSV) hit Baltimore in early November, and our residents are already debating the use of bronchodilators, corticosteroids, and nebulized hypertonic saline to treat infants with bronchiolitis
Their arguments, of course, are fueled by published studies claiming that each of these modalities is beneficial and an equal number demonstrating that they are not. Although there is still no single and definitive therapy for bronchiolitis, we have learned a great deal about this condition in the past 50 years. Unfortunately, much of what we have learned has led to conclusions about what not to do rather than what we can and should do in managing this very common problem.
- Studies from the University of Rochester and elsewhere in the 1970s and 1980s demonstrated that nosocomial transmission of RSV during the winter is not only frequent but that it can be deadly, particularly for infants with underlying cardiac and pulmonary disease. The pediatric community responded by avoiding elective admission of such patients, by testing for RSV in hospitalized infants, and by implementing isolation and infection control practices to prevent transmission from infected to uninfected patients. We now know that bronchiolitis is caused by a variety of respiratory viruses, including rhinovirus, human metapneumovirus, coronavirus, parainfluenza, and probably others; a search for the causative virus in each patient is less important than instituting infection-control practices that will prevent spread of any of them.
- Fifty years ago, respiratory viruses were detected using tissue culture. The process was time consuming and required experienced technologists. Antigen detection techniques followed, using fluorescent antibody (FA) identification in tissue culture, and later to FA and enzyme immunoassay in respiratory secretions, to detect 1 virus at a time.
Polymerase chain reaction (PCR) tests now are available in many laboratories and permit detection of any of 10 or more viruses in a single respiratory specimen in a matter of hours. A recent study from the Netherlands, however, is just one of several such studies demonstrating that identification of a viral pathogen by real time-PCR does not lead to a reduction in hospitalization, shorter hospital stay, or reduced use of antibiotics, even when the results are available in 12 to 36 hours.1
- We've also learned during the past 50 years that using inhaled ribavirin to treat RSV infection is not practical and probably not effective, that monitoring oxygen saturation in infants with bronchiolitis may lead to unnecessary hospitalization, and that waiting until the oxygen saturation in hospitalized infants normalizes delays discharge unnecessarily.
Will today's pediatric residents practice in a time when bronchiolitis can be prevented as effectively as we now prevent measles, or will some future therapy effectively treat its symptoms? Perhaps. But for this winter, at least, we can teach them the things we've learned not to do.
1. Wishaupt JO, Russcher A, Smeets LC, Versteegh FG, Hartwig NG. Clinical impact of rt-PCR for pediatric acute respiratory infections: a controlled clinical trial. Pediatrics. 2011;128(5):e1113-e1120.