Viral bronchiolitis (Part three)
Viral bronchiolitis: Prognosis, Preventative treatments.
A significant number of patients who are hospitalized for bronchiolitis subsequently have recurrent episodes of wheeze and may develop asthma later in life. There is some evidence that infants who develop RSV bronchiolitis have reduced lung function before becoming infected with RSV and that there is a genetic predisposition to post-bronchiolitis wheeze. Debate continues around the exact mechanism of the post-bronchiolitis wheeze and whether RSV may be a cause or a consequence of airway pathology. It is apparent from cohort studies that if there's no case history of atopy, the wheezing tendency post-bronchiolitis will resolve by 10 years aged.
Prevention of post-bronchiolitis wheeze
Despite many studies looking to stop the post-bronchiolitis wheeze seen after RSV bronchiolitis, no treatment has been shown to be effective. Steroids, used during the acute phase, have been studied most widely in this context without revealing consistently successful results. A systematic review of the use of steroids to prevent post-bronchiolitis wheeze has shown no effect and currently, there is no evidence to support the use of steroids in bronchiolitis to prevent post-bronchiolitis wheeze. Ribavirin has also been studied without success.
As mentioned above, a variety of treatment regimens are employed to scale back infection with RSV bronchiolitis.
RSV Ig and palivizumab
Both RSV Ig and palivizumab are shown to scale back RSV bronchiolitis admissions. Although both RSV Ig and palivizumab are licensed for use in the prevention of RSV bronchiolitis, only palivizumab can be used in infants with hemodynamically significant congenital heart disease. If RSV Ig is employed, it must be remembered that it's going to inactivate live vaccines (such as measles-mumps-rubella) and these may have to be repeated nine months after the administration of RSV Ig. Both RSV Ig and palivizumab are expensive to administer (RSV Ig is given monthly by injection for five months, and palivizumab is given monthly by injection for five months - starting October to December), but palivizumab has been shown to be more cost-effective and is generally favored as the prophylactic agent of choice. Palivizumab was seen in a large multicentre randomized controlled trial to reduce hospital admissions by 55% when used prophylactically in high-risk infants (preterm less than 32 weeks gestation) although there was no difference in mortality. The expense of introducing routine prophylaxis with palivizumab is considered prohibitive and several studies have examined the feasibility of such an approach. The consensus seems to be that palivizumab prophylaxis should not be routinely administered to all preterm infants but be reserved for those most at risk. A cost-effectiveness study showed that preterm infants with bronchopulmonary dysplasia who were discharged home from the neonatal intensive care unit between September and December and required home oxygen were those most likely to benefit. The American Academy of Pediatrics has published revised guidance on the use of palivizumab for the prevention of RSV infection to only cover preterm infants who have at least two other risk factors rather than routine administration to all preterm infants.
Handwashing and limiting contact
There are no systematic reviews (or) randomized controlled trials on these measures, but observational studies have shown that cohort nursing, handwashing, and eye-nose goggles all reduce nosocomial infection when used alone. Guidance from the Centers for Disease Control and Prevention suggests frequent handwashing and not sharing items such as cups, glasses, and utensils with persons who have RSV illness should reduce the risk of spread. It is not thought necessary to exclude children with colds or other respiratory illnesses (without fever), who are well enough to attend daycare or school settings. In the hospital setting, general consensus is that there should be strict adherence to handwashing, and gowns and gloves should be worn. It is also advisable to limit the number of patient contacts and visitors during epidemics.
There is strong evidence that smoking increases the danger of admission with bronchiolitis and this appears to be a postnatal exposure instead of antenatal. It would follow that ensuring parents didn't smoke within the same room as their infants would be wise advice to scale back RSV bronchiolitis. Vaccination development of an RSV vaccine is a high research priority. The problems are that the vaccine would have to induce immunity that is more durable than that seen after natural infection, and it would have to be given at a very young age when maternal antibodies are present (neonates receive high titers of maternally acquired anti-RSV antibody which explains why infection is rare within the first 4 weeks of life). The first vaccine produced was an inactivated vaccine that produced high levels of serum antibody but resulted in a more severe course of disease following infection by the wild virus. Currently, trials are being administered on various vaccines including vaccines that focus on the fusion (F) and attachment (G) transmembrane glycoproteins of the RSV virus.