Nebulized hypertonic saline is an emerging therapy for this indication.
Viral bronchiolitis is the most common diagnosis at hospitalization for infants who are younger than 1 year of age.
It results in approximately 150,000 hospitalizations each year at a cost of more than $500 million, according to a study published in 2006 (Pediatrics 2006;118:2418-23). Yet so far, nothing we give our patients really works.
Nebulized hypertonic saline is garnering enthusiasm because there is a consistent set of papers and a theory of physiology supporting its efficacy in the treatment of acute viral bronchiolitis.
The very first hypertonic saline study came from a group of Israeli pulmonologists who reported an improvement in symptoms and respiratory scores on day 2 of inhaled nebulized 3% saline solution plus 5 mg terbutaline in 33 outpatient infants with viral bronchiolitis, compared with 32 control infants who received 0.9% saline plus 5 mg terbutaline (Chest 2002;122:2015-20).
The findings led the researchers to conduct a second randomized, controlled study, this time combining 3% hypertonic saline with 1.5 mg epinephrine three times a day until discharge among 27 hospitalized infants. Clinical severity scores improved significantly after 24 hours of therapy and almost a full day was shaved off the length of stay (LOS), compared with normal saline plus epinephrine in 25 infants (Chest 2003;123:481-7).
The group came back a year later with a second year of follow-up in 41 inpatients and essentially replicated their findings (Isr. Med. Assoc. J. 2006;8:169-73).
The study that caught most physicians’ eyes, however, was a multicenter, double-blind Canadian trial that left the concomitant use of beta-agonists up to the discretion of the physicians who treated 96 infants hospitalized with moderately severe viral bronchiolitis (J. Pediatr. 2007;151:266-70). Even though 30% of the infants did not receive beta-agonists, the use of hypertonic saline resulted in a clinically relevant 26% reduction in LOS (from 3.5 days to 2.6 days), compared with normal saline. Symptoms diverged the longer the infants were treated.
Short-term improvement was not really expected, based on the theory that hypertonic saline works by rehydrating the airway surface liquid (ASL), as well as inducing cough and improving sputum mobility. The Israelis theorized that mucociliary failure, such as occurs in cystic fibrosis, also occurs in severe bronchiolitis because of dehydration of the ASL, the thin layer of fluid that covers the luminal surface of the airway.
In vitro, hypertonic saline increases airway surface thickness, decreases epithelial edema, and improves mucus rheology and transport rates. In vivo, it increases mucociliary transport in healthy subjects.