Bronchodilators are a group of drugs that function to expand the bronchi and bronchioles' surface in the lungs. Bronchodilators also relax the muscles in the lungs so that the breathing process becomes lighter and smoother. Because of these functions, bronchodilators are often used to treat bronchiolitis in children.

Bronchodilators for Bronchiolitis Treatment
Illustration: A child with bronchiolitis is receiving nebulizer therapy containing bronchodilator drug
Image Source: https://cochranechild.wordpress.com



Bronchodilators (such as salbutamol) are mainly given in the form of an aerosol to relax bronchial smooth muscle and dilate the airway. However, the use of bronchodilators in bronchiolitis cases is not yet supported by clear evidence of its efficacy.

There are three types of bronchodilator drugs that are commonly used, including:
  1. Anticholinergics (tiotropium, ipratropium, glycopyrronium, and aclidinium)
  2. Beta-2 agonists (salmeterol, salbutamol, and formoterol)
  3. Theophylline

Based on the time of action, bronchodilators are divided into two: fast reaction and slow reaction. Rapid reaction bronchodilators are usually given for someone who experiences symptoms of sudden shortness of breath. In contrast, slow reaction bronchodilators are usually aimed at controlling the symptoms of shortness of breath in people with chronic lung disease or asthma.

Bronchiolitis is an acute lower respiratory tract infection caused by a virus, in which 50–90% of cases are caused by the respiratory syncytial virus (RSV). This disease mainly affects children under two years of age and causes inflammation of the lungs' airways, so that the tract fills with debris. Symptoms can include fever, cough, and difficulty breathing as well as wheezing in severe conditions.

The clinical manifestations of bronchiolitis are due to airway filling with infectious debris and are not associated with bronchospasm. Therefore, the efficacy of bronchodilators acting by relaxing bronchial smooth muscle is questionable.



Research studies regarding the efficacy of bronchodilators in treating bronchiolitis

In 2014, the American Academy of Pediatrics (AAP) stated that bronchodilators were no longer recommended to manage bronchiolitis. The results of various scientific studies, both before 2014 and after, support this statement.

In 2014–2017, Dunn et al. conducted an intervention and study on bronchodilators. They attempted to reduce salbutamol use in 3834 bronchiolitis patients in the emergency department (ER) and 1119 hospitalized patients. This intervention succeeded in reducing the use of salbutamol from 43% to 20% in the emergency room and from 18% to 11% in the inpatient room, without increasing admission rates to hospital, duration, and re-visits hospitalization.

A retrospective study on 419 patients in Philadelphia, United States, and a meta-analysis of 977 patients in China, also showed that salbutamol's use had no efficacy in bronchiolitis cases. Salbutamol is not recommended because it causes side effects such as increased pulse rate in infants and an increase in supplemental oxygen demand.

A Cochrane meta-analysis involving 30 studies (1922 infants with bronchiolitis) from various countries also proved the absence of bronchodilators (other than epinephrine) on oxygen saturation, hospitalization rates, length of stay, and disease resolution at home. The use of bronchodilators causes side effects such as tachycardia, oxygen desaturation, and tremors.



Recommended Therapies for Bronchiolitis and Medical Evidence

Since the most causes of bronchiolitis are a viral infection, the disease is self-limiting. Management is generally supportive, such as oxygenation, adequate hydration, optimal nutritional intake, and antipyretic administration if there is a fever. The use of bronchodilators or antivirals is not effective for bronchiolitis, so they are not recommended. Antibiotics are considered if only there are secondary infections by bacteria.

Nebulization of hypertonic saline (3% saline) solutions is used by some clinicians to treat bronchiolitis. However, this practice still has inconclusive medical evidence that it has not been recommended as routine therapy. The use of glucocorticoids is also not recommended in treating bronchiolitis because it has not been proven beneficial.

Use of Epinephrine as a Bronchodilator in treating Bronchiolitis

Although the most commonly used bronchodilator is salbutamol, epinephrine is also sometimes used for bronchodilation. A Cochrane meta-analysis has shown that epinephrine can benefit outpatients by reducing the number of admissions to the hospital within the first 24 hours and improving clinical parameters.

In outpatients, the combination of epinephrine with systemic dexamethasone has also been reported to reduce admission rates. However, the benefits of combining these two drugs are still supported by one study, so it still needs to be studied further.
There is no evidence of a benefit in administering epinephrine to bronchiolitis in hospitalized patients, either with steroids or without steroids.



Summary
The use of bronchodilators (other than epinephrine) in bronchiolitis cases is not recommended because they have not been shown to provide many benefits for patient oxygen saturation, hospitalization rates, length of stay, and resolution disease at home. Epinephrine as a bronchodilator has been reported to be useful for outpatients to reduce admissions to hospital in the first 24 hours and improve clinical parameters, but it is not useful for hospitalized patients.

The use of steroids, either with or without epinephrine, and the use of other therapeutic modalities such as nebulization of hypertonic saline solutions, are still not recommended as routine therapy because they do not have a sufficient evidence base. Management of bronchiolitis is generally only supportive, such as oxygenation, adequate hydration, optimal nutritional intake, and antipyretic administration if there is a fever.