Efficacy and Safety of Increasing Doses of Inhaled Albuterol in Children With Acute Wheezing Episodes

Metered dose inhalers with spacers are devices capable of providing higher rates of lung deposition of drugs such as beta agonists when compared to conventional nebulizers, but there is no consensus about the optimal dose when this is the device of choice and there is evidence that younger children need proportionally higher doses of albuterol (in μg/kg) when compared to older children. Other factors that may interfere with response to albuterol treatment include the genetics of the beta adrenergic receptor (ADRβ2) and infectious etiology of the wheezing attack. This study will assess the effectiveness of a dose regimen that prioritizes higher doses of albuterol, with doses in μg/kg higher for younger children. Security of this new dosing regimen will be assessed by monitoring clinical side effects and serum levels of albuterol, but the investigators will also examine the presence of 12 different respiratory viruses in these patients and evaluate the influence of ADRβ2 receptor genetics in the response to albuterol. The primary outcome measure will be the need for hospitalization. Secondary outcomes will include a change in clinical score, respiratory rate and forced expiratory volume in the first second, the need for additional treatments and length of stay in the emergency room for those not hospitalized.

This is a prospective, randomized, double blinded, controlled study. The patients will be randomly assigned to one of the treatment groups (experimental or control groups).

The patients will be assessed 1 hour later and every 30 minutes thereafter until discharge. Following 4 hours in the emergency room, any patient who do not meet the discharge criteria (PRAM score ≤ 3 and SpO2 ≥ 92%) will be admitted to the hospital. Each patient's attending physician will determine the need for additional therapies following the first hour.

Identification of respiratory viruses in the nasal lavage samples wil be performed using the CLART PneumoVir® kit.

Albuterol plasmatic levels will be analyzed via HPLC (High Performance Liquid Chromatography).

To genotype the ADBR2 receptor (blood samples), the gene regions encompassing the Arg16Gly, Gln27Glu, and Arg19Cys Thr164Ile polymorphisms will be amplified via PCR. The resultant amplimers were then sequenced.

A sample of 124 patients (62 in each group) was calculated to provide an 80% power with which to detect a significant difference of at least 30 minutes in the lengths of stay between the groups. The chi-square test will be used to compare hospital admission rates and tremor rates. For all other outcomes, t-tests for mean comparisons (variables with a normal distribution), a Mann Whitney test (nonparametric data) and ANOVA with repeated measures will be used.

Eligibility Criteria:
Inclusion Criteria:

1. Aged 2 to 18 years;
2. History of two or more previous episodes of wheezing treated with bronchodilators in the last year;
3. Wheezing attacks characterized by coughing, difficulty breathing and auscultation of expiratory wheezing or prolonged expiration;
4. Intensity of wheezing attacks defined by PRAM score as moderate or severe (PRAM ≥ 5).

Exclusion Criteria:

1. Pre-existing chronic diseases such as bronchopulmonary dysplasia, cystic fibrosis, bronchiolitis obliterans or other chronic pulmonary or cardiovascular disease;
2. Initial clinical status indicating immediate ventilatory support, need for subcutaneous or intravenous bronchodilators;
3. Decreased level of consciousness;
4. Using a β-agonist in the four hours prior to arrival.
5. Use of corticosteroids in the last 24h.