Therapeutic response patterns to high and cumulative doses of salbutamol in acute severe asthma.
OBJECTIVE
To examine the main therapeutic response patterns to high doses of salbutamol and to determine the factors that contribute to outcome in acute severe asthma.


METHODS
The emergency department (ED) of a large, urban hospital with primary and referral care responsibilities.


METHODS
One hundred sixteen consecutive patients with acute exacerbations of asthma were enrolled in the trial, using a prospective sequential design.


METHODS
All patients were treated with salbutamol delivered with a metered-dose inhaler into a spacer device in four puffs (400 microg) at 10-min intervals. The protocol involved 3 h of this treatment (1,200 microg each 30 min).


RESULTS
A dose-response increase in pulmonary function was found, but only 70% improved sufficiently to be discharged. Of these, almost 70% required < or =2.4 mg of the drug within 1 h to reach the discharge threshold, whereas the remainder 30% need > or =3.6 mg. In 30% of subjects, salbutamol was ineffective. These patients were characterized by a more severe disease as judged by previous beta2-agonist use, larger duration of attack before ED visit, and a more severe obstruction at presentation. However, the most important predictors of outcome were peak expiratory flow rate (PEFR) as percent of predicted, PEFR as liters per minute, and PEFR variation over baseline value, all at 30 min.


CONCLUSIONS
This study described two different therapeutic response patterns to salbutamol. Almost 70% of patients were sensitive to salbutamol (good response pattern), and in this group, 2.4 to 3.6 mg represents optimal treatment. In the remainder 30% of patients (poor response pattern), salbutamol in high doses had little effect. However, the outcome was not determined by the intensity of the initial symptoms or by the value of the presenting PEFR, but rather by the early (30 min) short-term response to treatment.
Rodrigo
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Centro de Tratamiento Intensivo, Asociación Española Primera de Socorros Mutuos, Montevideo, Uruguay. gurodrig@varela.reu.edu.uy
Rodrigo
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D000208:Acute Disease; D000280:Administration, Inhalation; D000293:Adolescent; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage*; D000328:Adult; D000420:Albuterol / Q000008:administration & dosage*; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004638:Emergency Treatment; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000187:drug effects; D011446:Prospective Studies
D000318:Adrenergic beta-Agonists; D001993:Bronchodilator Agents; D000420:Albuterol