MONTEVIDEO, URUGUAY—The prognosis for patients with rapid-onset asthma attacks may be markedly different from the prognosis for those patients with slow-onset attacks. A new prospective study reveals that patients with rapid-onset attacks have a faster response to treatment and a lower risk of hospital admission than do patients with slow-onset attacks.[1]

“Rapid-onset asthma attacks constitute a distinct but uncommon acute asthma emergency department presentation,” said lead study author Gustavo J. Rodrigo, MD, in an interview with RESPIRATORY REVIEWS. “These patients have a rapid deterioration followed by a more rapid response to treatment and a lower [hospital] admission rate than do slow-onset asthma attack patients.” Dr. Rodrigo and his colleague conducted a prospective cohort study to assess the relative frequency of rapid-onset and slow-onset attacks in adult patients with severe asthma who presented to an emergency department. They also investigated whether these two groups of patients differed in terms of clinical and spirometric characteristics or response to treatment.

Subjects included 403 patients (ages 18 to 40 years) with acute exacerbations of asthma and peak expiratory flow (PEF) and forced expiratory volume in one second (FEV1) of less than 50% of predicted value. Only 41 patients (11.3%) met the criterion for rapid-onset attacks (onset less than six hours). All patients were treated with albuterol, four puffs every 10 minutes for three hours (100 µg per actuation).

With the exception of gender, patient characteristics did not differ between the two groups. Men made up slightly more than half of the patients with rapid-onset attacks but only about a third of those with slow-onset attacks. The most commonly reported trigger for slow-onset attacks was acute respiratory tract infection. In contrast, patients with rapid-onset attacks were more likely to have an unidentifiable trigger. In addition, they were more likely to have lower pulmonary function measurements at initial presentation (FEV1, 0.7 L vs 0.9 L in the patients with slow-onset attacks). None of the other clinical factors measured, including sensitivity to specific aeroallergens or ingested substances and environmental factors, appeared to increase patients’ risk of rapid-onset asthma attacks.

Both groups experienced significant improvements in mean PEF and FEV1 following their treatment. However, patients with rapid-onset attacks experienced greater overall improvements in these variables than did patients with slow-onset attacks. Further, the differences in treatment results increased over time. Also, posttreatment arterial oxygen saturation levels were higher and accessory muscle use was lower in patients with rapid-onset attacks.

“Because rapid-onset asthma attack patients have a rapid response to treatment, they should immediately be given high doses of ß-agonists, anticholinergics, and oxygen. Objective measurement of pulmonary function should be obtained to monitor response to treatment as soon as possible,” noted Dr. Rodrigo, a physician in the emergency department at Hospital Central de las Fuerzas Armadas in Montevideo, Uruguay.

Not surprisingly, patients who have slow-onset asthma attacks had a higher risk of hospital admission than did patients with rapid-onset asthma attacks.

--Deborah L. O’Connor