Most studies of inhaled beta2-agonists were done in Accident and Emergency departments and involved monitoring people over 1–6 hours; the findings are therefore difficult to generalize to primary care. However, continuous beta2-agonist treatment or the addition of ipratropium bromide appears to reduce the number of people hospitalized with a severe asthma exacerbation:
- Beta2-agonist dose and frequency:
- A randomized controlled trial (RCT, n = 100) in adults with acute asthma showed that six sprays of salbutamol via a metered-dose inhaler every 60 minutes was safe and effective, but some people who did not respond initially may benefit from treatment 30 minutes after the first inhalation. Treatment intervals of 60 minutes (compared with 30 minutes or 120 minutes) seemed to provide optimal results in most people, and hospitalization rates and adverse events did not differ [Karpel et al, 1997].
- Beta2-agonists via a pressurized metered-dosed inhaler versus a nebulizer:
- A systematic review (six RCTs, n = 491 children < 5 years of age) showed a metered-dose inhaler with a spacer to be more effective than a nebulizer. The children who received nebulizers had higher admission rates [Castro-Rodriguez and Rodrigo, 2004]. Children are less likely to have tachycardia and hypoxia when using a pressurized metered-dose inhaler with spacer compared with a nebulizer [SIGN and BTS, 2011].
- Continuous versus intermittent beta2-agonists:
- One systematic review (search date 2004, eight RCTs, n = 461) found that continuous nebulized beta2-agonists significantly reduce hospital admission compared with intermittent nebulized beta2-agonists, especially in people with severe airflow obstruction (RR 0.64, 95% CI 0.50 to 0.90). Adverse effects, such as heart rate and blood pressure elevation and tremor, did not differ between groups [Rodolfo et al, 2005].
- Ipratropium bromide added to beta2-agonists:
- Two systematic reviews and one subsequent RCT found that the addition of ipratropium bromide to beta2-agonists in acute severe asthma improves lung function and is likely to reduce hospital admission [Rodolfo et al, 2005].