Haemodynamic responses to salbutamol and isometric exercise are altered in young adults with mild asthma.

OBJECTIVES

Tolerance to the haemodynamic effects of regularly inhaled beta(2) agonists has been reported in a research setting. It is unclear whether cardiovascular responses in adults with asthma are influenced by their use in routine clinical practice. This study aimed to characterise the effects of acute salbutamol administration on systemic haemodynamics in adults with mild asthma who were receiving intermittent beta(2) agonist treatment.

METHODS

Ten patients with mild asthma and ten healthy age and sex-matched controls were recruited to a randomised placebo-controlled double-blind two-way crossover study. Each received salbutamol 200 mug or placebo, then performed sustained isometric handgrip exercise as an adrenergic cardiovascular stimulus. Heart rate and blood pressure responses were observed during rest and exercise, and cardiac index and systemic vascular resistance index were measured using non-invasive impedance cardiography.

RESULTS

Isometric exercise caused a greater increase in heart rate (12+/-3 vs. 8+/-3 bpm, P<0.01) and diastolic blood pressure (19+/-3 vs. 12+/-3 mmHg, P<0.01) in patients with asthma compared with healthy controls. Salbutamol administration significantly increased heart rate, blood pressure and cardiac index in healthy controls, but these responses were attenuated in patients with asthma.

CONCLUSION

These findings indicate that adults with asthma, who are receiving intermittent beta(2) agonist treatment, have a greater cardiovascular responses to sympathetic stimulation, and haemodynamic tolerance to acute salbutamol administration.