Hemodynamic effects of an inhaled beta-2 agonist

We examined echocardiographically in a single-blind crossover trial the circulatory effects of an inhaled selective beta 2-adrenergic bronchodilator, fenoterol. Eight healthy subjects were studied on the first and fourteenth day after randomly assigned therapy with either no drug or 400 micrograms fenoterol by metered dose inhaler four times a day. Heart rate (HR) and systolic (SBP) and diastolic (DBP) blood pressure responses to fenoterol were small (means +/- SE; HR: +4 +/- 1.3 bpm; SBP: +6 +/- 1.3 mm Hg; DBP: -3 +/- 1.4 mm Hg). In contrast, mean cardiac output increased 26% (1.1 +/- 0.2 l/min), accompanied by an 18% fall in total peripheral vascular resistance (-6 +/- 1.3 U), a 16% increase in stroke volume (+12 +/- 2.5 ml), and an 18% increase in the mean velocity of circumferential shortening (+0.2 +/- 0.04 c/s). Responses varied widely among subjects; maximum observed increase in cardiac output was 117% (+5.48 l/min) in one subject. There was no evidence to suggest development of tolerance to these hemodynamic effects, as the response of measured variables did not differ after 2 wk of regular fenoterol therapy. We conclude that selective beta 2-bronchodilators are not without potential for hemodynamically significant effects when taken by metered inhalers in recommended therapeutic doses and that the magnitude of such effects is underestimated when measured by HR and blood pressure changes.