Haemodynamic effects of terbutaline in chronic obstructive airways disease

Terbutaline, a cardioselective beta-adrenoceptor agonist, administered intravenously (250 micrograms) to seven patients with chronic obstructive airways disease (mean FEV1 0.99 l) resulted in reduction of mean pulmonary artery pressure (resting 23 +/- 2 to 19 +/- 2 mmHg, p < 0.05; exercise 43 +/- 3 to 35 +/- 3 mmHg, p < 0.05) and calculated pulmonary vascular resistance (resting 168 +/- 27 to 109 +/- 17 dyne s cm-5, p < 0.01; exercise 170 +/- 30 to 119 +/- 18 dyne s cm-5, p < 0.01) accompanied by an increase in heart rate (resting 86 +/- 5 to 96 +/- 4 per min, p < 0.01; exercise 108 +/- 2 to 114 +/- 2 per min, p < 0.01) and cardiac output (resting 3.7 +/- 0.4 to 4.1 +/- 0.4, p < 0.05; exercise 4.9 +/- 0.06 to 6.1 +/- 6 l, min-1 m-2, p < 0.05). The haemodynamic changes were associated with an increase in resting peak expiratory flow rate (184 +/- 20 to 216 +/- 25 l/min, p < 0.01), while the calculated indices of ventilation/perfusion relationship remained essentially unchanged. The reduction in mean pulmonary artery pressure after terbutaline observed in the present studies was probably the result of a combination of simple vasodilator effect, the reduction in airways resistance, and increase in the ventilation.