Comparative haemodynamic effects of dobutamine and isoproterenol in man

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Abstract
Dobutamine was infused at a rate of 8 mcg/kg/min in 17 patients with or without congestive heart failure. Cardiac output increased from an average 2.92 to 4.45 1/min/m2 (p<0.001) with no change in mean aortic pressure (93.4 to 97.8 mmHg) and only a slight increase in heart rate (78 to 87 beats/min). Left ventricular end-diastolic pressure decreased from an average 19 to 13.7 mmHg (p<0.01). Peak left ventricular dp/dt was doubled (1147 to 2370 mmHg/sec, p<0.001) and Vmax increased from 1.08 to 2.18 circ/sec (p<0.001). In 10 patients given equi-inotropic doses (100 per cent increase in peak dp/dt) Isoproterenol produced a greater increase in cardiac output (71 percent) than Dobutamine (51 percent). isoproterenol caused mean aortic pressure to fall significantly (8 percent) while no change was noted with Dobutamine. Accordingly, peripheral vascular resistances were reduced to a greater extent with Isoproterenol than with Dobutamine (p<0.05). Mean pulmonary arterial pressure decreased significantly (25±5.9 to 22±5.7 mmHg, p<0.05) with Isoproterenol infusion and remained unchanged with Dobutamine infusion. Dobutamine increased both stroke work (57 percent) and minute work (83 percent). With Isoproterenol however, only minute work was significantly increased (90 percent). Dobutamine therefore is a potent inotropic drug, with mild chronotropic and peripheral vascular effects and may be valuable in the management of severe heart failure not associated with hypotension.