A comparison of cardiovascular effects of dobutamine and isoprenaline after open heart surgery.

In a cross-over study, the cardiovascular effects of dobutamine were assessed in 11 patients who had undergone operation for replacement of the mitral or aortic valve approximately four hours earlier. In 9 of these the effects of isoprenaline were assessed for comparison. Dose-response curves were obtained using four dose levels of dobutamine in the range 1.25-10 mug/kg per min and of isoprenaline in the range of 0.005-0.04 mug/kg per min. Both drugs produced similar dose-dependent increases in heart rate and cardiac output and a dose-dependent decrease in peripheral resistance. Mean arterial pressure was only slightly increased by either drug. The positive inotropic effect of dobutamine was confirmed, but the chronotropic effect was not significantly different from that of isoprenaline. This contrasts with the findings of previous studies, and possible reasons for this are discussed.