Both dopamine, a naturally occurring catecholamine, and dobutamine, a synthetic catecholamine, have powerful positively inotropic, mild chronotropic, arrhythmogenic, and vascular effects. Dopamine raises arterial pressure by its a-adrenergic effect, but both catecholamines augment myocardial contractility by stimulation of (3-adrenergic receptors. Dobutamine is unique in that it has two stereoisomers: the (-)-isomer is more potent than the (H-)-isomer for the a-adrenergic receptor sites, while the reverse was found for the p-adrenergic receptors; moreover, the (-h)-isomer has some competitive a-adrenergic receptor blocking properties. In dogs, dobutamine increases coronary blood flow and myocardial oxygen delivery equal to, or in excess of, the increased oxygen required for positive inotropy. Most of the clinical literature on the effects of dobutamine have been concerned with cardiac patients with low cardiac output. http://cheap-asthma-inhalers.com/
Dopamine is often used in hypotensive postoperative states to improve blood pressure and hemodynamics, while dobutamine is often used for short-term positively inotropic therapy for reduced myocardial contractility from chronic low-output congestive failure, chronic coronary insufficiency, myocardial infarction with or without cardiac failure, nonobstructed coronary arterial disease, congestive my-ocardiopathy, cardiogenic shock, and septic sfyock; however, there were differing reports on the effects of dobutamine during the intraoperative and postoperative period after cardiac surgery. Steen et al noted only subtle differences in the effects of dobutamine, dopamine, and epinephrine in patients emerging from cardiopulmonary bypass surgery; however, studies by Gray et al and by Sakamoto and Yamada reported improved performance with dobutamine in similar conditions. In general, studies comparing the relative effectiveness of dobutamine with that of dopamine and other catecholamines have shown increases in cardiac output after dobutamine as great and sometimes greater than those produced by dopamine.