EFFECT OF LOW-DOSE POSITIVE INOTROPIC DRUGS ON HUMAN INTERNAL MAMMARYARTERY FLOW

Background. Dobutamine (alpha beta-receptor agonist), enoximone (a typ e III selective phosphodiesterase inhibitor), and epinephrine (an alph a- and beta-mimetic) frequently are used in the perioperative manageme nt of patients undergoing coronary artery bypass grafting. Methods. We performed a double-blind clinical study to compare the effects on int ernal mammary artery free flow of low doses of these three positive in otropic drugs. Thirty patients in whom the left internal mammary arter y was used for coronary artery bypass grafting were randomized into th ree groups. Internal mammary artery free flow and hemodynamic measurem ents were evaluated before and 10 minutes after the intravenous infusi on of dobutamine (3 mu g . kg(-1) . min(-1)), enoximone (200 mu g/kg), or epinephrine (0.05 mu g . kg(-1) . min(-1)). Results. A significant increase in free flow occurred only in the dobutamine group (33 +/- 7 .5 and 42.2 +/- 7.9 mL/min before and after drug infusion, respectivel y; p = 0.013). Comparison of the increase in flow between the groups, however, showed no difference. These drugs, at doses designed to produ ce a positive inotropic effect, caused little increase in the free flo w of the internal mammary artery. Conclusions. The use of dobutamine, enoximone, and epinephrine as low-dose positive inotropic treatments i n the perioperative and postoperative periods of coronary artery bypas s grafting should depend on their positive inotropic effects rather th an their vasodilative effects on the arterial grafts. (C) 1997 by The Society of Thoracic Surgeons.