CARDIOVASCULAR EFFECTS OF DIBUTYRYL-CYCLIC-AMP AND MILRINONE UNDER RIGHT HEART BYPASS IN ANESTHETIZED DOGS

To compare the cardiovascular effects of dibutyryl cyclic AMP (DBcAMP) and milrinone, we used the right heart bypass method in intact anesth etized dogs. The preload of the left ventricle was maintained constant throughout the experiment. Therefore, the effects of DBcAMP and milri none on cardiac contractility and afterload of the left ventricle were investigated respectively without preload influence. DBcAMP and milri none exhibited marked positive chronotropic-, positive inotropic-, vas odilative- and diuretic-activity. DBcAMP expressed these effects gradu ally and continuously, whereas milrinone expressed its pharmacological actions rapidly, but for a short duration of time. Both the afterload -reducing and the cardiac contractile force-enhancing activities of DB cAMP were longer lasting than those of milrinone. Mean arterial pressu re was not altered by DBcAMP infusion, whereas it was increased signif icantly (p<0.05) by milrinone infusion. The results of this study sugg ested that DBcAMP appeared to be indicated when there is a need to inc rease cardiac output by reducing afterload and increasing cardiac cont ractile force gradually and continuously. On the other hand, milrinone would seem to be indicated when the goal is to raise blood pressure r apidly and to increase cardiac output simultaneously.