Abstract
This study evaluated the effects of milrinone, adrenaline and dobutamine with pressure-volume loops and isolated atrial tissue.
Agonist dose-response curves to incremental drug infusions were acquired in 11 anesthetised rabbits using pressure-volume loops and preload recruitable stroke work indicated contractility. Agonist concentration-response curves were completed in eight guinea pig isolated atria, for effects on atrial rate and force.
Adrenaline and dobutamine increased contractility (P=0.006 and 0.044), whereas milrinone did not (P=0.895). Only adrenaline increased myocardial stiffness (P<0.001). Milrinone decreased vascular resistance (P<0.001) and elicited the greatest fall in mean arterial pressure (P<0.001) and increased ejection fraction (P<0.001). Adrenaline decreased heart rate (P<0.001), whereas dobutamine and milrinone increased it (P=0.006 and 0.011). Milrinone increased the force of left atrial contraction, but its inotropic effect was weak and significantly less than with dobutamine and adrenaline (P <0.001).
Adrenaline acted as an inoconstrictor, dobutamine an inodilator and milrinone predominantly a vasodilator.