Inotropic therapy for right ventricular failure in newborn piglets: effect on contractility, hemodynamics, and interventricular interaction.

Abstract

To investigate the effect of right ventricular stunning on interventricular relationships in newborn piglets and to determine the effect of three commonly used inotropic treatment strategies. Randomized, placebo-controlled animal study. Aarhus University Hospital, animal laboratory. Twenty-eight newborn (4-d old) farm-bred piglets. Acute right ventricular failure was induced by 10 cycles of alternating 3 minutes of ischemia and reperfusion of the right coronary artery. After right ventricular failure was induced, treatment with epinephrine + milrinone, dopamine + milrinone, dobutamine, or control (saline) was initiated, and the animals were observed for 180 minutes. Right and left ventricular systolic and diastolic variables were measured using pressure-volume loops recorded by conductance catheters. Arterial and central venous pressures were recorded, and cardiac index was determined by placing a flow probe around the pulmonary artery. Whole-body perfusion was evaluated by measuring pH and lactate in arterial blood samples. Induction of right ventricular stunning resulted in decreased ejection fraction (51% ± 4% vs 40% ± 12%, p = 0.0004); caused an interventricular septum deviation, decreased mean arterial pressure (49 ± 10 mm Hg vs 43 ± 11 mm Hg, p = 0.03), and increased blood lactate (1.85 ± 0.6 mM vs 5.79 ± 3.16 mM, p < 0.00001); and led to a decrease in blood pH (7.37 ± 0.08 vs 7.23 ± 0.13, p < 0.00001). A mortality rate greater than 50% was observed in the control group. All inotropic interventions increased contractility significantly in both the left and right ventricle. The effect of dobutamine on right ventricular failure decreased after 30 minutes and was indistinguishable from the control group after 3 hours. Dobutamine-treated animals had lower perfusion pressures and blood pH compared with epinephrine + milrinone and dopamine + milrinone groups. In newborn piglets, dobutamine had a nonsustained effect on right ventricular failure, resulting in decreased contractility and impaired perfusion compared with both dopamine and epinephrine administered in combination with milrinone.