The use of amrinone and norepinephrine for inotropic support during emergence from cardiopulmonary bypass

Abstract

D ESPITE MAJOR improvements in techniques of myocardial preservation, the low output state (LOS) following cardiopulmonary bypass (CPB) continues to present challenges in the management of cardiac surgical patients. The factors causing LOS include ischemia leading to a stunned myocardium,’ preoperative severe ventricular dysfunction, long aortic cross-clamp times, and poor myocardial preservation. This “post-ischemic global myocardial dysfunction” requires aggressive treatment.’ Considerable controversy exists regarding the optimal agents for inotropit support during emergence from CPB.*,” Many of the studies conducted to evaluate inotropic agents have been carried out several hours and even days after termination of CPB.4-6 Although these data are obtained in a more stable setting, they do not address the problem of immediate post-CPB myocardial dysfunction. Some studies have compared epinephrine, isoproterenol, dopamine, and dobutamine in the post-CPB period.7,8 These sympathomimetics successfully increase cardiac output, but with varying and undesirable side effects, primarily tachycardias and dysrhythmiss.‘.’ Other approaches include combinations of inotropes and vasodilators,’ norepinephrine (NE) and phentolamine,‘” and the use of the intraaortic balloon pump (IABP).” (PHE) or NE was used as primary therapy for the LOS during emergence from CPB. This combination therapy led to significant improvement in cardiac index and blood pressure without any tachyarrhythmias. Two cases are described below and the results in 7 patients are presented.