Canadian Journal of Anesthesia, Vol 40, 495-501, Copyright © 1993 by Canadian Anesthesiologists' Society

ARTICLES

Amrinone, in combination with norepinephrine, is an effective first-line drug for difficult separation from cardiopulmonary bypass

JF Hardy, N Searle, M Roy and J Perrault
Department of Anaesthesia, Montreal Heart Institute, Quebec, Canada.

A crucial element for weaning patients from cardiopulmonary bypass (CPB) rests on the selection of an appropriate therapeutic regimen. Amrinone, a phosphodiesterase III inhibitor, combines inotropic support with pulmonary and systemic vasodilatation, without increasing heart rate (HR) or myocardial oxygen consumption. These characteristics should be useful in the failing heart during weaning from CPB. Nineteen patients were included in this prospective, open-labelled, phase IV study when systolic blood pressure (DPAP) > 15 mmHg or central venous pressure (CVP) > 15 mmHg, during progressive separation from CPB. At that moment, CPB flow was increased to alleviate heart failure and amrinone administered as a bolus (0.75 mg.kg-1) followed by an infusion (10 micrograms.kg-1.min-1). Weaning from CPB was then resumed and haemodynamic variables (SBP, DPAP, CVP and HR) were compared with those measured at CPB flow when failure had first occurred. Failure to wean from CPB occurred at 57 +/- 28% of full pump flow. After the amrinone bolus, DPAP and CVP decreased by 20% and 21% respectively. Subsequently, 16 patients required the infusion of norepinephrine (4-8 micrograms.min-1) to maintain a SBP > 80 mmHg. Heart rate remained unchanged after the bolus of amrinone, after separation from CPB, and no arrhythmias were noted. Successful weaning from CPB was possible 12 +/- 8 min after the amrinone bolus. Weaning resulted in a cardiac index similar to that measured pre-bypass. Amrinone is rapidly effective during weaning from CPB and, in combination with norepinephrine, provides the necessary inotropic support during this unstable period.

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