Amrinone Reverses Cardiac Depression and Augments Coronary Vasodilation with Isoflurane in the Isolated Heart

Amrinone is a positive inotropic and vasodilatory agent and may be administered during anesthesia with isoflurane. The authors' aims were 1) to examine if amrinone produces coronary artery vasodilation through an increase in metabolic demand or through a direct vasodilatory effect or through both and 2) to test if amrinone attenuates cardiac depression and enhances coronary artery vasodilation produced with exposure to isoflurane. The effects of these drugs were examined in 11 isolated perfused guinea pig hearts. Variables measured were: heart rate (HR), atrioventricular conduction time (AVCT), isovolumetric peak left ventricular pressure (LVP), coronary flow, percent O2 extraction, myocardial O2 consumption (MVO2), and the ratio of O2 delivery (DO2) to MVO2. Each heart was exposed for 10-min periods to 10, 50, 100, and 500 microM amrinone alone, and to 0.5 or 1% isoflurane before, during, and after amrinone. Initial control values were: heart rate 216 +/- 5 beats per min; AVCT 56 +/- 1 ms; peak LVP 86 +/- 3 mmHg; coronary flow 6.3 +/- 0.3 ml.min-1.g-1 (11.4 +/- 0.7 ml.min-1.g-1 with adenosine bolus), percent O2 extraction 52 +/- 3%; DO2 107 +/- 3 microliters.min-1.g-1; MVO2 56 +/- 4 microliters.min-1.g-1; and DO2/MVO2 1.75 +/- 0.08. Amrinone 500 microM alone increased (P less than 0.05) heart rate by 9%, LVP by 13%, coronary flow by 18%, and MVO2 by 23%; AVCT decreased by 3%.(ABSTRACT TRUNCATED AT 250 WORDS)