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HOME > Acute Crit Care > Volume 20(1); 2005 > Article
Original Article Effects of Amrinone and Dobutamine on Regional Myocardial Function and Oxygen Balance in Normal and Stunned Myocardium in Dogs
Jun Suh Park, Jong Eun Park, Sung Tae Jeong, Seongwook Jeong, Sung Su Chung, Kyung Yeon Yoo

1Department of Anesthesiology and Pain Medicine, Chonnam National University Medical School & Hospital, Korea.
2Research Institute of Clinical Medicine, Chonnam National University Medical School & Hospital, Korea.
3Department of Anesthesiology, Chonnam National University School of Dentistry, Gwangju, Korea.
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We examined the effects of amrinone and dobutamine on regional mechanical function, coronary blood flow (CBF), and myocardial oxygen consumption (MVO2) in normal and stunned myocardium in an open-chest canine model.
Dogs were instrumented to measure aortic and left ventricular pressures, pulmonary and left anterior descending (LAD) coronary blood flows, and subendocardial segment length in the region supplied by LAD. Incremental doses of either amrinone (2~10microgram/ml of LAD flow, n=13) or dobutamine (0.05~0.375microgram/ml of LAD flow, n=14) were directly infused into a coronary artery before (normal) and after a 15 min of LAD occlusion and subsequent 30 min-reperfusion (stunned). Percent segment shortening (%SS) and percent post-systolic shortening (%PSS) were evaluated. Myocardial extraction of oxygen (EO2) and lactate (Elac) was calculated. RESULTS: Amrinone or dobutamine in the normal myocardium caused dose-dependent increases in %SS that were comparable (range, 20~40%) but had no effect on %PSS. MVO2 increased in parallel with %SS for both amrinone and dobutamine. With amrinone, CBF increased more than MVO2, resulting in a modest decrease in EO2, whereas with dobutamine, CBF increased in proportion to MVO2, resulting in no change in EO2. After the ischemia and reperfusion, %SS and Elac were reduced, but similar %SS and CBF responses to both agents were observed, except that both agents caused progressive reductions of %PSS. CONCLUSIONS: These results indicate that both amrinone and dobutamine exert positive inotropic effects in normal and stunned canine myocardium. It is also indicated that amrinone causes direct coronary vasodilation, which is not affected by ischemia and reperfusion, while dobutamine has no direct effect on coronary vascular tone in either normal or stunned myocardium.

ACC : Acute and Critical Care