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[Effect of catecholamine on reperfused myocardium following hypothermic global ischemia].

This study was aimed to evaluate the effect of catecholamine on the myocardium reperfused after hypothermic global ischemia, by changes of hemodynamics, biochemistry and ultrastructure. Under cardiopulmonary bypass (CPB) at flow rate 80 ml/kg/min., the aorta was clamped for 60 min. at 28 degrees C of myocardial temperature and reperfused for 60 min. in 26 mongrel dogs. They were divided into 4 groups by infusion of physical saline solution (control), epinephrine 1 microgram/kg/min. (group 1), epinephrine 0.1 microgram/kg/min. (group 2) and dobutamine 5 micrograms/kg/min. (group 3) during reperfusion. The hemodynamic parameters and myocardial isoenzyme (m-AST, MB-CPK) of coronary sinus venous blood were measured before CPB, 30 and 60 min. after declamp. The myocardial adenosine triphosphate (ATP), creatine phosphate (CP), water content, tissue Ca content and fine structure with score of mitochondrial membrane and cristae were examined in epicardium and endocardium at the end of experiment. Hemodynamic parameters after declamp were higher in group 1, 2 and 3 than control (p less than 0.05). The water content and tissue Ca content in group 1 were higher than control. The ATP of endocardium was lowest but CP was no significant difference among four groups. The mitochondrial score in group 1 was lower than control. These data suggest that epinephrine and dobutamine increase hemodynamics and tissue Ca content on the reperfused myocardium following 60 min. of hypothermic global ischemia, but they do not improve depletion of ATP and disruption of myocardial ultrastructure. High dose of epinephrine accentuates ischemic damage of reperfused myocardium after hypothermic global ischemia.