Influence of noradrenaline and temperature on the isolated perfused rat heart

Myocardial protection during open heart surgery is achieved by general cooling and cold cardioplegia. However sympathetic activation during the operation causes raised circulating catecholamine levels that might negatively influence the myocardial metabolism. Moreover, local liberation of catecholamines, in "poorly perfused' regions of the myocardium in patients with ischemic heart disease, might occur. In respect of these problems, we studied the influence of noradrenaline at different temperatures on the isolated perfused rat heart. The temperatures chosen were: 10, 20, 32, 37 and 39 degrees C. The results show clearcut adverse effect of noradrenaline at 32 degrees and higher, on metabolism and hemodynamic performance. At lower temperatures there still seem to be an adverse effect of noradrenaline although not statistically significant. The results of this study indicates the importance of presurgical myocardial protection especially of badly perfused myocardial areas. Such protection could be accomplished by beta-blockade and/or loading of the myocardium with glycogen by glucose-insulin-potassium infusion.