CHARACTERIZATION OF ENERGY-METABOLISM AND BLOOD-FLOW DISTRIBUTION IN MYOCARDIAL-ISCHEMIA IN HEMORRHAGIC-SHOCK

To characterize the mechanisms for myocardial ischemia induced by hemo rrhagic shock, 29 dogs were subjected to hemorrhage at a mean aortic p ressure (MAoP) of 30-60 mmHg. After 10 min of hemorrhage, the beating hearts were rapidly cross sectioned and freeze clamped to visualize th e two-dimensional distribution of myocardial ischemia with NADH fluore scence (NADH-F) in 22 dogs. NADH-F was developed at an MAoP of 40 mmHg or less and involved both the subendocardial half and the subepicardi al half of the left ventricle [34 +/- 14 vs. 20 +/- 14% (P < 0.05) and 65 +/- 16 vs. 52 +/- 15% (not significant) of the cross-sectional are a of the left ventricular slice at MAoP levels of 40 and 30 mmHg, resp ectively]. Magnified NADH-F photography demonstrated heterogeneously d istributed microischemic lesions with a columnar shape (mode of short- axis length, 60-80 mu m). NADH-F-guided microsamplings revealed higher NADH and lactate concentrations in a positive NADH-F area than those in a negative NADH-F area. The ratio of endocardial to epicardial bloo d flow was maintained at a relatively high level (1.07 +/- 0.07 and 0. 88 +/- 0.07 at MAoP levels of 40 and 30 mmHg, respectively; n = 7 dogs ), and the reactive hyperemia was preserved as well. In conclusion, my ocardial ischemia in early hemorrhagic shock was characterized by mini mal transmural heterogeneity and marked heterogeneity between contiguo us small regions.