Tissue osmolality, metabolic response, and reperfusion in myocardial ischemia.

We studied the effect of tonicity of the perfusate during reperfusion after global ischemia, in both the rat and the porcine heart. After 50 min, tissue osmolality increased by about 40 mOsm/kg. Normotonic as well as hypertonic reperfusion resulted in limited areas of "no-reflow". Metabolic restoration after reperfusion was not dependent on the tonicity of the perfusate, nor was recovery of contractility. Hypertonic reperfusion induced a higher coronary flow rate. In porcine hearts, scatter of metabolic data indicated inhomogeneity of reperfused tissue. The results differ substantially from data obtained after reperfusion of regionally ischemic hearts. Reasons for these differences are discussed.