STUDIES ON MYOCARDIAL REPERFUSION INJURY .1. FAVORABLE MODIFICATION BY ADJUSTING REPERFUSATE PH

  • 1 January 1977
    • journal article
    • research article
    • Vol. 82  (1) , 149-155
Abstract
This study tests the hypothesis that postischemic myocardial depression can be reduced by providing an initial reperfusate pH which is appropriate for myocardial temperature, i.e., metabolic systems function optimally when pH is kept slightly alkaline to the neutral point, which changes with temperature in concordance with the pK of water. Ten dogs underwent 1 h of ischemic arrest with topical hypothermia (intramyocardial temperature 16 .+-. 2.degree. C). The initial reperfusate (500 cc of blood from the extracorporeal circuit) was infused (100 cc/min) into the proximal aorta just before removing the cross-clamp. Reperfusate pH was kept at 7.4 in 5 dogs (control) and raised to 7.8 with THAM [tris (hydroxymethyl) aminomethane] in 5 dogs. Measurements 30 min after reperfusion showed that raising reperfusate pH to 7.8 resulted in higher subendocardial blood flows (109 .+-. 20 vs. 61 cc .+-. 8 cc/100 g per min), redistribution of postischemic blood flow toward the subendocardium (endocardial/epicardial flow 1.25 .+-. 0.1 vs. 1.0 .+-. 0.03), higher left ventricular O2 uptakes (0.046 vs. 0.033 cc/100 g per beat), better postischemic left ventricular compliance (56 .+-. 3% more compliant) and improved left ventricular performance (88 .+-. 7% recovery vs. only 57 .+-. 3% recovery at pH 7.4). Postischemic edema (2% water gain) was unchanged by pH modification. Initial reperfusion with the appropriate pH provides an optimal condition for restoration of cellular metabolism, counteracts the acidosis of ischemia and improves postischemic left ventricular blood flow, distribution, O2 uptake, compliance and performance.

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