Regional myocardial metabolism and electrolyte balance during acute ischemia in dogs.
The relationships among regional (ischemic and nonischemic) myocardial extracellular (coronary venous) potassium concentration, potassium-sodium concentration ratio, acid-base balance, and metabolism of glucose and lactate were evaluated in 14 anesthetized dogs in which ischemia was produced by transitory left anterior descending coronary artery (LAD) occlusion. Coronary blood samples were obtained from the specific regions by using coronary arterial and venous catheters placed directly into the vessel supplying (or draining) that region. During ischemia, in coronary venous blood sampled from the ischemic area, pH decreased, and PCO2, base deficit, potassium concentration, and the potassium-sodium ratio increased. In LAD venous blood samples obtained during LAD occlusion, the percentage change in potassium concentration was inversely related to the percentage change in PCO2 (r = -0.634, P < 0.05), but not to the percentage change in hydrogen ion concentration (r = -0.339, P > 0.05). During ischemia, arteriovenous O2 content difference in the LAD region increased from 8.54 +/- 0.73 vol % to 10.71 +/- 0.73 vol %; lactate extraction became negative (indicating net production), values decreasing from 27.76 +/- 4.49% to -138.10 +/- 16.81% (P < 0.05); and glucose extraction increased from 14.57 +/- 2.88% to 19.01 +/- 6.06% (0.05 < P < 0.1). These observations indicate that efflux of potassium from the myocardium during ischemia is linked to tissue hypoxia, increased glucose extraction, lactate production, and extracellular acidosis. A further contributor to potassium release, failure of the normal membrane-bound, energy-requiring ion pump, cannot be excluded by these data. With the model used in this study, blood can be sampled from discrete regions of the heart, which enables the study of interactions between pharmacologic agents, such as anesthetics, and the metabolic abnormalities produced by acute ischemia.
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Department of Anesthesiology, University of Florida College of Medicine, Gainesville, USA.
Rush
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Davis
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D000136:Acid-Base Equilibrium; D000818:Animals; D004285:Dogs; D005947:Glucose / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*
D019344:Lactic Acid; D005947:Glucose; D011188:Potassium