Metabolic recovery after global myocardial ischemia: Effects of blood cardioplegic solutions

OBJECTIVE: To determine the effect of whole blood cardioplegia (WBC) and a mix of crystalloid in blood (CB) hyperkalemic cardioplegic solutions on recovery of the myocardium following global ischemia. DESIGN: Twenty one dogs were placed on normothermic cardiopulmonary bypass, and a pH probe was inserted in the anterior wall of the left ventricle. Global myocardial ischemia was obtained by clamping the ascending aorta until a decrease in myocardial tissue pH of 0.4 units from baseline value was obtained, at which time cardioplegic solutions were perfused over 30 mins. The aorta was then unclamped and 30 mins of reperfusion was allowed. RESULTS: The aortic cross-clamping rime necessary to decrease myocardial tissue pH 0.4 units from baseline averaged 13+/-8 mins. Whereas myocardial tissue pH returned to baseline value (6.9+/-0.1) after an average of 241 mins with cold (15DC) and warm (35 degrees) WBC, it took an average of 48 mins to reach control levels when warm CB solutions were used. Moreover, tissue pH de creased temporarily from 6.97+/-0.35 to 6.77+/-0.31 (P<0.05) at initiation of normothermic myocardial reperfusion in cold WBC protected animals, and myocardial pH remained normal in the warm WBC group but remained severely acidic in warm CB animals (6.6+/-0.3). CONCLUSIONS: Metabolic recovery after global ischemia was faster with WBC cardioplegic protection. Normothermic blood hyperfusion in cold WBC protected animals caused a significant but temporary tissue acidosis.