Preservation of myocardial high-energy phosphates in open-heart surgery with deep general hypothermia and multidose crystalloi/d cardioplegia

Myocardial energy metabolism during deep general hypothermia (20°C) and multidose crystalloid cardioplegia, and also during subsequent reperfusion, was studied in eight pat ients undergoing isolated aortic valve replacement. Six serial transmural biopsy samples from the left ventricular apex were analyzed for high-energy phosphates and their degradation products. Reductions in ATP, total adenine nucleotide content and energy charge were insignificant during cardioplegia, as were changes in adenosine and uric acid concentrations. During reperfusion, however, there was slight but significant reduction in total adenine nucleotide content, despite adequate oxygenation as indicated by reversal of lactate accumulation. These observations suggest that the reperfusion phase is accompanied by metabolic aberrations which are not overcome by good oxygenation in relation to the metabolic rate.