title: Optimal calcium concentration for a cardioplegic solution and "calcium paradox".
abstract: This study was performed to determine the optimal calcium concentration for a cardioplegic solution and to examine the effect of hypothermia on the occurrence of "calcium paradox." Under cardiopulmonary bypass with moderate hypothermia, 90 min of aortic occlusion was employed, and cardioplegic solutions of different calcium concentrations were infused continuously from the aortic root. The myocardial temperature was kept around 28 degrees C in 36 mongrel dogs (Group A) and 20 degrees C in six dogs (Group B). Calcium concentrations of the infused cardioplegic solutions were 0, 1, 2, 3, 4, and 5 mEq/liter in Group A and 0 in Group B. Hemodynamics, myocardial enzymes, and myocardial ultrastructure were evaluated in each group. In Group A, severe myocardial damage was observed in the hearts perfused with calcium-free solution. In the group employing the solution with 5 mEq/liter of calcium, the left ventricle was extraordinarily contracted during aortic clamping and was unable to survive 60 min after unclamping in all cases. However, in the group with 2 mEq/liter calcium, myocardial function and structure were well preserved. These results suggested that the optimum calcium concentration of a cardioplegic solution was 2 mEq/liter and that hypothermia at 20 degrees C of myocardial temperature prevents "calcium paradox."
mesh_terms: D000818:Animals; D001219:Aspartate Aminotransferases / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D003402:Creatine Kinase / Q000378:metabolism; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006324:Heart Arrest, Induced; D006439:Hemodynamics / Q000187:drug effects; D007036:Hypothermia, Induced; D007473:Ion Channels / Q000187:drug effects*; D008854:Microscopy, Electron; D008929:Mitochondria, Heart / Q000648:ultrastructure; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology
chemical_list: D007473:Ion Channels; D001219:Aspartate Aminotransferases; D003402:Creatine Kinase; D002118:Calcium