Myocardial recovery after hypothermic arrest

We compared multidose crystalloid hyperkalemic cardioplegic solutions with and without added red cells in 24 canine hearts subjected to 5 hr of arrest at 100 C. All cardioplegic solutions were fully oxygenated at 40 C before delivery. Since blood cardioplegia contained Ca+ + carried over with the red cells, Ca+ + was added to the crystalloid solution in one group. The table below shows the hematocrit (HCT) and ionized Ca + + concentrations of the cardioplegic solutions, and coronary arteriovenous oxygen difference during infusion of cardioplegic solution (AVO2) (ml 02/100 ml). Recovery during reperfusion is shown as percent of prearrest left ventricular function (LVF) and prearrest myocardial ATP concentration. AVO2 during infusion of cardioplegic solution was greater in group 111 than in any other group (p < .008). Percent ATP at 110 min reperfusion was similar in all groups. LVF decreased in groups 1 (p < .0167) and 11 (p < .0167) between 70 and 100 min. The decrease in LVF in group III did not reach significance. LVF in group IV, in which a cardioplegic solution with a Ca+ + concentration similar to that used in group III was used, remained stable from 50 to 100 min of reperfusion. Cardioplegic solution perfusion in the posterior papillary muscle (microspheres) was best maintained in group I1l. The rheologic properties of the cardioplegic solution with the higher hematocrit may account for the greater AVO2 and enhanced posterior papillary muscle perfusion during arrest. However, sustained functional recovery during reperfusion was dependent on the amount of Ca++ in the cardioplegic solution. No beneficial effect on LVF of added red cells was demonstrated beyond the effect of the concomitant addition of Ca+.