High 2,3-DPG Blood Cardioplegia and Myocardial Preservation During Cardiopulmonary Bypass

Abstract

Blood may provide superior cardioplegia compared with crystalloid cardio plegic solution. However, the results are controversial. This may be due to a leftward shift of the hemoglobin (Hb)-02 dissociation curve induced by hypo thermia, increasing the oxygen affinity for Hb. This effect may negate the po tential benefit of blood cardioplegia. The oxygen affinity for Hb can be decreased by increasing the red cell 2,3-diphosphoglycerate (2,3-DPG), and hence, more oxygen can be delivered to the myocardium. The present investiga tion was undertaken to study the effects of 2,3-DPG-enriched blood cardiople gia on the functional recovery of the myocardium and changes in the coronary sinus red blood cell (RBC) adenosine-triphosphate (ATP), lactate, and RBC DPG after one and a half hours of reperfusion following one hour of ischemic cardiac arrest in dogs. The dogs were divided into three groups: crystalloid (CR); stored blood (SB), and high 2,3-DPG blood (HDPG) cardioplegic groups. Incubation of canine RBC in phosphoenal pyruvate (PEP) led to a 36% increase in DPG and a rightward shift in the Hb-O2 dissociation curve. There was a 4 mm Hg shift in the P50. When compared with the CR group, there was a significant decrease in the cardiac index (CI) and left ventricular work index (LVWI) and a significant increase in the total systemic vascular resistance (TSVR) in the SB group. The CI and LVWI of the HDPG group were similar to those of the CR group, but the TSVR was significantly greater in the former group. The LVWI was significantly greater and the TSVR smaller in the HDPG group as com pared with those in the SB group. The coronary sinus, lactate, and RBC 2,3- DPG were never significantly different at any point among the three groups, although a trend toward a decrease in lactate with the HDPG group was ob served. There was no significant difference in the RBC ATP content from the three different groups except during initial period of ischemic arrest when RBC ATP content of HDPG group was greater than that in CR group. There was a decrease in the Hb content of the blood in all three groups. The decreases were similar in all the groups except during the postpump period, when the Hb con tent of the HDPG and SB groups was higher than that of the CR group. These results suggest that stored blood was inferior to crystalloid and HDPG cardioplegia in preserving the myocardial function and cardiac metabolism. However, HDPG cardioplegia was not better than CR cardioplegia in preserv ing the cardiac function. Better preservation of cardiac function with HDPG as compared with the SB group might be due to a rightward shift in the Hb-O2 dissociation curve.