Oxygen transport in congenital heart disease: influence of fetal hemoglobin, red cell pH, and 2,3 diphosphoglycerate

Abstract

In older children suffering from cyanotic heart disease an adaptive increase in O2 capacity, 2,3 DPG, and P50 occurs. In vivo the 2,3 DPG increase in hypoxemia appears to be controlled by the increased intraerythrocytic pH which, in turn, depends on the low O2 saturation of hemoglobin. In the first weeks of life 2,3 DPG is not elevated in infants with cyanotic heart disease because the low plasma pH frequently found in these babies is balancing the effect of hypoxemia on red cell pH. During hypoxemia, oxygen delivery to tissues depends on the O2 capacity rather than on the O2 affinity. Therefore, an insufficient increase of RBC 2,3 DPG and of blood P50 in response to hypoxemia may not represent a serious disadvantage. Low hemoglobin concentration, however, must be considered a serious cause of hypoxia.