Effect of fetal or adult red cells on tissue oxygenation and myocardial function in normoxemic newborn lambs.

Twelve newborn lambs less than 48 hr old had their high oxygen affinity blood exchanged for low-affinity fresh adult blood. Tissue oxygenation, hemodynamic status, blood gases, and myocardial function were compared before and after the exchange transfusion. The P50 was increased from 18 to 29 mm Hg after exchange transfusion; pH and hemoglobin levels remained constant; and there was no change in myocardial function, arteriovenous O2 content difference, O2 consumption, or cardiac output. However, mixed venous PO2 was significantly increased with low affinity red cells (33 versus 23 mm Hg).