Maternal and fetal effects of exchange transfusion with a red blood cell substitute

Recent reports have demonstrated the efficacy of Fluosol-DA (20%) as a temporary erythrocyte substitute. We investigated two groups of pregnant ewes that underwent exchange transfusion. In group 1, the animals underwent a nearly total isovolemic exchange of Fluosol-DA (20%) for maternal whole blood; in group 2, the red blood cells were removed and the plasma along with Ringer's lactate was replaced isovolumetrically. Although group 1 animals received 100% oxygen and Fluosol-DA (20%), the maternal arterial Po2 increased to 350 to 400 torr. However, the maternal blood oxygen content decreased during the exchange, with no change in fetal pH, Pco2, or hematocrit. Maternal blood pressure remained stable and there was a 40% to 50% increase in cardiac output and mean pulmonary arterial pressure. During the exchange, the maternal hematocrit decreased from a mean of 32% to 5.5%; the maternal fluorocrit at the end of the exchange was 9%. Throughout the Fluosol-DA (20%) exchange, the proportion of fetal brain oxyhemoglobin as estimated from infrared transcranial transmittance increased, as did the fetal blood Po2 and oxygen content. In group 2, the maternal mean blood pressure decreased, and the hematocrit decreased from a mean of 32% to 8%. Despite an increase in the maternal Po2 to 250 torr, the fetal Po2 and oxygen content decreased in group 2. This investigation demonstrated that Fluosol-DA (20%) exchange of the mother does not impair delivery of oxygen to the fetus under the conditions of the study.