The Effect of Fetal Exchange Transfusions with Adult Blood upon Fetal Oxygenation

Abstract

ExtractIntrauterine exchange transfusions were conducted i n fetal sheep using a d u l t sheep a s donors. I ndwelling catheters i n t h e fetus permitted sampling of blood for 8 to 36 days following t h e transfusion.I n t h e first days after t h e procedure there was a decreased oxygen affinity of umbilical blood, a n increase of a b o u t 5 mm Hg i n umbilical venous 0, tension, and a decrease of a b o u t 30 % in 0, saturation. I n t h e following weeks there was a g r a d u a l r e t u r n of 0, a f i n i t y , PO,, a n d oxygen saturation to normal. In all of t h e experiments there was a good correlation between t h e 0, affinity of umbilical blood a n d t h e percentage of a d u l t cells present. T h i s correlation indicated t h a t a d u l t cells retained a n o r m a l 0, dissociation curve even after weeks of exposure to t h e n e w environment. Despite a n increased umbilical venous PO,, t h e fetal reticulocyte c o u n t increased significantly after transfusion, b u t t h e oxygen capacity of umbilical blood remained within n o r m a l limits. SpeculationThese studies suggest t h a t t h e correction of fetal a n e m i a i n erythroblastosis fetalis b y t h e use of fetal blood instead of a d u l t blood would produce a greater increase i n t h e a m o u n t of hemoglobin c a p a b l e of carrying oxygen a t t h e low oxygen tensions characteristic of t h e fetal circulation.The first successful intrauterine transfusion of a human fetus was reported by LILEY in 1963 [5]. Since that time many fetal transfusions have been performed for treatment of the fetus severely affected by erythroblastosis. Despite a n expanding literature about this procedure, there have been no studies reported in experimental animalsevaluatingsomeof thesurgical and physiological problems encountered. One of the most obviousphysiologic handicaps imposed upon the fetus that undergoes transfusion is the replacement of fetal cells with adult cells having a much lower oxygen affinity.This study was undertaken in order to determine the effects upon umbilical blood oxygenation of substituting adult whole blood for fetal blood within the circulation offetal lambs. Experiments were performed in animal preparations in which an indwelling catheter was implanted within the umbilical vein at the time of the exchange transfusion and in which the pregnancy was allowed to continue to the point of delivery. Such preparations made possible the determination of the changes in respiratory gases within the same fetus for some weeks following intrauterine exchange transfusion.

Extracorporeal Support of the Fetal Lamb Simulating <i>in utero</i> Gas Exchange

“…At a Pao" of 21 mm Hg, the arterial blood is 66% saturated in utero but only 36% saturated during bypass. Battaglia et al [1969] report a similar trend for umbilical venous saturation after a fetal exchange transfusion using adult red blood cells. The reduced hematocrit and the shift of the Oa dissociation curve, could reduce the oxygen content of the arterial blood by over 50%, even though the blood is maintained at an appropriate Pao._, of 21 mm Hg.…”

Suppression of compensatory erythropoiesis in hemolytic disease of the fetus and newborn due to intrauterine transfusions

“…16 Experiments in sheep showed that exchange transfusion in sheep fetuses using adult sheep blood resulted in an overall decrease in oxygen affinity and saturation and, interestingly in view of our results, an increased reticulocytosis, whereas hemoglobin levels remained constant. 17 Adult hemoglobin is, however, also known to provide better peripheral tissue oxygenation compared with fetal hemoglobin, 16 which may result in a local reduction of hypoxic stimulus, causing reduced EPO production, which might explain the observed drastic decline in reticulocytes. In our institute, fetal EPO levels are not routinely measured.…”

Erythrocyte Lipids in Infants with Low Birth Weights

“…One difference of major importance is in the oxygen dissociation characteristics of fetal cells which may be more closely related to the presence of a fetal membrane than fetal homoglobin [22]. Although adult cells transfused into the fetus may acquire some lipid characteristics of fetal cells [17], they retain an adult dissociation curve [4]. It would appear unlikely that this characteristic of fetal membrane is directly dependent on structural lipids which are susceptible to alteration by the plasma environment as previously postulated [7,16].…”