Distribution of the circulation in the normal and asphyxiated fetal primate

Abstract

Term primate fetuses had average cardiac outputs of 445 ± 90 c.c. per millimeter per kilogram, umbilical blood flows of 208 ± 20 c.c. per millimeter per kilogram, and O2 consumptions of 7 ± 2 c.c. per millimeter per kilogram. There was preferential streaming of ductus venosus (DV) blood to the brain and heart and negligible shunting of superior vena cava (SVC) blood through the foramen ovale. The largest proportion of the cardiac output was distributed to the brain and placenta. The blood flow to the midbrain, brainstem, and cerebellum was significantly higher than that to the cerebral cortex. Asphyxia induced by maternal hypoxia compatible with fetal survival led to mixed acidosis; decreased O2 consumption, umbilical blood flow, and cardiac output; marked shunting of SVC blood through the foramen ovale for distribution to the brain and heart; and, an increase in the proportion of the reduced umbilical blood flow going through the DV. The blood flow to the heart, brain, and adrenal per gram of tissue was maintained by an increase in the distribution of cardiac output to these organs. The placental and pulmonary flows decreased.