Selective distribution of microspheres injected into the umbilical veins and inferior venae cavae of fetal sheep.
To investigate the extent of streaming of umbilical venous blood in the venous and arterial circulations of normal and hypoxic sheep fetuses and to experimentally determine its effect on determinations of blood flow by means of the microsphere method, we injected 15 mu microspheres labeled with different radionuclides into the umbilical veins (UVs) and distal inferior venae cavae (DIVC) of 21 chronically catheterized near-term sheep fetuses. We determined the ratio of the radioactive counts from the UV-injected microspheres to the radioactive counts from the DIVC-injected microspheres (UV/DIVC count ratio) in each fetal tissue in 40 experiments. In 75% of the normal fetuses and 58% of the hypoxic fetuses, UV-injected microspheres streamed preferentially through the foramen ovale to the left atrium and ventricle when compared with DIVC-injected microspheres. Fetal hypoxia was associated with a significant decrease in the extent of preferential streaming. In the arterial circulation, we found no evidence for preferential streaming of UV-injected and DIVC-injected microspheres.
D000818:Animals; D001775:Blood Circulation; D001783:Blood Flow Velocity; D005260:Female; D005311:Fetal Hypoxia / Q000503:physiopathology; D005333:Fetus / Q000502:physiology*; D008863:Microspheres; D011247:Pregnancy; D012756:Sheep; D014471:Umbilical Veins / Q000502:physiology*; D014682:Vena Cava, Inferior / Q000502:physiology*