Effect of graded umbilical cord compression in fetal sheep at 0.6-0.7 gestation.
To define responses of immature fetuses to asphyxia, we occluded the umbilical cord of 11 chronically instrumented fetal sheep at 82-94 days gestation and measured hemodynamic and catecholamine responses. The fetuses became acidemic, hypoxemic, and hypercarbic: arterial pH and PO2 decreased from 7.36 +/- 0.04 and 22 +/- 3 Torr to 7.10 +/- 0.04 (mean +/- SD, P less than 0.01) and 15 +/- 4 Torr (P less than 0.01), respectively, and PCO2 increased from 56 +/- 5 to 86 +/- 8 Torr (P less than 0.01) when umbilical blood flow was reduced by 75-88%. This degree of reduction in umbilical blood flow decreased cardiac output from 606 +/- 101 to 247 +/- 67 ml.min-1.kg-1 (P less than 0.01) and blood flow to hepatic, renal, musculoskeletal, and pulmonary vascular beds. Plasma norepinephrine concentrations increased from 1,557 +/- 975 to 16,718 +/- 14,672 pg/ml (P less than 0.05) with a 75-88% reduction, but mean arterial blood pressure did not increase. The absence of a hypertensive response probably relates to the decrease in cardiac output. These data indicate that asphyxia severely compromises cardiac output and organ perfusion in the midgestation fetus.
Cardiovascular Research Institute, University of California, San Francisco 94143-0544.
H S
HS
Iwamoto
E
E
Stucky
C M
CM
Roman
D000818:Animals; D001774:Blood Chemical Analysis; D002302:Cardiac Output; D003251:Constriction, Pathologic / Q000503:physiopathology; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D005865:Gestational Age; D006352:Heart Ventricles; D006439:Hemodynamics; D008102:Liver Circulation; D009638:Norepinephrine / Q000494:pharmacology; D010101:Oxygen Consumption; D012039:Regional Blood Flow; D012756:Sheep / Q000196:embryology*; D014470:Umbilical Cord / Q000503:physiopathology*; D014682:Vena Cava, Inferior / Q000503:physiopathology; D014683:Vena Cava, Superior / Q000503:physiopathology
D009638:Norepinephrine