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.
Iwamoto
H S
HS
Cardiovascular Research Institute, University of California, San Francisco 94143-0544.
Stucky
E
E
Roman
C M
CM
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