Endocrinologic and biophysical responses to prolonged (24-hour) hypoxemia in fetal goats

Abstract

The purpose of this study was to observe some fetal endocrinologic and biophysical responses to prolonged (24-hour) nonacidemic hypoxemia in fetal goats. Endocrinologic and biophysical changes during continuous infusion of nitrogen into the maternal trachea were examined in six chronically instrumented goat fetuses at 123 to 131 days' gestation. We measured arginine vasopressin, adrenocorticotropic hormone, cortisol, epinephrine, and norepinephrine as endocrinologic parameters and fetal heart rate, fetal blood pressure, and fetal breathing movements as biophysical parameters. Fetal arterial PO2 declined from 25.1 +/- 2.1 mm Hg at baseline to 16.8 +/- 0.9 mm Hg at 1 hour of hypoxemia and remained at this level (p < 0.05). Arginine vasopressin, adrenocorticotropic hormone, and epinephrine initially rose in response to hypoxic stress, gradually declined, and by 24 hours were not significantly different from control values. Cortisol and norepinephrine remained significantly elevated through the experiments. Fetal breathing movements as a percentage of total time were 34.9% +/- 1.2% at baseline, 12.9% +/- 3.7% at 1 hour, and 70% to 80% of control values from 4 hours. Fetal heart rate was significantly reduced for the first 10 minutes, then progressively became tachycardiac thereafter. Systolic fetal blood pressure was significantly elevated for only 30 minutes. Arginine vasopressin, adrenocorticotropic hormone, and epinephrine of the endocrinologic parameters and fetal heart rate, fetal blood pressure, and fetal breathing movements are normalized during prolonged nonacidemic hypoxemia in fetal goats.