ENDOCRINOLOGIC AND BIOPHYSICAL RESPONSES TO PROLONGED (24-HOUR) HYPOXEMIA IN FETAL GOATS

OBJECTIVE: The purpose of this study was to observe some fetal endocri nologic and biophysical responses to prolonged (24-hour) nonacidemic h ypoxemia in fetal goats. STUDY DESIGN: Endocrinologic and biophysical changes during continuous infusion of nitrogen into the maternal trach ea were examined in six chronically instrumented goat fetuses at 123 t o 131 days' gestation. We measured arginine vasopressin, adrenocortico tropic hormone, cortisol, epinephrine, and norepinephrine as endocrino logic parameters and fetal heart rate, fetal blood pressure, and fetal breathing movements as biophysical parameters. RESULTS: Fetal arteria l Po-2 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). Argi nine vasopressin, adrenocorticotropic hormone, and epinephrine initial ly rose in response to hypoxic stress, gradually declined, and by 24 h ours were not significantly different from control values. Cortisol an d norepinephrine remained significantly elevated through the experimen ts. 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 con trol values from 4 hours. Fetal heart rate was significantly reduced f or the first 10 minutes, then progressively became tachycardiac therea fter. Systolic fetal blood pressure was significantly elevated for onl y 30 minutes. CONCLUSION: Arginine vasopressin, adrenocorticotropic ho rmone, and epinephrine of the endocrinologic parameters and fetal hear t rate, fetal blood pressure, and fetal breathing movements are normal ized during prolonged nonacidemic hypoxemia in fetal goats.