Circulatory and metabolic effects of hypoxia in the hyperinsulinemic ovine fetus.

Abstract

Fetuses of women whose diabetes is poorly controlled often exhibit hypoxemia and elevated catecholamine concentrations at birth. In the ovine fetus, experimental hyperinsulinemia results in hypoxemia, elevated catecholamine concentrations, and hemodynamic changes. Limited oxygen availability occurring during pregnancy-related complications and/or delivery may present an additional risk to the hyperinsulinemic fetus. In this study, we tested the hypothesis that hypoxia induced via acutely limiting oxygen availability compromises the hemodynamically and metabolically stressed but compensated hyperinsulinemic ovine fetus. Fetuses receiving insulin (n = 8) or placebo (n = 5) for 48 h were exposed to maternally induced hypoxia. Hypoxic hypoxia was associated with a surge in catecholamines in the hyperinsulinemic fetuses. During hypoxia, this group exhibited insulin-related sustained increases in the combined ventricular output and fetal body blood flow, accentuation of the prior insulin-related increase in blood flow to the heart, decreased systemic oxygen delivery, accentuation of the insulin-related increased oxygen extraction, reductions in the insulin-related increased systemic oxygen uptake, sustained increases in regional oxygen delivery to the heart and adrenal glands, reductions in the insulin-related increased delivery to the carcass, and decreased oxygen delivery to the kidneys and gastrointestinal tract. We conclude that, in the hyperinsulinemic ovine fetus, hypoxic hypoxia attenuates the hyperinsulinemia-mediated increased systemic oxygen uptake. Regional oxygen transport is preserved to vital regions (brain, heart, and adrenal glands) by increased perfusion and compromised to certain other regions (kidneys and gastrointestinal tract), because the increases in perfusion are insufficient to offset the limited oxygen availability.