Circulatory and metabolic effects of anemia in hyperinsulinemic ovine fetuses.

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Infants born to women with poorly controlled diabetes mellitus have an increased incidence of perinatal asphyxia, cardiovascular abnormalities, elevated catecholamines, and sudden fetal death. Although hyperinsulinemic fetuses of diabetic women often exhibit polycythemia, they may also develop anemia because of pregnancy- and/or delivery-related complications. Experimental fetal hyperinsulinemia results in cardiovascular changes and a surge in catecholamines. We hypothesized that reductions in fetal O2 availability via anemic hypoxia limits O2 transport and compromises the hemodynamically and metabolically stressed but compensated hyperinsulinemic fetus. Chronically catheterized fetuses receiving insulin (n = 9) or placebo (n = 5) for 48 h were rendered anemic by an isovolemic exchange transfusion. In the hyperinsulinemic state, anemic-hypoxia augmented the insulin-mediated surge in norepinephrine concentration and increases in blood flow to brain, heart, and adrenal glands. Insulin-related increase in the combined ventricular output was sustained during anemia. O2 delivery to the fetus decreased, extraction increased, and O2 uptake did not change. Regional O2 delivery to the brain, kidney, gastrointestinal tract, muscle, fat, pancreas, spleen, and carcass decreased. Hyperinsulinemic ovine fetus exposed to anemic hypoxia demonstrated an accentuated surge in norepinephrine, a sustained increase in the combined ventricular output, preservation of systemic O2 uptake, and compromised regional O2 delivery to certain vascular regions. We conclude that the hyperinsulinemic fetus was able to compensate for anemic hypoxia by increased or sustained regional vascular perfusion.