OXYGEN, GLUCOSE, AND LACTATE UPTAKE BY FETUS AND PLACENTA DURING PROLONGED HYPOXEMIA

Our aim was to compare the effects of short (4 h) and prolonged (24 h) periods of reduced uterine blood flow (RUBF) on fetal and placental u ptake of O-2, glucose, and lactate. In pregnant sheep, uterine and umb ilical blood flows were measured under normal conditions and after 4 a nd 24 h of RUBF. A 50% reduction in uterine blood flow caused a 56% re duction in fetal arterial O-2 saturation (Sa(O2)). Umbilical blood flo w increased from 325 +/- 33 to 378 +/- 32 ml.min(-1).kg(-1) (P < 0.05) after 4 h but was not different from pre-RUBF values after 24 h. O-2 uptake by the gravid uterus was not altered by RUBF, due to an increas e (84%) in uterine O-2 extraction. Similarly, uteroplacental and fetal O-2 consumptions and fetal glucose uptake were not affected by RUBF, whereas uteroplacental glucose uptake was significantly reduced after 4 h (by 42%) and 24 h (by 58%) of RUBF. Fetal lactate uptake was great ly reduced from 78.7 +/- 15.5 to -167 +/- 57 mu mol.min(-1).kg(-1) aft er 4 h and to -198 +/- 80 mu mol.min(-1).kg(-1) after 24 h of RUBF; ne gative values indicate placental lactate uptake from the fetal circula tion. Thus, although RUBF significantly reduced fetal Sa(O2), fetal an d uteroplacental O-2 consumptions did not change. In addition, althoug h fetal glucose uptake was not altered by RUBF, during RUBF the placen ta became a major site of lactate clearance from the fetal circulation .