Glucose uptake in the placenta, fetal brain, heart and liver related to blood flow redistribution during acute hypoxia.

AIM

We used positron emission tomography (PET) with radioactive glucose (F-18-Fluor-Deoxglucose [FDG]) to investigate whether acute maternal hypoxemia causes alterations of glucose uptake of fetal organs and the placenta.

MATERIAL AND METHODS

Investigation was performed under normal conditions and acute hypoxemia in 16 fetal sheep between 108 and 130 days of gestation. Maternal sheep were ventilated with 1.0-1.5% isoflurane/O(2) /N(2) O during whole scanning procedure. Acute hypoxia was induced by reducing O(2) in a ventilated gas mixture to achieve maternal arterial O(2) saturation at a constant level of about 75% baseline. Doppler ultrasound blood flow measurements were performed in the ductus venosus (DV), umbilical artery (UA) and vein (UV). Fetal blood samples were taken by cordocentesis of UV. Dynamic positron emission tomography combined with computed tomography (PET-CT) scans of fetuses were acquired over 60 min after intravenous injection of 300 MBq FDG in the mother. Relative FDG uptake in the fetal brain, heart, and liver was determined on summed images from 40-60 min using manually defined volumes of interest (VOI) normalized to mean FDG uptake in placentomes.

RESULTS

Placental blood perfusion reduced significantly from 416.5 ± 116.4 mL/min to 253.5 ± 170.5 mL/min (mean ± SD) during hypoxia. Placental blood supply to the liver decreased from 79.5 ± 14% to 41.1% (P = 0.0001), while DV/UV ratio increased. FDG uptake of the placenta was not changed during hypoxia. Relative FDG uptake in the fetal heart was strongly increased under hypoxia (P = 0.019), whereas it did not differ in the fetal brain and liver.

CONCLUSION

Fetal hypoxia is associated with decreased placental perfusion and liver blood supply. However, glucose uptake was not significantly decreased in the placenta and liver.