Validation of the antipyrine method for measuring fetal umbilical blood flow.

Vinyl catheters were inserted into an umbilical vein, a hindlimb vein and either an umbilical or dorsalis pedis artery in 9 lamb fetuses with gestational ages of 110 to 147 days. The lambs were then delivered from the uterus, but placental flow was maintained. Cannulating electromagnetic flow transducers were inserted into both umbilical veins. Antipyrine solution was constantly infused into the hindlimb vein, and after equilibration, umbilical blood flow was calculated by the Fick method. The values for umbilical flow measured by the antipyrine technique were comparable with those recorded simultaneously with electromagnetic flowmeters. There was also no difference in antipyrine concentrations in the peripheral and main umbilical veins. The study thus validates the use of the Fick method with continuous antipyrine infusion for measuring fetal umbilical blood flow. ADDITIONAL