Catecholamines in arterial and venous umbilical blood: placental extraction, correlation with fetal hypoxia, and transcutaneous partial oxygen tension

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Abstract
In 34 parturient women the levels of free epinephrine (E), norepinephrine (NE) and dopamine (D) were determined by a radioenzymatic method using maternal venous and umbilical arterial and venous blood. The study was conducted to investigate the relationship between fetal catecholamines and hypoxia, fetal heart rate (FHR), and transcutaneous pO2 (tcpO2). The placental catecholamine extraction rates were also calculated. The NE concentrations (10,200 pg/ml) and the E concentrations (1120 pg/ml) in the fetal arterial blood were highly elevated with mean values increased 4-fold over umbilical vein values. Compared with the maternal venous blood, NE values were increased 20-fold, and E values 10-fold. Highly significant correlations were found between fetal arterial NE concentrations and the 1-minute APGAR score, pH and base deficit in the umbilical artery and alterations of the FHR (deceleration area, baseline FHR). A significant rise in NE was only found with additional tachycardia which is often associated with a loss of oscillation amplitude. Vasoconstriction of the cutaneous vessels induced by increased NE secretion during hypoxia may obviously produce a fall in tcpO2. In view of the demonstrated correlation between increased catecholamine (NE) secretion and the various parameters for monitoring fetal intrapartum conditions, fetal hypoxic shock can be taken to be present if: wide and deep decelerations with an increased dip area occur in combination with tachycardia, severe fetal metabolic acidosis is present, tcpO2 is lowered to a few mm Hg (excluding artifacts).