Catecholamine Release in the Newborn Infant at Birth

Abstract

Summary: Catecholamines were determined by a fluorometric technique in umbilical blood which was collected from new born infants immediately alter birth. The mean catecholamine concentration was 62.1 nmol/liter in the umbilical artery and 29.3 nmol/liter in the umbilical vein of newborn full term infants delivered uneventfully. This value is considerably higher than in resting adults. Similar levels of catecholamines were seen alter elective cesarean sections, whereas considerably higher levels were found after breech deliveries. In the full term asphyxiated infants about a 4-fold increase of the catecholamine concentration was found in both the umbilical arterial and venous blood. The amine concentration level correlated inversely to the pH below 7.25 (¹⁰log catecholamine concentration versus pH, r = −0.71). Preterm infants had, in general, lower amine levels than full term infants both after uneventful deliveries and after intrauterine asphyxia. The catecholamine levels were considerably increased in the newborn infants who showed some kind of abnormal fetal heart rate variation during the last hour before birth; in particular baseline changes were associated with high levels whereas only a moderate increase was seen after loss of beat-to-beat variation.

Speculation: The high catecholamine concentrations in umbilical blood, seen even after uneventful deliveries, indicate that the sympathoadrenal system might have a functional role in the fetus at delivery. The enormous levels at asphyxia might be of importance to sustain the circulatory homeostasis.

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