Free and sulfoconjugated plasma catecholamines in premature infants and mature newborn infants after birth

: Sulfate conjugation represents a major pathway for the inactivation of free catecholamines. We investigated the ability of newborns to protect the body against an overflow of free catecholamines by sulfoconjugation. No difference of free catecholamines in the umbilical artery was found in preterm and term newborns. Furthermore, preterm and term newborns were able to form sulfoconjugated catecholamines. In term newborns, but not in preterm newborns, there was a significant relationship between free catecholamines and their respective sulfoconjugated forms (p less than 0.001). In comparison to term infants sulfoconjugated dopamine and norepinephrine were significantly decreased in preterm newborns, although the placental extraction rates of these catecholamines were markedly lower in preterm infants. This favors the conclusion, that synthesis rather than increased degradation may be responsible for the low levels of sulfoconjugated catecholamines in preterm infants. Thus, preterm newborns might be less able to inactivate free catecholamines by sulfoconjugation. The clinical importance of these results concerning treatment of preterm newborns with dopamine and noradrenaline has yet to be established.