Levels of catecholamines, arginine vasopressin and atrial natriuretic peptide in hypotensive extremely low birth weight infants in the first 24 hours after birth

Background: Extremely low birth weight infants (ELBWI) often suffer from severe hypotension in the early neonatal period. However, few previous studies have ever revealed plasma levels of vasoactive substances which regulate the cardiovascular system in ELBWI. Objective: To study plasma levels of vasoactive substances in ELBWI with hypotension during the first 24 h of life. Methods: 22 ELBWI with hypotension (gestational age 26.4 ± 1.9 weeks; birth weight 751 ± 135 g) were involved in the study. After initial volume therapy, the infants were arbitrarily divided into two groups depending on requirement of dopamine dosage: severe hypotension group (SH; dopamine >10 μg/kg/min, n = 9) and mild hypotension group (MH; dopamine ≤10 μg/kg/min, n = 13). Plasma levels of dopamine, norepinephrine, epinephrine, arginine vasopressin, and atrial natriuretic peptide were measured at admission and at 24 h after birth. Results: Infants in the SH group had higher plasma dopamine than infants in the MH group both at admission (median; range: 14,410; 224–46,770 vs. 7,900; 32–21,220 pg/ml, p < 0.05) and at 24 h (80,920; 494–146,100 vs. 25,680; 10,130–63,180 pg/ml; p < 0.05). The norepinephrine/dopamine ratio (median; range) was lower in the SH group than in the MH group at admission (0.3; 0.0–1.0 vs. 1.1; 0.1–25.1; p < 0.01). Plasma levels of atrial natriuretic peptide or arginine vasopressin were not different between the two groups. Conclusions: ELBWI with SH may have decreased conversion of dopamine to norepinephrine. We speculate that this mechanism may contribute to development of SH in ELBWI.