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Background: Conventional parameters of circulation that are routinely used in neonatal intensive care units, including blood pressure, have been reported to be inadequate in improving prognosis of very-low-birth-weight (VLBW) infants. Recently, the importance of evaluating the blood flow to each organ, including both vital and nonvital organs, has been increasingly recognized. Objectives: To study the changes in peripheral perfusion occurring in VLBW infants of less than 32 weeks’ gestation during the extrauterine transitional period. Methods: In 32 VLBW infants of less than 32 weeks’ gestation, forehead blood flow (FBF) and lower-limb blood flow (LBF) were measured for 48 h after birth using a novel laser Doppler flowmeter, and the indices of vascular resistance were estimated. Superior vena cava (SVC) blood flow was measured by echocardiography. Changes in these variables of circulation as well as the correlations were evaluated. Results: Both FBF and LBF significantly increased at 24 h, while the SVC flow remained unchanged over the same period. Both forehead and lower-limb vascular resistance indices significantly decreased at 24 h. LBF was negatively and positively correlated with estimated upper body vascular resistance and SVC flow, respectively. Conclusions: The increase in the peripheral blood flow along with the decrease in the peripheral vascular resistance indices, without an increase in the systemic blood flow at 24 h of age, indicated vasodilation in skin and subcutaneous tissue during the transitional period in VLBW infants. FBF and LBF can be useful parameters as indicators of both peripheral and systemic circulation.

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.