The aim of the study was to evaluate BNP in preterm infants < 28 weeks on the second day of life, when it is still unknown, if a patent ductus arteriosus is hemodynamic significant or not. We hypothesized that high plasma BNP concentrations on day 2 are associated with the need of PDA intervention in the further course.

From the study infants blood samples (0.1ml) were collected in K-EDTA microtubes within 24 to 48 hours of age through umbilical artery catheter aspiration or routine venous puncture. The samples were spun at 7000 rpm for 3 minutes. Platelet-free plasma was stored at -20°C until BNP analysis of all collected samples was carried out. The BNP assay was performed using a fully automated immunoassay system ADVIA method for the Centaur System (Bayer Diagnostic Division).

In preterm infants who were treated with indomethacin or surgical ligation we collected additional blood samples 2-4 hours before intervention and 24 hours after the completion of the ductus treatment.

Inclusion Criteria:

• Written parental informed consent
• Preterm infant < 28 weeks of gestation
• Admitted to our NICU within 48 hours after birth

Exclusion Criteria:

• No written parental informed consent,
• Congenital heart disease,
• Death