The purpose of this study is to examine the influence medical or surgical treatment for patent ductus arteriosus in preterm infants on cerebral and renal tissue oxygenation and on cardiac output.

In this observational trial the investigators want to examine whether clinical or echocardiographic parameters of patent ductus arteriosus are related to

• cerebral tissue oxygen saturation, total hemoglobin, fractional tissue oxygen extraction and HbD
• renal tissue oxygen saturation, total hemoglobin, fractional tissue oxygen extraction and HbD

as measured by near infrared spectroscopy

and to

• stroke volume
• cardiac output

as measured by electrical cardiometry.

The investigators want to examine the impact of surgical and medical treatment for patent ductus on these parameters. The investigators want to compare the change of these parameters between responders to medical treatment and nonresponders.

Inclusion Criteria:

• Newborn infant below 34 weeks postmenstrual age at the time of birth
• Patent ductus arteriosus with signs of hemodynamic relevance (as judged by the attending neonatologist)
• parental informed consent

Exclusion Criteria:

• Patent ductus arteriosus as part of malformation syndrome
• Additional major cardiovascular malformations

Preterm neonates with patent ductus arteriosus treated in our hospital