Near infrared spectroscopy in assessing patent ductus arteriosus in preterm infants in the first week of life

A patent ductus arteriosis (PDA) with left-right shunting is a common problem
in preterm infants weighing <1500 gram. A PDA is associated with high
morbidity and mortality. This is due to the diastolic steal to organs and the
increased pulmonary flow. Described morbidities include prolonged requirement
for ventilatory support, bronchopulmonary dysplasia , respiratory distress,
pulmonary hemorrhage, increased risk of infections, cerebral haemorrhage,
renal hypoperfusion, necrotizing enterocolitis and heart failure. Early
closure of PDA decreases the risk of morbidities.

Treatment modalities include cyclo-oxygenase inhibitors and surgical ligation.
Evidence lacks defining parameters for starting treatment. To tackle this last
problem, assessing the magnitude of the ductus arteriosus can be helpful. It is
thus important to easily and accurately determine the left-right shunt
fraction.

The present diagnostic tool to assess the patency of the ductus arteriosus is
echocardiography. Echocardiography can differentiate between a patent versus a
closed ductus arteriosus, but does not quantify the shunt fraction. Performing
echocardiography and interpreting its results require specific expertise. The
diagnosis of PDA is therefore dependent on the availability of this experts
(pediatric cardiologist). Therefore, other easier and non-invasive method for
diagnosing PDA is needed.

Spatially resolved near infrared spectroscopy (NIRS) measures tissue
oxygenation saturation based on assessment of oxygenated and deoxygenated
haemoglobin by comparing scattered and absorbed near infrared light. Initially
it has been used to assess cerebral oxygenation and haemodynamics, but recently
it has been suggested to be useful in detecting a patent ductus arteriosus as
well. In case of an haemodynamically significant PDA with left-right shunting,
NIRS can detect an increased pulmonary tissue oxygen saturation, reduced
peripheral tissue oxygen saturation in post-ductal region and a reduced
cerebral oxygen saturation.

This study will investigate whether NIRS can be used as a diagnostic tool in
determining if a ductus arteriosus is still open or not.

Primary Objective:
To investigate whether spatially resolved NIRS can differentiate between a
patent or closed ductus arteriosus.

Observational cohort study. The study will be carried out in the department of
neoatology of Radboud University Nijmegen Medical Centre. Preterm infants born
with a gestational age <32 weeks with a patent ductus arteriosus (confirmed by
echocardiography) within the first week of life, which needs to be
pharmacologically or surgical closed, will be included.
Tissue oxygen saturations will be measured before and after treatment is given.
The tissue oxygen saturation will be measured using spatially resolved NIRS
(INVOS oximeter,Somanetics). The tissues to be measured are pre-ductally the
right arm and the chest (lungs), post-ductally the thigh muscle and the frontal
head (brain).

A comparison will be made between the echocardiographic findings and:
- Absolute tissue oxygen saturation in pre-and post-ductal areas
- Difference between tissue oxygenation saturation in pre- and post-ductal areas
- Ratio between tissue oxygen saturations in pre- and post- ductal areas

Echocardiographic findings:
- Ductal diameter
- Left atrium/Aorta ratio
- Diastolic flow
- Shunt direction
- Left ventricular systolic dimension (LVDs)
- Left ventricular diastolic dimension (LVDd)

NIRS is a non-invasive method. Near infrared light is harmless for tissue. The
us of NIRS is therefore without any risk for the preterm infants. At most the
application and the removal of the NIRS sensors might give a few dyscomfort.