Nabij-infrarood spectroscopie op de neonatale intensieve zorgafdeling: kan het de behandeling beïnvloeden?
I. Introduction and background
In this proposal for PhD project we present clinical studies in different patient groups to assess cerebral oxygenation as measured with near-infrared spectroscopy (NIRS). Near-infrared spectroscopy has evolved from a purely research instrument to a monitor that is increasingly introduced into the clinical environment and especially in the neonatal intensive care unit. It has mainly been used for the measurement of the cerebral oxygenation and circulation and it increasingly becomes a monitor that helps the clinician in understanding the effect of different pathologies and treatments on the cerebral oxygenation. Our research team headed by Prof. Dr. Gunnar Naulaers has extensive experience in NIRS measurements in newborns. Cooperation with the Utrecht group headed by Prof. Dr. Frank Van Bel contributes in clinical insight and possibilities of this monitor since 5 years. A long existing cooperation (since 1999) with Prof. Dr. Ir. Sabine Van Huffel, ESAT/SCD & IBBT, Future Health department, Dept. of Electrical Engineering, Katholieke Universiteit Leuven, leaded to advanced signal analysis of NIRS parameters.
NIRS in the neonatology department
Near Infrared Spectroscopy was introduced by Jöbsis in 1977 as a safe and non-invasive technique to monitor cerebral oxygenation and hemodynamics in humans (1). The use in neonates to measure cerebral oxygenation was first reported by Brazy (2). Since then near-infrared spectroscopy started to become more popular for research in neonates, however it remained a difficult task to acquire stable measurements.
It was the introduction of spatially resolved spectroscopy by Matcher (3) that made it possible to measure absolute values of cerebral oxygenation. Because this method is less movement-sensitive, easier to use and reporting absolute values it leaded to commercial monitors that are increasingly used in cardiac surgery and also in neonatal intensive care units.
rScO2 and TOI
Regional cerebral oxygen saturation (rScO2) or Tissue Oxygenation Index (TOI) can be determined using spacially resolved spectroscopy and reflects the regional tissue oxygenation which is determined by the oxygen saturation in the venous (70-80%), capillary (5%) and arterial (20-25%) blood.
Reference values for newborns in the first days of life are reported and possible pittfalls are described. (4, 5).
Cerebral fractional tissue oxygen extraction or cFTOE is calculated from the rScO2 and pulse oximetry-measured arterial saturation (SaO2). It reflects the amount of oxygen extracted by brain tissue form the vascular pool compartment and thus the balance between cerebral oxygen delivery and the cerebral oxygen consumption (6).
Autoregulation can be measured by looking at the correlation between the NIRS monitored cerebral oxygenation and the blood pressure(7). Static cerebral autoregulation refers to the relation between cerebral blood flow (CBF) and mean arterial blood pressure (MABP) in a long time interval, while dynamic cerebral autoregulation refers to how the autoregulative mechanism behaves during the first 10 seconds after a change in MABP is presented (8). At the moment this work is in collaboration with the group of Professor Van Huffel. Impaired autoregulation can lead to increased or decreased CBF which has been known as a risk factor for intraventricular hemorrhage (IVH) and periventricular leucomalacia (PVL) (9).
II. General hypothesis and specific aims of the project
We will focus on three frequent clinical conditions in neonatology where measurement and analysis of NIRS monitored cerebral oxygenation patterns can make a difference in treatment decisions in the future neonatology department. Specific hypotheses and research questions of the different clinical conditions will be presented in each relevant chapter.