Infants born at an extremely low gestational age (\<29 weeks GA) (ELGA) are at risk for developing any grade of intraventricular hemorrhage (IVH). In association with IVH, ELGA infants may develop associated neuropathology including periventricular hemorrhagic infarction, post-hemorrhagic hydrocephalus and periventricular leukomalacia. Long-term neurodevelopmental outcomes depend on the severity of the hemorrhage. High-grade IVH (grade III or IV) is associated with a 50% risk for cerebral palsy and significant intellectual disability. Such disabilities have devastating and lifelong impact on affected children, the children's families and society. In more than 90% of the cases, IVH in ELGA infants occurs during the first three postnatal days. The major risk factor for IVH is the gestational age of the infant with greater immaturity being associated with the highest risk. The degree of prematurity of the infant relates to the immaturity of the vascular bed within the germinal matrix as well as challenges in the regulation of the cerebrovascular circulation. Specifically, increases, decreases and significant fluctuations in cerebral blood flow (CBF) have been shown to play important pathogenic roles in IVH. These CBF instabilities have been related to the mechanics of ventilation as well as to the severity of the infant's illness, with contributing factors of hypercarbia, hypovolemia, hypotension, restlessness, patent ductus arteriosus, and relatively high inspired oxygen concentrations. Another major contributing factor to CBF instabilities is the pressure-passive cerebral circulatory state in the unstable ELGA infants. To prevent such deleterious consequences on the developing brain of preterm infants, optimal therapeutic strategies that maintain both cardiopulmonary function and cerebrovascular stability need to be developed. The major obstacle impeding effective brain-oriented neonatal intensive care is the lack of a relevant bedside continuous monitor of cerebral blood flow.
Near-infrared spectroscopy (NIRS) is a non-invasive, non-ionizing method for monitoring and imaging of brain hemodynamics. Commercially available, FDA-approved NIRS systems provide hemoglobin concentration changes and relative hemoglobin oxygen saturation (rSO2) as a surrogate for cerebral perfusion and oxygen consumption. However currently there are no commercially available monitors, which can directly assess cerebral perfusion and oxygen consumption in preterm infants. The researchers are investigating the possibility of using a novel NIRS optical method to quantify cerebral perfusion, continuously, at the bedside in the NICU preterm population. The researchers believe the use of Diffuse Correlation Spectroscopy (DCS) as a stand-alone and in combination with frequency-domain (FD) or continuous wave (CW) NIRS will offer more robust diagnostic capabilities by directly quantifying cerebral blood flow (CBF), and cerebral oxygen metabolism (CMRO2). The researcher's preliminary efforts in animals and humans with this optical device show the potential of the technique.
Measurement Protocol Summary:
1. Start measurements within 48 hours of life, monitor for up to 72 hrs.
2. Up to 2 optical sensors will be attached with hydrogel, and affixed using either an infant hat headband or medical grade tapes.
3. Attached optical sensors will be adjusted every few hours to ensure that there is no disruption to skin integrity. Skin integrity will be assessed every time the optical sensors are moved and discussed with research nurse or nurse caring for infant
4. When available physiological parameters including heart rate, blood pressure, transcutaneous CO2 (TcCO2), cerebral oximetry and other systemic parameters from the bedside monitors will be collected to be compared to the optical data.
5. A research pulse oximeter will be attached to the baby to record arterial saturation (SpO2).
6. A small accelerometer will be attached to the optical sensor next to the optical sensor to record baby head motion.
7. In a subgroup of babies the researchers will also monitor enrolled infants with aEEG and FDNIRS. The aEEG leads are currently used in NICU for clinical care and the FDNIRS handheld probe is currently used in research. Depending on availability of the FDNIRS device and access to the infant, every 4 to 12 hrs, the researchers will perform FDNIRS measurements by using a hand-held optical sensor.
