Abstract TP400: Evoked Functional Cerebral Hemodynamic and Metabolic Responses in Premature Infants with and without Germinal Matrix Hemorrhage

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We have created an innovative new method which uses frequency domain near-infrared spectroscopy (FDNIRS) in

combination with diffuse correlation spectroscopy (DCS) to quantitatively measure cerebral blood flow (CBF) and oxygen

metabolism (CMRO2) right at the infant’s bedside. We have previously found CBF and CMRO2are more sensitive indicators

of cerebral pathophysiology than hemoglobin saturation (SO2). Using FDNIRS-DCS, we had found extremely premature

infants with germinal matrix hemorrhage (GMH) have lower cerebral blood flow (CBF) and oxygen metabolism

(CMRO2) than gestational age-matched controls. For this study, we investigate whether GMH, along with age and

hematocrit levels, affect evoked hemodynamic responses. The study protocol was reviewed and approved by the

Institutional Review Board for Partners Healthcare. We enrolled eleven premature infants in the neonatal intensive care

unit at Brigham and Women’s Hospital. Three of them had Grade I GMH diagnosed by head ultrasound on the first three

days of life. We integrated continuous wave NIRS (CWNIRS) with DCS to measure dynamic changes of cerebral hemoglobin

concentrations (HbO) and CBF in response to somatosensory stimuli. For each measurement, we measured differential

path length factors and baseline cerebral hemoglobin concentrations with FDNIRS to quantify relative hemodynamic and

metabolic changes (rHbO, rCBF and rCMRO2) in response to tactile stimulation. We observed a faster response time to

reach peak value in preterm infants with increasing postmenstrual age (PMA), demonstrating the response matures with

age to become more adult-like (r=-0.513, p=0.007). In addition, infants measured at older PMA tend to have responses

with a larger undershoot in HbO. However, the HbO undershoot did not translate into an undershoot in CMRO2. The HbO

undershoot may therefore be a consequence of low hematocrit during the first two months of life which results in

insufficient oxygen supply and leads to abnormally large oxygen extraction from the blood. We found the activation

pattern of Grade I GMH infants did not differ from premature infants without hemorrhage. The study is ongoing and shows

our method is suitable to measure cerebral maturation in neonates with hemorrhage.

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