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) incombination with diffuse correlation spectroscopy (DCS) to quantitatively measure cerebral blood flow (CBF) and oxygenmetabolism (CMRO2) right at the infant’s bedside. We have previously found CBF and CMRO2are more sensitive indicatorsof cerebral pathophysiology than hemoglobin saturation (SO2). Using FDNIRS-DCS, we had found extremely prematureinfants 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 andhematocrit levels, affect evoked hemodynamic responses. The study protocol was reviewed and approved by theInstitutional Review Board for Partners Healthcare. We enrolled eleven premature infants in the neonatal intensive careunit at Brigham and Women’s Hospital. Three of them had Grade I GMH diagnosed by head ultrasound on the first threedays of life. We integrated continuous wave NIRS (CWNIRS) with DCS to measure dynamic changes of cerebral hemoglobinconcentrations (HbO) and CBF in response to somatosensory stimuli. For each measurement, we measured differentialpath length factors and baseline cerebral hemoglobin concentrations with FDNIRS to quantify relative hemodynamic andmetabolic changes (rHbO, rCBF and rCMRO2) in response to tactile stimulation. We observed a faster response time toreach peak value in preterm infants with increasing postmenstrual age (PMA), demonstrating the response matures withage to become more adult-like (r=-0.513, p=0.007). In addition, infants measured at older PMA tend to have responseswith a larger undershoot in HbO. However, the HbO undershoot did not translate into an undershoot in CMRO2. The HbOundershoot may therefore be a consequence of low hematocrit during the first two months of life which results ininsufficient oxygen supply and leads to abnormally large oxygen extraction from the blood. We found the activationpattern of Grade I GMH infants did not differ from premature infants without hemorrhage. The study is ongoing and showsour method is suitable to measure cerebral maturation in neonates with hemorrhage.

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