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 (CMRO
2
) right at the infant’s bedside. We have previously found CBF and CMRO
2
are more sensitive indicators
of cerebral pathophysiology than hemoglobin saturation (SO
2
). Using FDNIRS-DCS, we had found extremely premature
infants with germinal matrix hemorrhage (GMH) have lower cerebral blood flow (CBF) and oxygen metabolism
(CMRO
2
)
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 rCMRO
2
) 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 CMRO
2
. 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.
Comparison of time-resolved and continuous-wave near-infrared techniques for measuring cerebral blood flow in piglets