Noninvasive optical measures of CBV, StO₂, CBF index, and rCMRO₂ in human premature neonates' brains in the first six weeks of life

Abstract

With the causes of perinatal brain injuries still unclear and the probable role of hemodynamic instability in their etiology, bedside monitoring of neonatal cerebral hemodynamics with standard values as a function of age are needed. In this study, we combined quantitative frequency domain near infrared spectroscopy (FD-NIRS) measures of cerebral tissue oxygenation (StO 2 ) and cerebral blood volume (CBV) with diffusion correlation spectroscopy (DCS) measures of a cerebral blood flow index (CBF ix ) to test the validity of the CBV-CBF relationship in premature neonates and to estimate cerebral metabolic rate of oxygen (rCMRO 2 ) with or without the CBF ix measurement. We measured 11 premature neonates (28-34 weeks gestational age) without known neurological issues, once a week from one to six weeks of age. In nine patients, cerebral blood velocities from the middle cerebral artery were collected by transcranial Doppler (TCD) and compared with DCS values. Results show a steady decrease in StO 2 during the first six weeks of life while CBV remains stable, and a steady increase in CBF ix . rCMRO 2 estimated from FD-NIRS remains constant but shows wide interindividual variability. rCMRO 2 calculated from FD-NIRS and DCS combined increased by 40% during the first six weeks of life with reduced interindividual variability. TCD and DCS values are positively correlated. In conclusion, FD-NIRS combined with DCS offers a safe and quantitative bedside method to assess CBV, StO 2 , CBF, and rCMRO 2 in the premature brain, facilitating individual follow-up and comparison among patients. A stable CBV-CBF relationship may not be valid for premature neonates.

Difference in Cerebral and Peripheral Hemodynamics among Term and Preterm Infants during the First Three Days of Life

“…It has been reported that CBV increases with postconceptional age and that the relationship between these variables can be explained by the results of anatomical studies of cerebral blood vessels [15,20]. These previous reports support the current findings, as the mean GAs of infants from the studies which showed relatively low CBVs (1.7-1.97 ml/100 g) [9,19] were shorter than those from studies which showed relatively high CBVs (2.31-2.45 ml/100 g) [15]. The reason for the higher CBV values obtained by continuous wave NIRS than those obtained in this study is unclear, even taking into account the immaturities of the preterm infants (mean GA, 29 weeks) [4,8].…”

“…The study showed that the CBV in term infants was significantly higher than that in preterm infants during the first 3 days of life. There have been several studies on CBV in neonates measured by NIRS [4,8,9,15,19]. The CBVs of infants obtained using NIRS in these previous studies are summarized in table 2.…”

Noninvasive optical evaluation of spontaneous low frequency oscillations in cerebral hemodynamics

“…DCS is a relatively new technique which can directly probe blood flow in deep tissues including the cerebral cortex (Cheung et al, 2001;Culver et al, 2005;Dietsche et al, 2007;Durduran et al, 2009Durduran et al, , 2010Edlow et al, 2010;Gagnon et al, 2008;Li et al, 2008;Shang et al, 2011a,b;Zirak et al, 2010). Blood flow variations measured by DCS have been validated in various organs and tissues against other standards, including Doppler ultrasound (Roche-Labarbe et al, 2010), power Doppler ultrasound (Yu et al, 2005), laser Doppler (Durduran, 2004;Shang et al, 2011a), Xenon-CT , fluorescent microsphere measurement , and perfusion MRI (Yu et al, 2007). The hybrid NIR optical instrument offers direct and simultaneous measurements of CBF and cerebral oxygenation in microvasculature within the same region of cerebral cortex, which may bring new and informative insights about LFOs in local brain tissues.…”

Diffuse Optical Spectroscopy Measurement Of Cerebral Hemodynamics And Oxygen Metabolism During Anesthesia-Induced Burst Suppression In Rats

“…Cortical blood flow was measured with a home-built diffuse correlation spectroscopy (DCS) system employing a solid-state long coherence length laser at 785 nm for illumination and four photon-counting avalanche photodiodes for detection, as previously described [8]. The intensity auto-correlation function of each channel is computed by a digital correlator and the cerebral blood flow index (CBF i ) is determined by fitting the measured electric field autocorrelation functions to a model of dynamic light scattering in deep tissues.…”

“…Cortical blood flow was measured with a home-built diffuse correlation spectroscopy (DCS) system employing a solid-state long coherence length laser at 785 nm for illumination and four photon-counting avalanche photodiodes for detection, as previously described [8]. The intensity auto-correlation function of each channel is computed by a digital correlator and the cerebral blood flow index (CBF i ) is determined by fitting the measured electric field autocorrelation functions to a model of dynamic light scattering in deep tissues.The cerebral metabolic rate of oxygen index (CMRO 2i ) was estimated as previously described [8]. For these experiments, an assumption of baseline total hemoglobin concentration of 100 M at 60% oxygen saturation was used to convert the changes in hemoglobin concentrations measured by the CW into estimated absolute concentrations required for calculating the OEF.…”