新生児脳内の近赤外領域拡散スペクトルの研究

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In order to prevent and manage hypoxic-ischemic encephalopathy in neonates, it is very important to determine the oxygenated state of Hb, oxygen saturation (SbO_2), the redox state of cytochrome c oxidase, and cerebral blood volume in the cerebral tissue correctly and at real time. Using continuous near infrared spectroscopy (cNIRS) with multi-point method, we converted both the flattened and nonlinear diffusion spectra to both the non flattened and linear spectra and normalized different light pathlengths between respective spectra. Upon calculation of molar ratios of individual chromophore components existing in the light path of a given biological material, it was feasible to determine oxyhemoglobin, deoxyhemoglobin, SbO_2, and the redox state of cytochrome c oxidase in the cerebral tissue in vivo.Comparing the results measured on the scalp with the result measured directly on the dura of the piglets, a close agreement was proven to exist between the results of indirect and direct measurements. We studied the oxygenation of hemoglobin and the redox state of cytochrome c oxidase in full term and premature infants. SbO_2 was 60-70% in normal term infants and 50-75% in premature infants. The asphyxiated infant had a significantly higher total Hb and SbO_2 than the normal neonates controls. In apneic spell, the oxidized form of cytochrome c oxidase decreased after SbO_2.Thus, this study demonstrates that continuous bedside monitoring of cerebral hemoglobin oxygenation and the redox state of cytochrome c oxidase might become a useful index for evaluating cerebral hemodynamics and energy state.