CEREBRAL OXYGENATION AND HEMODYNAMICS IN THE FETUS AND NEWBORN-INFANT

Quantitative techniques have been derived for the measurement of globa l cerebral blood flow, cerebral blood volume, its response to changing arterial carbon dioxide tension and mixed cerebral venous saturation in the human newborn undergoing intensive care. Normal ranges have bee n established and significant disturbances of cerebral oxygenation and perfusion have been demonstrated in a variety of pathological conditi ons. Recently, absolute cerebral deoxyhaemoglobin concentration has be en obtained in the newborn using second differential spectroscopy. Whe n combined with the measurement of total cerebral haemoglobin concentr ation, the mean saturation of cerebral blood (SmcO(2)) may be obtained , allowing global cerebral oxygenation to be determined continuously i n the intensive care unit. Marked changes in the concentrations of cer ebral oxy- and deoxyhaemoglobin have been observed in foetuses undergo ing labour. Measurements of SmcO(2) from the foetal brain prior to del ivery have shown the expected close correlation with acid-base status at birth. Although movement artefact remains a theoretical risk during uterine contractions, preliminary measurements of optical path length by intensity modulated spectroscopy have demonstrated only small fluc tuations. In future the clinical application of time, phase and spatia lly resolved spectroscopy is likely to improve both the quantitative a ccuracy and the regional specificity of physiological measurements in the foetal and neonatal brain.