1621 NONINVASIVE NEONATAL REGIONAL CEREBRAL BLOOD FLOW

Abstract

Alterations in CBF are believed to be causally related to hypoxic-ischemic encephalopathy and intracranial hemorrhage in newborn infants. Using a modification of the standard 133-Xenon inhalation technique, rCBF was measured in 10 neurologically normal low birth weight (LBW)infants of mean birth weight 1322 g, gestational age 31.2 wks. The infants were studied at mean postnatal age 4.4 wks and had mean systolic BP 70, hgb 12.2g. 133-Xenon was administered as a small bolus (0.5 mCi/kg). Arterial Xenon concentration was measured with an external chest probe and used to correct for recirculation. Fifteen min. desaturation curves were obtained from 4 homologous cerebral regions and analyzed with Obrist's program. Compared to normal adults, mean grey matter flow (89.8 ml/100 gm/min) was significantly higher (p<.01) and mean grey matter weight (28.6%) significantly lower (p<.001). The interregional variation showed a trend towards low frontal and high occipital flows which is the opposite of adult regional flow patterns. There was a highly significant (p<.001) inverse correlation between CBF and hgb concentration. Unlike previous reports in the literature, the correlation between CBF and systolic BP was not significant, and the slope of the least squares regression line was not significantly different from zero. Our results demonstrate that noninvasive neonatal rCBF studies are possible and suggest that normal LBW babies have intact CBF autoregulation and physiologic responses to alterations in hgb concentration.

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