Cerebral blood flow requirement for brain viability in newborn infants is lower than in adults

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Abstract
Measurements of regional cerebral blood flow (CBF) with positron emission tomography in adult humans with cerebrovascular disease have demonstrated consistently that values below 10 ml/(100 gm · min) occur only in infarcted brain. Although experimental data suggest that the newborn brain may be more resistant to ischemic injury than the adult brain, the minimum CBF necessary to sustain neuronal viability in newborn infants is unknown. We have measured CBF with positron emission tomography in 16 preterm and 14 term newborn infants and have determined the relationship between CBF and subsequent brain function as assessed by neurological examination and developmental assessment. The range of mean CBF in the preterm infants was 4.9 to 23 ml/(100 gm · min) and the range of mean CBF in the term infants was 9.0 to 73 ml/(100 gm · min). Five preterm infants and one term infant with mean CBF less than 10 ml/(100 gm · min) survived. Three of these 5 preterm infants, with mean CBF of 4.9, 5.2, and 9.3 ml/ (100 gm · min, respectively, have normal neurological examinations and Bayley Scales of 80 or greater at 6, 6, and 24 months of age, respectively. One (mean CBF 6.9) has normal cognitive development (Bayley 103) and a mild spastic diplegia at age 19 months, and one infant (mean CBF 6.2) has a left hemiparesis and a Binet IQ score of 70 at age 33 months. The term infant, with a mean CBF of 9.0 ml/(100 gm · min), was developing normally when he died of Septembersis at age 5 months. These data indicate that mean CBF as low as 5 ml/(100 gm · min) in newborn infants can be associated with normal subsequent neurological development and therefore with preservation of a substantial number of cortical/ neurons. Since the minimal CBF below this value necessary to maintain neuronal viability in newborn infants remains to be determined, measurements of CBF in the newborn period should not be used in determination of brain death.