Cerebral Blood Flow in Preterm Infants during the First Week of Life

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Abstract
Forty-two preterm infants of 28–33 weeks of gestation were studied once during the first week of life by 133-Xenon clearance after intravenous injection to estimate global cerebral blood flow. Count rates detected over the chest were corrected for chest wall contribution and used as arterial input function. A neonatal blood-brain partition coefficient of Xenon was used for the calculation of a mean flow estimator (CBF-∞). The techique was internally validated by use of differently obtained arterial input functions. In 11 infants wihout respiratory distress, CBF-∞ was 19.8 ml/100 g/min ±5.3 SD. In 24 infants treated with mechanical ventilation CBF-∞ was 11.8 ml/100 g/min ±3.2 SD. In 7 infants treated with continous positive airway pressure CBF-∞ was 21.3 ml/100 g/min ±12.0 SD. When the reduction of CBF-∞ associated with mechanical ventilation was taken into account, the 9 infants with subependymal/intraventricular haemorrhage had increased CBF-∞. The effects of gestational age, birthweight, mode of delivery, postnatal age, mean arterial blood pressure, PaCO2, blood haemoglobin and phenobarbitone medication were also analysed and found inconsistent. In conclusion, CBF was lower than expected and in infants requring mechanical ventilation the values were lower still.