Longitudinal determination of cerebral blood flow velocity in neonates with the Doppler technique

Using the Doppler technique, we followed the postnatal changes of the cerebral blood flow velocity longitudinally. Pulsatility index (PI) was measured in 91 neonates. In 26 normal term infants who were supine, PIs were initially raised (PI = 0.91 +/- 0.10), gradually falling over the first 12 hours after birth and remaining stable thereafter (PI = 0.78 +/- 0.05). PIs tended to be lower in neonates born by caesarean section but remained grossly within the normal range. Low birthweight infants showed high PIs during the first 12 hours after birth. Infants with a prone position showed a narrow standard deviation in PI soon after birth. There was a negative correlation between PI and the conceptional age and the coefficient of the correlation was 0.97156. The stage of active sleep, especially the REM period, was found to be an important factor which decreased the PI. We concluded that neonatal cerebral circulation significantly changes during the perinatal period and is affected by various physiological factors, especially sleep stages, the position of the infant and the conceptional age.