Cerebral blood flow velocity and failure of autoregulation in neonates: their relation to outcome of birth asphyxia.

Using the continuous wave Doppler technique, we examined the pulsatility index (PI) of the anterior cerebral artery in 14 asphyxiated infants. We also measured the blood pressure (BP) and fontanel pressure (FP) and calculated the cerebral perfusion pressure (CPP). According to the neurological prognosis, we divided the 14 infants into two groups and studied correlation of each factor. In the good-prognosis group (n = 11), PIs are within normal limits. There is a negative correlation between BP, CPP and PI, suggesting that the autoregulation of cerebral blood flow has been lost. On the other hand, there is no significant correlation between BP, CPP and PI in the poor-prognosis group (n = 3). These infants are thought to have lost the autoregulation, but their cerebral blood flow is not pressure-passive. Not only BP but also brain edema, vasodilation, and possibly other factors may contribute to determine the cerebral blood flow. Concerning FP, no remarkable correlations are found between two groups. It is therefore very important to monitor the PI, BP, FP in asphyxiated infants even if the degree of asphyxia is mild.