SEVERE BIRTH ASPHYXIA AND ABNORMAL CEREBRAL BLOOD-FLOW VELOCITY

Thirty-four fullterm infants with postasphyxial encephalopathy (PAE) were studied with ultrasound to assess cerebral blood-flow velocity (CBFV). A control group of 126 healthy infants also had CBFV recordings during the first week of life. Measurements for the majority of the asphyxiated group fell into two abnormal patterns in relation to the control group: four had low CBFV (less than 2 SD below the mean) and 17 had high CBFV (greater than or equal to 2 SD above the mean); all had severe PAE. Median age at the first high measurement was 26 hours. There were no statistically significant differences between infants with normal and abnormal CBFV in measurements of PaCO2 or mean arterial blood-pressure. A Pourcelot Resistance Index (PRI) less than 0.55 was common in the presence of high CBFV, but never seen with low measurements. 21 of the 34 infants died of their asphyxial insult and four of the survivors have severe cerebral palsy at a median age of two years. Three of the four with low CBFV died, and no infant with CBFV greater than 3 SD survived without severe impairment. The positive predictive value of CBFV measurements less than 2 SD or greater than 3 SD for death or severe impairment is 94 per cent, compared with 83 per cent for low PRI alone. The authors believe that high CBFV is the result of vasoparalysis of cerebral arterioles and that it represents a form of irreversible cerebral injury.     

CEREBRAL BLOOD-FLOW VELOCITY DURING THE FIRST WEEK OF LIFE OF PRETERM INFANTS AND NEURODEVELOPMENT AT TWO YEARS

Disturbances in perinatal cerebral perfusion appear to be associated with unfavourable neurodevelopmental outcome. Using transcutaneous Doppler technique, the authors investigated cerebral blood-flow velocity patterns in the anterior cerebral artery (ACA) of an intensive care-unit population of preterm infants during the first week of life. The results were correlated with neurodevelopmental outcome at two years of age. Children with major disability at two years of age had significantly higher pulsatility index (PI) values, mainly increased peak systolic flow velocity (PSFV), compared with children with normal or more favourable outcome. End diastolic flow velocity and area under the velocity curve values of the ACA did not differ between the groups, indicating that cerebrovascular resistance and cerebral blood-flow were not different. It is thought that the higher PI and PSFV values were caused by increased compliance of the vascular bed supplied by the ACA, possibly induced by congestion and oedema of the periventricular white-matter due to ischaemic lesions, which also cause periventricular leukomalacia.     

EFFECTS OF EXTRACT OF GINKGO BILOBA ON INTRACRANIAL PRESSURE,CEREBRAL PERFUSION PRESSURE,AND CEREBRAL BLOOD FLOW IN A RAT MODEL OF SUBARACHNOID HAEMORRHAGE

The purpose of this study was to investigate in effect of extract of Ginkgo biloba (EGb) on cerebral blood perfusion in a subarachnoid haemorrhage (SAH) rat model. SAH lead to an increase in intracranial pressure and decrease in cranial perfusion pressure and regional cerebral blood flow in all groups. However, the intracranial pressure increases in EGb groups were less than that of the vehicle group (p < .01), whereas the reduction in cranial perfusion pressure and regional cerebral blood flow in the EGb group was less than that of the vehicle and SAH groups (p < .01). It was concluded that EGb attenuates the increase in intracranial pressure and reduction in cerebral blood perfusion after SAH.     

THE RISE TIME OF INTRACRANIAL ECHO PULSATIONS AND INTRACRANIAL PRESSURE

It would not appear that measurement of Rise Times of echo pulsations either in amplitude or in range will be useful in determining cases of raised intracranial pressure.