REGIONAL RESPONSE TO HYPOXEMIA AND HYPERCAPNIA IN THE FETAL HUMAN BRAIN - DOPPLER STUDY OF DIFFERENT TRACTS OF THE MIDDLE CEREBRAL-ARTERY

Objective: To study the influence of fetal blood gas and pH on vascula r resistance of different tracts of the middle cerebral artery. Method s: Forty-three singleton pregnancies complicated by pregnancy-induced hypertension and intrauterine growth retardation were evaluated. All f etuses were submitted to Doppler study of both the proximal and the di stal tl act of the middle cerebral artery. Percutaneous umbilical vein blood sampling to assess fetal pO(2) pCO(2), and pH was performed bef ore delivery. Linear regression and one-way analysis of variance were used for statistical analysis. Results: Hypoxemia, hypercapnia, and ac idemia were found in all fetuses. pO(2) and pCO(2) were found to be re lated to velocimetric indices obtained from the proximal tract of the middle cerebral artery. No relation was found between blood gas tensio ns or pH and Doppler indices from the distal tract of the middle cereb ral artery. Postnatal periventricular leucomalacia associated with ele vated fetal cerebral Doppler indices was observed in two fetuses. More over, five cases of postnatal intraventricular hemorrhage associated w ith abnormal fetal cerebral Doppler velocimetry were found. Conclusion s: Our findings support the hypothesis that there is a hierarchy of re sponsivity between the deep and superficial brain areas. Serial Dopple r measurements of the proximal and the distal tracts of middle cerebra l artery blood flow could predict perinatal brain damage in hypoxic fe tuses.