Intracerebral regional distribution of blood flow in response to uterine contractions in growth-restricted human fetuses

Objective: To explore middle cerebral artery (MCA) and anterior cerebral artery (ACA) blood flow responses to superimposed acute hypoxemia in growth -restricted fetuses with and without established brain-sparing flow during basal conditions. Material and methods: 47 term fetuses suspected of growth restriction were exposed to an oxytocin challenge test with simultaneous cardiotocography and Doppler velocimetry in the umbilical artery, MCA and ACA. The MCA-to-ACA pulsatility index (PI) ratio was calculated during basal conditions, contractions and relaxations. Basal brain-sparing flow was defined as an MCA-to-umbilical artery PI ratio of <1.08, de novo brain-sparing flow in the MCA as an MCA PI decrease with I standard deviation during uterine contractions or relaxations compared with basal measurements, and de novo brain-sparing flow in the ACA as an ACA PI decrease with l standard deviation. Non-parametric statistical tests were used with P<0.05 considered significant. Results: MCA and ACA PI were both significantly tower in the brain-sparing flow group (N=8) during basal conditions (P <= 0.01). During the oxytocin challenge test, MCA and ACA PI both decreased in the non-brain -sparing flow group (N=39) (P <= 0.02) but not in the brain -sparing flow group (P >= 0.4). The MCA-to-ACA PI ratio remained unchanged in both groups. de novo brain-sparing flow calculations revealed no preferential flow to any cerebral artery. Conclusion: Cerebral circulatory responses to acute hypoxemia are synchronized in the middle and anterior cerebral arteries without any preferential regional flow distribution. (C) 2007 Elsevier Ireland Ltd. All rights reserved.