Blood redistribution in the fetal brain during chronic hypoxia

Abstract

Background Studies on blood flow velocity in the fetal middle cerebral artery have revealed signs of brain sparing in chronic hypoxia. These signs of brain sparing can disappear in the terminal case, but whether this applies to the whole brain or only parts of it is unknown.Methods Velocity waveforms of the middle cerebral, anterior cerebral and posterior cerebral arteries were recorded in 221 pregnancies complicated by pregnancy-induced hypertension. The presence of brain sparing (pulsatility index < 2 standard deviations) was noted and correlated to outcome of pregnancy, including emergency operative intervention and/or neonatal distress. ResultsSigns of brain sparing in the anterior cerebral artery were found in 90 fetuses, and in the middle cerebral and posterior cerebral arteries in 52 and 65, respectively. Signs of brain sparing in the anterior cerebral artery showed the strongest relationship to adverse perinatal outcome. The anterior cerebral artery was the only vessel in which signs of brain sparing were predictive of perinatal mortality.Conclusions Velocimetry of the anterior cerebral artery appears to be superior to that of the middle cerebral and posterior cerebral arteries as a means to predict adverse perinatal outcome. Anterior cerebral artery brain sparing may therefore be less transitory than sparing in the middle cerebral and posterior cerebral arteries, possibly suggesting that the frontal lobes are spared longer than the lateral and occipital regions of the fetal brain.

Impact of chronic hypoxemia on blood flow to the brain, heart, and adrenal gland in the late-gestation IUGR sheep fetus

“…Ultrasound studies in human fetuses suggest that a redistribution of blood flow toward the brain occurs as a fetal adaptation to chronic hypoxemia (19,76). In chronically hypoxemic fetuses, there is also evidence of increased blood flow velocity in the anterior, middle, and posterior cerebral arteries, although only blood flow velocity in the anterior cerebral artery was related to perinatal outcome (21). Interestingly, ultrasound studies in humans suggest that twice as many fetuses may have sparing of adrenal growth (based on increased velocity of adrenal blood flow) compared with a sparing of brain growth (20).…”

Chronic hypoxia increases peroxynitrite, MMP9 expression, and collagen accumulation in fetal guinea pig hearts

“…Maternal hypoxia caused fetal growth restriction, a compensatory increase in placental growth, and pups that exhibited fetal heart-and brain-sparing effects (33,34). We previously reported that maternal hypoxia increases red blood cell content and reticulocyte number in fetal guinea pig blood (2) and induces local tissue hypoxia of fetal hearts as evidenced by increased hypoxia-inducible factor-1α mRNA and protein levels in HPX fetal guinea pig cardiac ventricles (1).…”

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

“…There is evidence that during chronic hypoxia, a BSF in the ACA is more frequent, less transitory, and better indicates adverse perinatal outcomes than BSF in the middle or posterior cerebral arteries 7 . Dubiel et al 7 speculate that during chronic hypoxia the cerebral regions nourished from the ACA is spared longer than regions nourished from other cerebral arteries. No study has yet addressed this issue during acute hypoxic stress.…”