Objective: Our purpose was to determine ovine fetal regional blood flow changes during asphyxia of such severity that it results in seizures.
Study design: Six ovine fetuses were exposed to severe asphyxia produced by maternal uterine artery occlusion for up to 90 minutes. Fetal blood pressure and heart rate, blood gases, acid base status, electrocorticogram, electromyogram and regional blood flow (radioactive microspheres) measurements were recorded.
Results: During the asphyxial insult pH fell from 7.39 +/- 0.01 (mean +/- SEM) to 6.99 +/- 0.01 at 60 minutes, base excess from 4 +/- 1 to -16 +/- 1 mEq/L, and oxygen content from 3.5 +/- 0.4 to 0.5 +/- 0.1 mmol/L (p < 0.05). There was no significant change in fetal heart rate or blood pressure. The fetal electrocorticogram was profoundly suppressed during asphyxia, and seizure activity began 50 +/- 19 minutes after the release of occlusion in all surviving animals. Blood flow increased to the heart and adrenals during asphyxia and decreased to spleen, gut, kidneys, and carcass (p < 0.05). There was no change in combined ventricular output and umbilical blood flow. There was no significant increase in total cerebral perfusion.
Conclusion: When the ovine fetus is exposed to asphyxia of sufficient severity to produce neurologic damage (seizures), the pattern of redistribution of blood flow is comparable to the response to lesser asphyxia, except that a significant increase in total brain blood flow does not occur. This finding may have an important association with the development of long-term neurologic damage.