Changes in fetal tissue blood flow under long-term hypoxemia

我们首先利用彩色微球技术测量胎儿组织中的血流，得到了类似于放射性微球方法的模式。因此，通过使用这种彩色微球方法，我们随后测量了低氧急性期胎羊模型的脑血流量。在低氧血症期间，中脑和髓质的血流量增加明显大于大脑皮层的血流量增加。随后，我们重点研究了新生儿窒息足月(0.85孕周)和早产儿(0.7孕周)之间低氧血流量分布的动态变化。在这一系列实验中，早产儿在低氧血症时的血流量增加几乎与近月儿相似。一个例外是，早产儿的海马区血流量比近期增加的更多。最后，我们研究了硫酸镁在低氧血症中对低氧血症反应的影响，因为镁在临床上是常用的。这项实验表明，与对照组相比，镁注射可以维持流向大脑皮层、心脏和肾上腺的血流量的低氧性增加。有趣的是，我们还观察到镁在低氧时不会减慢胎儿心率或升高血压。总之，可以用彩色微球法测量胎儿血流量。利用这一点，我们已经表明，在早产儿和服用镁的胎儿中，血流分布中的低氧变化基本保持不变。

We first utilized a colored microsphere technique to measure blood flow in fetal tissue, that resulted in similar patterns comparable to a radioactive microsphere method. Thus, by using this colored microsphere method, we subsequently measured the brain blood flow in fetal sheep models during an acute phase of hypoxemia.Blood flow increases in the midbrain and medulla were significantly lager than that of the cerebral cortex during hypoxemia. Subsequently, we focused on the developing changes in hypoxemic blood flow distribution between nea term (0.85 gestation) and preterm (0.7 gestation). In this series of experiments, blood flow increase during hypoxemia in the preterm fetuses was almost similar to that in the near term fetuses. One exception was that hippocampal blood flow was more increased in the preterm than in the near term. Finally, we studied the effects of magnesium sulfate on hypoxemic responses during hypoxemia, since magnesium were commonly used in clinical practice. This experiment showed that hypoxemic increase in blood flow to the cerebral cortex, heart, and adrenal were maintained under magnesium infusion, compared to its controls. Interestingly, we also observed that magnesium did not slow fetal heart rate or increase blood pressure during hypoxemia.In conclusion, fetal blood flow can be measured with the colored microsphere method. Using this, we have shown that hypoxemic changes in blood flow distribution is basically maintained in the preterm fetuses and in fetuses under magnesium administration.