Yaffe H, Parer J T, Block B S, Llanos A J
Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco 94143.
J Dev Physiol. 1987 Aug;9(4):325-36.
Pregnant sheep were chronically instrumented with fetal and maternal catheters and an inflatable occluder and electromagnetic flow transducer were placed on the uterine artery. Uterine blood flow was reduced for approximately 15 minutes to 25 percent, 50 percent, or 75 percent of control uterine blood flow. Fetal blood gases, arterial blood pressure, heart rate and regional distribution of blood flow (by radioactive microspheres) were measured. With progressive reduction of uterine blood flow there was an increasing degree of fetal asphyxia, as measured by blood gases and acid base state. At moderate degrees of asphyxia the fetus responded by redistribution of blood flow to certain organs, namely heart, brain, and adrenal gland, thus preserving oxygenation of these organs. During the most severe degree of asphyxia induced by reduction of uterine blood flow to 25 percent of control there is a reduction of fetal blood flow due to generalized vasoconstriction of essentially all organs. We hypothesize that this is due to the inability of the vasodilator mechanisms to sufficiently oppose the vasoconstrictor mechanisms. Also, because the oxygen consumption of the "vital" organs would be decreased this can be described as the stage of decompensation.
对怀孕母羊进行长期仪器植入，在胎儿和母体身上放置导管，并在子宫动脉上放置可充气封堵器和电磁流量传感器。子宫血流量减少至对照子宫血流量的约25%、50%或75%，持续约15分钟。测量胎儿血气、动脉血压、心率以及血流的区域分布（通过放射性微球）。随着子宫血流量的逐渐减少，通过血气和酸碱状态测量，胎儿窒息程度不断增加。在中度窒息时，胎儿通过将血流重新分配到某些器官，即心脏、大脑和肾上腺，从而维持这些器官的氧合。在将子宫血流量减少至对照的25%所导致的最严重窒息期间，由于基本上所有器官的全身性血管收缩，胎儿血流量减少。我们推测这是由于血管舒张机制无法充分对抗血管收缩机制。此外，由于“重要”器官的氧消耗量会降低，这可被描述为失代偿阶段。
