Ball R H, Parer J T, Caldwell L E, Johnson J
Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco.
Am J Obstet Gynecol. 1994 Dec;171(6):1549-55. doi: 10.1016/0002-9378(94)90400-6.
Our purpose was to compare the ovine fetal response to severe, damaging asphyxia resulting from umbilical cord occlusion with that seen in uterine artery occlusion.
Six ovine fetuses were exposed to severe asphyxia produced by partial umbilical cord occlusion for 90 minutes. Fetal blood pressure and heart rate, blood gases, acid base status, electrocorticogram, and electromyogram were recorded. Regional blood flow (radioactive microspheres) measurements were performed at control and 30, 60, and 90 minutes of occlusion and 30 minutes after release.
During the period of occlusion pH fell from 7.37 +/- 0.01 (mean +/- SEM) to 6.82 +/- 0.03 at 90 minutes, base excess from 5 +/- 1 to -22 +/- 2 mEq.L-1 and oxygen content from 3.3 +/- 0.4 mmol.L-1 to a nadir of 1.6 +/- 0.4 mmol.L-1 (p < 0.05). There was no significant long-term change in fetal heart rate or blood pressures. The fetal electrocorticogram was profoundly suppressed during asphyxia, and seizure activity was documented after release of occlusion in all surviving animals. Umbilical blood flow fell to 21% +/- 5% of control by 60 minutes of occlusion and remained depressed until release. Brain and adrenal blood flows increased during asphyxia. Heart and intestinal blood flows did not change significantly from control values. Combined ventricular output and spleen, kidney, and carcass blood flow fell during the insult. Oxygen uptake by the cerebral cortex remained stable during occlusion. Oxygen uptake by the lower carcass fell to 15% +/- 7% of control.
Umbilical cord occlusion produces similar levels of asphyxia and evidence of encephalopathy (seizures), compared with previous experiments with uterine artery occlusion. The fetal response with respect to blood flow redistribution and organ oxygen uptake, however, differs. These differences may signify that with uterine artery occlusion the brain may be more vulnerable, whereas with umbilical cord occlusion the heart may be at greater risk.
我们的目的是比较羊胎儿对脐带闭塞导致的严重、损伤性窒息的反应与子宫动脉闭塞时的反应。
六只羊胎儿暴露于部分脐带闭塞产生的严重窒息状态90分钟。记录胎儿血压、心率、血气、酸碱状态、脑电图和肌电图。在对照时、闭塞30、60和90分钟时以及解除闭塞30分钟后进行区域血流（放射性微球）测量。
在闭塞期间，pH值从7.37±0.01（均值±标准误）在90分钟时降至6.82±0.03，碱剩余从5±1降至-22±2 mEq.L-1，氧含量从3.3±0.4 mmol.L-1降至最低点1.6±0.4 mmol.L-1（p<0.05）。胎儿心率或血压没有显著的长期变化。窒息期间胎儿脑电图受到严重抑制，所有存活动物在解除闭塞后均记录到癫痫活动。到闭塞60分钟时，脐血流量降至对照值的21%±5%，并一直保持低水平直至解除闭塞。窒息期间脑和肾上腺血流量增加。心脏和肠道血流量与对照值相比没有显著变化。在损伤期间，心室联合输出量以及脾脏、肾脏和躯体血流量下降。闭塞期间大脑皮层的氧摄取保持稳定。下躯体的氧摄取降至对照值的15%±7%。
与先前子宫动脉闭塞的实验相比，脐带闭塞产生了相似程度的窒息和脑病证据（癫痫）。然而，胎儿在血流重新分布和器官氧摄取方面的反应有所不同。这些差异可能表明，子宫动脉闭塞时大脑可能更易受损，而脐带闭塞时心脏可能面临更大风险。
