pathophysiological study of fetal distress using chronic preparation in sheep

我们对妊娠110~130天的绵羊进行了手术。在进行颈总动脉插管，应用心脏电极，并安装脐带封堵器后，胎儿返回子宫完成妊娠期。连续监测胎心率、胎儿动脉压、脐动脉血流量、宫内压、母体动脉压。术后第5天，当血气值和FHR模式反映生理状态时，进行实验。实验采用一系列完全性脐带闭塞模型，分析胎儿和母体血气，并测定血浆去甲肾上腺素和肾上腺素。胎儿心率减速曲线下降段的斜率减小，并与胎儿动脉血pH、碳酸氢盐、对数血浆去甲肾上腺素和肾上腺素浓度密切相关。在反复脐带压迫期间，通过胎心率减速斜率来预测胎儿的酸碱和激素状态。当胎儿酸血症进展到动脉pH值约7.15时，在释放脐带压迫后立即观察到特征的超调加速。当胎儿动脉pH低至7.15时，脐带压迫所致的胎儿缺氧性酸血症对胎儿动脉收缩/舒张期血流速度比值无明显影响。

We operated on the pregnant sheep from 110 to 130 days of pregnancy. After performing cannulation of the carotic vessels, applying cardioelectrodes, and attaching an occluder of the umbilical cord, the fetuses were returned to the uterus to complete the gestational period. We monitored FHR pattern, fetal arterial blood pressure, umbilical arterial blood flow, intrauterine pressure, maternal arterial blood pressure continuously. After the fifth day of the operation, when blood gas value and FHR pattern pattern indicated the physiological state, at this point, we performed our experiments. The experiment was made of serial complete umbilical cord occlusion.We analyzed fetal and maternal blood gases, and measured plasma norepinephirine and epinephrine. The slope of the descending limb of the fetal heart rate deceleration curve decreased and correlated strongly with fetal arterial pH, bicarbonate, and logarithmic plasma norepinephrine and epinephrine concentration. During repeated umbilical cord compresion, the fetal acid-base and hormonal state was predicted by the fetal heart rate deceleration slope. When fetal acidemia progressed to an arterial pH of around 7.15, a characteristic overshoot acceleration was observed immediately after the release of cord compression. Fetal hypoxic acidemia induced by cord compression caused no change in the ratio of systolic/diastolic blood velocity when fetal arterial pH was as low as 7.15.