Skillman C A, Plessinger M A, Woods J R, Clark K E
Am J Physiol. 1985 Dec;249(6 Pt 2):H1098-105. doi: 10.1152/ajpheart.1985.249.6.H1098.
Graded reductions in uteroplacental blood flow (UBF), produced by an externally adjustable vascular occluder, were studied in unanesthetized pregnant sheep. This method was designed to simulate the physiological occurrence of reduced UBF to study its effects on fetal status. Sheep were divided into four groups in which average percent changes (+/- SE) in UBF, as measured by electromagnetic flow probes, were 7 +/- 2, -24 +/- 1, -49 +/- 1, and -63 +/- 2% for 1 h. Maternal and fetal cardiovascular (heart rate and blood pressure) and blood gas measurements of PO2 and PCO2, pH, and O2 content were determined before, during, and after recovery from UBF reduction. UBF reduction had no significant effect on maternal measurements. Changes in fetal PO2 and O2 content were directly related to the extent of vascular occlusion (P less than or equal to 0.05). Fetal pH markedly decreased after 1 h of 49% UBF reduction (P less than or equal to 0.05) and within 10 min after 63% UBF reduction (P less than or equal to 0.05). Fetal bradycardia (P less than or equal to 0.05) resulted from 63% reduction in UBF. Fetal heart rates at recovery were greater than base-line heart rate values (P less than or equal to 0.05) in the three groups whose UBF was restricted. The results of the present study suggest that the uterus of the pregnant ovine is perfused in sufficient excess to protect the fetus during short-term reductions of less than 50% UBF.
在未麻醉的妊娠绵羊中，研究了通过外部可调节血管闭塞器产生的子宫胎盘血流量（UBF）分级减少的情况。该方法旨在模拟UBF减少的生理现象，以研究其对胎儿状态的影响。绵羊被分为四组，通过电磁流量探头测量，每组UBF的平均变化百分比（±标准误）在1小时内分别为7±2%、-24±1%、-49±1%和-63±2%。在UBF减少前、减少期间及恢复后，测定母羊和胎儿的心血管指标（心率和血压）以及血气指标PO2、PCO2、pH和O2含量。UBF减少对母羊的测量指标无显著影响。胎儿PO2和O2含量的变化与血管闭塞程度直接相关（P≤0.05）。在UBF减少49% 1小时后（P≤0.05）以及UBF减少63% 10分钟内（P≤0.05），胎儿pH显著下降。UBF减少63%导致胎儿心动过缓（P≤0.05）。在UBF受限的三组中，恢复时胎儿心率高于基线心率值（P≤0.05）。本研究结果表明，在短期UBF减少小于50%的情况下，妊娠绵羊的子宫有足够的灌注量来保护胎儿。
