Itskovitz J, Goetzman B W, Roman C, Rudolph A M
Am J Physiol. 1984 Oct;247(4 Pt 2):H655-60. doi: 10.1152/ajpheart.1984.247.4.H655.
The effect of reducing hemoglobin affinity for O2 on fetal oxygenation was assessed in seven fetal lambs in which fetal blood was almost completely replaced by maternal blood 2-3 days postoperatively. Measurements of fetal blood gases and organ blood flow (radionuclide-labeled microsphere technique) were obtained before and 1 h after the exchange transfusion. Umbilical venous blood PO2 increased from 29 +/- 5 to 35 +/- 6 (SD) Torr (P less than 0.001) but hemoglobin O2 saturation decreased from 78.2 +/- 10.3 to 39.8 +/- 8.8% (P less than 0.001), resulting in a 46% decrease in umbilical venous blood O2 content. Since umbilical-placental blood flow also decreased (P less than 0.002), O2 delivery to the fetus decreased by 64% (P less than 0.002). Although O2 extraction increased from 32.5 +/- 6.8 to 50.9 +/- 9.0% (P less than 0.002), fetal O2 consumption fell from 7.28 +/- 1.97 to 4.10 +/- 1.20 ml X min-1 X kg-1 (P less than 0.02), and metabolic acidemia developed. No significant change in fetal cardiac output was observed. Blood flow increased significantly to the myocardium and adrenals but fell in the placenta, carcass, and lungs and was maintained in other organs. This resulted in a significant decrease in the amount of O2 delivered to all fetal organs except to the myocardium in which it was maintained. In the sheep the higher affinity of fetal blood hemoglobin for O2 helps maintain normal oxygenation during fetal life by facilitating O2 uptake at the placenta and unloading O2 in the tissues.
在七只胎羊中评估了降低血红蛋白对氧气的亲和力对胎儿氧合的影响，这些胎羊在术后2 - 3天胎儿血液几乎完全被母体血液替代。在换血输血前和输血后1小时进行胎儿血气和器官血流（放射性核素标记微球技术）测量。脐静脉血PO₂从29±5升至35±6（标准差）托（P＜0.001），但血红蛋白氧饱和度从78.2±10.3降至39.8±8.8%（P＜0.001），导致脐静脉血氧含量下降46%。由于脐 - 胎盘血流量也减少（P＜0.002），输送到胎儿的氧气减少了64%（P＜0.002）。尽管氧摄取率从32.5±6.8升至50.9±9.0%（P＜0.002），胎儿氧消耗量从7.28±1.97降至4.10±1.20毫升·分钟⁻¹·千克⁻¹（P＜0.02），并出现代谢性酸血症。未观察到胎儿心输出量有显著变化。心肌和肾上腺的血流量显著增加，但胎盘、躯体和肺的血流量减少，其他器官的血流量保持不变。这导致输送到除心肌外所有胎儿器官的氧量显著减少，而心肌的氧量保持不变。在绵羊中，胎儿血液血红蛋白对氧气的较高亲和力通过促进在胎盘摄取氧气并在组织中释放氧气，有助于在胎儿期维持正常的氧合。
