Bernstein D, Teitel D F, Rudolph A M
Cardiovascular Research Institute, University of California, San Francisco 94143.
Pediatr Res. 1988 Jun;23(6):621-7. doi: 10.1203/00006450-198806000-00019.
The cardiovascular adaptations to chronic anemia were studied in the newborn lamb and then compared with the adaptations to chronic hypoxemia. Eight chronically instrumented newborn lambs underwent repeat isovolemic exchange transfusions to maintain their Hb concentrations at 60% of normal for age. Hemodynamic studies were performed twice weekly for 2 wk after which time regional blood flows were measured using radionuclide-labeled microspheres. The major compensatory responses after 2 wk of anemia were moderate increases in heart rate (229 +/- 20 versus 187 +/- 15 beats/min) and cardiac output (226 +/- 36 versus 165 +/- 38 ml/kg/min), an increase in fractional extraction of oxygen (65 versus 40%), and a redistribution of regional blood flow. Blood flows to the heart and brain increased whereas blood flows to the viscera and carcass did not change. These compensatory responses were different from those that occur during chronic hypoxemia: specifically, cardiac output did increase, growth was not suppressed, and the pattern of redistribution of regional blood flows was different. The dissimilar effects of anemia (decreasing systemic oxygen content) versus hypoxemia (decreasing systemic oxygen tension) on local tissue receptors and peripheral chemoreceptors may account for these differences.
在新生羔羊中研究了心血管系统对慢性贫血的适应性，然后将其与对慢性低氧血症的适应性进行比较。八只长期植入仪器的新生羔羊接受反复等容交换输血，以将其血红蛋白浓度维持在同龄正常水平的60%。在2周内每周进行两次血流动力学研究，之后使用放射性核素标记的微球测量局部血流量。贫血2周后的主要代偿反应是心率适度增加（229±20次/分钟对187±15次/分钟）和心输出量增加（226±36毫升/千克/分钟对165±38毫升/千克/分钟），氧分数提取增加（65%对40%），以及局部血流重新分布。流向心脏和大脑的血流量增加，而流向内脏和躯体的血流量没有变化。这些代偿反应与慢性低氧血症期间发生的反应不同：具体而言，心输出量确实增加，生长未受抑制，局部血流重新分布的模式也不同。贫血（降低全身氧含量）与低氧血症（降低全身氧张力）对局部组织受体和外周化学感受器的不同影响可能解释了这些差异。
