Siimes A S, Creasy R K, Heymann M A, Rudolph A M
Am J Obstet Gynecol. 1978 Sep 1;132(1):42-8. doi: 10.1016/0002-9378(78)90796-2.
The response of the fetal circulation to beta adrenergic stimulation with ritodrine hydrochloride has been investigated by long-term monitoring of the fetal lamb in utero. Ritodrine was infused intravenously either into the ewe or directly into the fetus, and cardiovascular and acid-base responses were measured. Fetal cardiac output and its distribution were measured with the use of radionuclide-labeled microspheres. The output of each ventricle also was measured by means of long-standing implanted electromagnetic flow transducers around the ascending aorta or pulmonary trunk during infusion of ritodrine at various rates into the fetus. Infusion of ritodrine (1.9 mcg. per kilogram per minute) into the ewe caused no change in fetal heart rate, blood pressure, cardiac output, or umbilical blood flow, but did cause an increase in fetal adrenal and myocardial blood flow. Ritodrine infused directly into the fetus produced a marked increase in fetal heart rate and a minimal change in cardiac output. There were no significant changes in fetal or maternal acid-base balance during the ritodrine infusions.
通过对子宫内胎羊进行长期监测，研究了胎儿循环对盐酸利托君β肾上腺素能刺激的反应。将利托君静脉注射到母羊体内或直接注射到胎儿体内，并测量心血管和酸碱反应。使用放射性核素标记的微球测量胎儿心输出量及其分布。在以不同速率向胎儿输注利托君期间，还通过长期植入在升主动脉或肺动脉干周围的电磁流量传感器测量每个心室的输出量。向母羊输注利托君（每分钟每千克1.9微克）不会导致胎儿心率、血压、心输出量或脐血流量发生变化，但会导致胎儿肾上腺和心肌血流量增加。直接向胎儿输注利托君会使胎儿心率显著增加，而心输出量变化极小。在输注利托君期间，胎儿或母体的酸碱平衡没有显著变化。
