van de Walle A F, Martin C B
Eur J Obstet Gynecol Reprod Biol. 1986 Apr;21(4):253-60. doi: 10.1016/0028-2243(86)90025-0.
The effects of ritodrine, 15 micrograms X min-1 X kg-1 administered intravenously, on the maternal circulation and uteroplacental blood flow were investigated in eight chronically catheterized pregnant guinea pigs near term. Cardiac output and its distribution were measured by means of the radionuclide-labelled microsphere technique before, and after 2 and 6 h of infusion of ritodrine. Ritodrine produced a sustained elevation of cardiac output to 135 and 137% of the control value after 2 and 6 h, respectively. The carcass and gastrointestinal tract together accounted for the greatest portion of the extra blood flow, 77 and 84% at the times of the two flow measurements during treatment. After 2 h of ritodrine, mean placental blood flow was reduced to 85% of the control level (n.s.), uteroplacental vascular resistance was 127% of its initial value (n.s.), and the placental fraction of cardiac output had decreased from 18 to 12% (P less than 0.02). Continuation of the infusion to 6 h resulted in an increase in mean placental blood flow to 107% of the control value and return of uteroplacental vascular resistance to its initial level. The placental fraction of cardiac output increased to 14%, significantly (P less than 0.05) different from both the initial and the 2-h values. Blood flow to the skin, lungs, spleen and mammary glands decreased between the 2- and 6-h flow measurements. These observations are compatible with the hypothesis that the changes in uteroplacental blood flow during administration of ritodrine are passive, resulting from the balance between the increase in cardiac output and vasodilatation in extrauterine vascular beds.
在8只临近足月、长期插管的妊娠豚鼠中，研究了静脉注射利托君（15微克·分钟⁻¹·千克⁻¹）对母体循环和子宫胎盘血流的影响。在输注利托君前、输注2小时和6小时后，采用放射性核素标记微球技术测量心输出量及其分布。利托君分别在输注2小时和6小时后使心输出量持续升高至对照值的135%和137%。躯体和胃肠道共占额外血流的最大部分，在治疗期间两次血流测量时分别为77%和84%。利托君输注2小时后，平均胎盘血流量降至对照水平的85%（无统计学意义），子宫胎盘血管阻力为初始值的127%（无统计学意义），心输出量的胎盘部分从18%降至12%（P<0.02）。持续输注至6小时导致平均胎盘血流量增加至对照值的107%，子宫胎盘血管阻力恢复至初始水平。心输出量的胎盘部分增加至14%，与初始值和2小时时的值均有显著差异（P<0.05）。在2小时和6小时的血流测量之间，皮肤、肺、脾和乳腺的血流量减少。这些观察结果与以下假设一致，即利托君给药期间子宫胎盘血流的变化是被动的，是由心输出量增加和宫外血管床血管舒张之间的平衡所致。
