Gilson G J, Mosher M D, Conrad K P
Department of Physiology, University of New Mexico School of Medicine, Albuquerque 87131.
Am J Physiol. 1992 Dec;263(6 Pt 2):H1911-8. doi: 10.1152/ajpheart.1992.263.6.H1911.
Knowledge about possible alterations in cardiac output (CO), total peripheral vascular resistance (TPVR), and their time course and magnitude of change is conspicuously lacking for the conscious gravid rat. Therefore, we assessed CO using Fick methodology in unrestrained, chronically instrumented, conscious rats. The rats were studied during early (day 7), mid (day 13), or late gestation (day 18) along with nonpregnant control rats matched with respect to age and days postsurgery. Significant differences between pregnant and nonpregnant rats were observed during midgestation, when CO was increased by 26 +/- 12% and TPVR was decreased by 23 +/- 9% in the pregnant animals. These changes were accompanied by a narrowed arterial-mixed venous oxygen content difference (AVD; P < 0.05 vs. nonpregnant). In late gravid rats, CO was higher than nonpregnant values by 49 +/- 8%, and TPVR was lower by 34 +/- 7% (both P < 0.05). Oxygen consumption and carbon dioxide production were significantly increased, and AVD further narrowed when compared with the nonpregnant control group. With the exception of absent chronic respiratory alkalosis in pregnant rats, we conclude that cardiovascular and respiratory changes in conscious, gravid rats and in pregnant women are comparable. We speculate that the ultimate purpose of many of these adaptations is to increase CO so that oxygen delivery and the supply of nutrients to the uteroplacental units are sufficient or more than sufficient to meet oxygen and nutrient demands. At midgestation, the rise in CO seems to anticipate the oxygen needs of the nascent uteroplacental units.
对于清醒的妊娠大鼠，目前明显缺乏关于心输出量（CO）、总外周血管阻力（TPVR）可能发生的变化及其时间进程和变化幅度的相关知识。因此，我们采用菲克法在未受束缚、长期植入仪器的清醒大鼠中评估心输出量。在妊娠早期（第7天）、中期（第13天）或晚期（第18天）对大鼠进行研究，并与年龄和术后天数匹配的未孕对照大鼠进行比较。在妊娠中期观察到妊娠大鼠和未孕大鼠之间存在显著差异，此时妊娠动物的心输出量增加了26±12%，总外周血管阻力降低了23±9%。这些变化伴随着动脉-混合静脉血氧含量差（AVD）缩小（与未孕大鼠相比，P<0.05）。在妊娠晚期大鼠中，心输出量比未孕时的值高49±8%，总外周血管阻力低34±7%（均P<0.05）。与未孕对照组相比，耗氧量和二氧化碳产生量显著增加，AVD进一步缩小。除妊娠大鼠不存在慢性呼吸性碱中毒外，我们得出结论，清醒妊娠大鼠和孕妇的心血管和呼吸变化具有可比性。我们推测，许多这些适应性变化的最终目的是增加心输出量，以便向子宫胎盘单位输送足够或超过足够的氧气和营养物质，以满足氧气和营养需求。在妊娠中期，心输出量的增加似乎预示着新生子宫胎盘单位的氧气需求。
