Barnard J M, Chaffin D, Droste S, Tierney A, Phernetton T
Department of Obstetrics and Gynecology, University of Wisconsin Medical School, Madison, USA.
Obstet Gynecol. 1995 May;85(5 Pt 1):669-74. doi: 10.1016/0029-7844(95)00023-k.
To determine the effects of maternal abdominal carbon dioxide (CO2) insufflation on placental blood flow and fetal blood gas measurements in the pregnant ewe.
Five time-bred ewes at 110 days' gestation were surgically prepared with maternal and fetal catheters placed for subsequent measurement of vascular pressures, blood gas tensions, and placental blood flows. On surgical recovery day 3, the ewe was anesthetized, placed on her right side, intubated, and manually ventilated to maintain a constant maternal carbon dioxide pressure (PCO2) range (37.1 +/- 3.3 mmHg) for the duration of the experiment. The maternal abdomen was inflated with CO2 to maintain an intraabdominal pressure of 20.7 +/- 0.6 mmHg. Maternal and fetal blood flows and blood gases were determined at 30 minutes of ventilation, 60 minutes of insufflation, and 40 minutes of desufflation. Simultaneous maternal and fetal organ blood flows were determined using the radioactive microsphere technique.
Maternal perfusion pressure fell 22% (P = .01) in response to insufflation, whereas pressure in the inferior vena cava rose 53% (P = .003). Maternal placental blood flow fell to 61% (P = .002) of control. Seventy-seven percent of this blood-flow change was in response to the decreased perfusion pressure, with 23% resulting from an increased placental vascular resistance of 32% (P = .02). Maternal blood gas values did not change with insufflation or desufflation. Despite the marked decrease in maternal placental blood flow, the fetal placental perfusion pressure and blood flow, pH, and blood gas tensions were unaffected by insufflation or desufflation.
The sheep fetus has sufficient placental flow reserves or compensatory responses to maintain adequate gas exchange during a 1-hour, 20 mmHg maternal pneumoperitoneum. Laparoscopic surgical procedures may prove to be a safe alternative to laparotomy during pregnancy.
确定母羊腹部二氧化碳（CO₂）注入对妊娠母羊胎盘血流及胎儿血气测量的影响。
选取5只妊娠110天的经产母羊，通过手术置入母羊和胎儿导管，用于后续血管压力、血气张力及胎盘血流的测量。在术后恢复第3天，将母羊麻醉，使其右侧卧位，进行气管插管并手动通气，在实验过程中维持母羊二氧化碳压力（PCO₂）在恒定范围（37.1±3.3 mmHg）。向母羊腹部注入CO₂以维持腹腔内压力在20.7±0.6 mmHg。在通气30分钟、注入CO₂ 60分钟及排出CO₂ 40分钟时测定母羊和胎儿的血流及血气。使用放射性微球技术同时测定母羊和胎儿的器官血流。
注入CO₂后母羊灌注压下降22%（P = 0.01），而下腔静脉压力升高53%（P = 0.003）。母羊胎盘血流降至对照值的61%（P = 0.002）。该血流变化的77%是由于灌注压降低所致，23%是由于胎盘血管阻力增加32%（P = 0.02）。母羊血气值在注入或排出CO₂时未发生变化。尽管母羊胎盘血流显著减少，但胎儿胎盘灌注压、血流、pH及血气张力不受注入或排出CO₂的影响。
在母羊气腹压力为20 mmHg、持续1小时的情况下，绵羊胎儿具有足够的胎盘血流储备或代偿反应以维持充分的气体交换。腹腔镜手术在孕期可能被证明是剖腹手术的安全替代方法。
