绵羊胎儿在长期缺氧时，尿流量增加但未出现羊水过多。

Matsumoto L C, Cheung C Y, Brace R A

Division of Perinatal Medicine, Department of Reproductive Medicine, University of California at San Diego. La Jolla 92093-0802, USA.

Am J Obstet Gynecol. 2001 Apr;184(5):1008-14. doi: 10.1067/mob.2001.112971.

OBJECTIVE

In the ovine fetus subjected to 24 hours of hypoxia, urinary flow is normal within a few hours from the onset of hypoxia and there is a maintained inhibition of swallowing. We hypothesized that 4 days of fetal hypoxia would lead to polyhydramnios.

STUDY DESIGN

Five late-gestation fetal sheep were subjected to hypoxia for 4 days and 7 other late-gestation fetal sheep served as time control animals. Fetal hypoxia was produced on postsurgical days 5 through 9 by continuous intratracheal nitrogen insufflation to the ewe. On days 3, 5, 7, and 9 after surgery, amniotic fluid volume, fetal urinary flow rate, and the compositions of maternal and fetal blood, amniotic fluid, and fetal urine were measured. A 3-factor analysis of variance was used for statistical analysis.

RESULTS

During the period of experimental hypoxia the mean (+/-SE) fetal PaO(2) was 16.0 +/- 0.6 mm Hg, versus 21.2 +/- 0.7 mm Hg in control sheep (P <.001). Fetal hypoxia was associated with increased urinary flow on days 7 and 9, averaging 1410 +/- 310 and 2101 +/- 345 mL/d, respectively, versus 585 +/- 92 and 699 +/- 78 mL/d, respectively, in control animals (P <.001). Amniotic fluid volume was unchanged with time and averaged 960 +/- 159 mL in hypoxic fetuses on postsurgical days 7 through 9 and 851 +/- 130 mL in control animals (P =.60). Fetal blood lactate increased in the hypoxic animals, averaging 3.4 +/- 2.1 mmol/L versus 1.6 +/- 0.3 mmol/L in control animals (P =.02). Fetal urinary excretions of sodium, potassium, chloride, and lactate increased significantly during hypoxia, by 170% to 400%.

CONCLUSION

Four days of nitrogen-induced hypoxia in the ovine fetus resulted in excess fetal urinary flow approximating 1000 mL/d greater than normal without the development of polyhydramnios. Because amniotic fluid volume did not change and hypoxia is a known inhibitor of fetal swallowing, we speculate that intramembranous absorption of amniotic water, electrolytes, and lactate increased.

目的

在经历24小时缺氧的绵羊胎儿中，缺氧开始后数小时内尿流正常，但吞咽持续受到抑制。我们假设胎儿缺氧4天会导致羊水过多。

研究设计

5只妊娠晚期的胎儿绵羊接受4天的缺氧处理，另外7只妊娠晚期的胎儿绵羊作为时间对照动物。在手术后第5至9天，通过向母羊持续气管内注入氮气来制造胎儿缺氧。在手术后第3、5、7和9天，测量羊水量、胎儿尿流率以及母血、胎儿血、羊水和胎儿尿液的成分。采用三因素方差分析进行统计分析。

结果

在实验性缺氧期间，胎儿平均（±标准误）动脉血氧分压（PaO₂）为16.0±0.6 mmHg，而对照绵羊为21.2±0.7 mmHg（P<.001）。胎儿缺氧与第7天和第9天尿流增加有关，平均分别为1410±310和2101±345 mL/天，而对照动物分别为585±92和699±78 mL/天（P<.001）。羊水量随时间未发生变化，缺氧胎儿在手术后第7至9天平均为960±159 mL，对照动物为851±130 mL（P = 0.60）。缺氧动物胎儿血乳酸增加，平均为3.4±2.1 mmol/L，对照动物为1.6±0.3 mmol/L（P = 0.02）。缺氧期间胎儿尿中钠、钾、氯和乳酸的排泄显著增加，增加了170%至400%。