DDAVP-induced maternal hyposmolality increases ovine fetal urine flow

Efficacy of inhaled Desmopressin in pregnant women with idiopathic oligohydramnios - a randomized controlled trial

The aim of this study was to investigate the therapeutic effect of inhaled Desmopressin (DDAVP) in pregnant women with idiopathic oligohydramnios. This randomized, double-blind clinical trial involved 44 pregnant women at 28-37 weeks of gestation with idiopathic oligohydramnios admitted in 2 academic hospitals in Mashhad, Iran, from 2018 to 2019. In the intervention group, 10µg DDAVP was nasally sprayed. The control group received intravenous maintenance fluid. The hematocrit, electrolytes, blood pressure and urine-specific gravity were evaluated at baseline and 3, 8, and 24 hours later. Amniotic fluid index (AFI) was measured using ultrasound at baseline, 24 and 48 hours later. There was no significant difference in the basic characteristics (age, body mass index, and gestational age) between the two groups. The pattern of changes of AFI (baseline, 24 and 48 hours later) increased in the intervention (4.16±0.86, 7.08±1.453 and 7.76±1.62, p<0.001) and control groups (4.23±0.70, 5.39±1.079 and 5.68±1.10, p<0.001). Serum sodium levels significantly declined in the intervention group (p<0.001) but not in the control group (p=0.07). There were no significant differences in potassium (p=0.89), hematocrit (p=0.23), systolic blood pressure (p=0.21) and diastolic blood pressure (p=0.97). However, urine-specific gravity had an increasing pattern in the intervention group (p<0.001) and a decreasing pattern in the control group (p<0.001). This study showed that Desmopressin inhalation could increase the AFI and urine specific gravity, enhancing oligohydramnios treatment in pregnant women, compared to serum administration.

Central cholinergic mechanisms mediate swallowing, renal excretion, and c-fos expression in the ovine fetus near term

Fetal swallowing and renal metabolism contribute importantly to amniotic and body fluid homeostasis. To determine central cholinergic modulation of swallowing activity and renal excretion associated with neural activity, we examined the effects of intracerebroventricular injection of carbachol, a cholinergic agonist, in ovine fetuses at 0.9 gestation. Fetuses were chronically prepared with thyrohyoid, nuchal and thoracic esophagus, and diaphragm electromyogram electrodes, as well as lateral ventricle and vascular catheters. Electrodes were also implanted on the parietal dura for determination of fetal electrocorticogram (ECoG). After 5 days of recovery, fetal swallowing, ECoG, and urine output were monitored during basal period and the experimental period following intracerebroventricular injection of 0.9% NaCl as the control (n = 5) or carbachol (3 microg/kg, n = 5). Central carbachol did not significantly change fetal low voltage (LV) and high voltage (HV) ECoG temporal distributions. However, swallowing activity during LV ECoG was elevated significantly after intracerebroventricular carbachol. Associated with the swallowing activation, c-fos immunoreactivity in the putative dipsogenic center, subfornical organ, was enhanced significantly. The fetal urine flow rate and renal Na+, K+, and Cl(-) excretion were markedly increased following intracerebroventricular carbachol and sustained at the high level for at least 2 h. The results indicate that the central cholinergic mechanism is established and functional in regulation of fetal behavior and renal excretion at least at 0.9 gestation, which plays an important role in maintenance of fetal body fluid homeostasis.

Maternal DDAVP-induced hyponatremia preserves fetal urine flow during acute fetal hemorrhage

Maternal administration of DDAVP induces maternal and fetal plasma hyponatremia, accentuates fetal urine flow, and increases amniotic fluid volume. Fetal hemorrhage represents an acute stress that results in fetal AVP secretion and reduced urine flow rate. In view of the potential therapeutic use of DDAVP for pregnancies with reduced amniotic fluid volume, we sought to examine the impact of maternal hypotonicity during acute fetal hemorrhage. Chronically catheterized pregnant ewes (130 +/- 2 days) were allocated to control or to DDAVP-induced hyponatremia groups. In the latter group, tap water (2,000 ml) was administered intragastrically to the ewe followed by DDAVP (20 microg bolus, 4 microg/h) and a maintenance intravenous infusion of 5% dextrose water for 4 h to achieve maternal hyponatremia of 10-12 meq/l. Thereafter, ovine fetuses from both groups were continuously hemorrhaged to 30% of estimated blood volume over a 60-min period. DDAVP caused similar degree of reductions in plasma sodium and osmolality in pregnant ewes and their fetuses. In response to hemorrhage, DDAVP fetuses showed greater reduction in hematocrit than control fetuses (14 vs. 10%). Both groups of fetuses demonstrated similar increases in plasma AVP concentration. However, the AVP-hemorrhage threshold was greater in DDAVP fetuses (22.5%) than in control (17.5%). Hemorrhage had no significant impact on plasma osmolality, electrolyte levels, or cardiovascular responses in either group of fetuses. Despite similar increases in plasma AVP, DDAVP fetuses preserved fetal urine flow rates, with values threefold those of control fetuses. These results suggest that under conditions of acute fetal stress of hemorrhage, maternal DDAVP may preserve fetal urine flow and amniotic fluid volume.