Vasopressin Effects on Lung Liquid Volume in Fetal Sheep

Abstract

The normal switch from placental to pulmonary gas exchange at birth requires rapid removal of liquid from the lungs. Previous reports contend that vasopressin may be important in regulating this process, but this notion derives from studies in which fetal sheep received very large doses of vasopressin that yielded plasma concentrations at least 10 times greater than those that have been measured during normal labor. To study the physiologic effects of vasopressin on lung liquid volume in fetal sheep, we made three sets of experiments. First, we measured plasma vasopressin concentrations [VP] in 15 late-gestation fetal sheep, five of which were at various stages of spontaneous labor. [VP] in these fetuses ranged from <1 (prelabor) to 31 (during labor) pU/mL; postmortem extravascular lung water (EVLW) ranged from 4.5 to 14.5 gig dry lung tissue. In a second series of studies, we measured EVLW in five sets of near-term (138 + 1 d, term = 147 d) twin fetal sheep that received an 8-h i.v. infusion of either isotonic saline (control twin) or AVP (AVP-treated twin) at a rate of -1 (mU/kg)/min. This dose was chosen to mimic [VP] measured in fetuses that had been studied during labor.[VP] did not change in the control twins, whereas [VP] increased from 1.8 + 1.0 to 27.7 + 3.5 pU/mL in treated twins. There was a small, statistically significant difference in EVLW between twins that received AVP and untreated twins (11.9 + 1.8 versus 14.6 + 2.8 gig dry lung). In a third series of studies, we measured net production of lung liquid (Jv) by an indicator dilution technique in 16 fetal sheep that received an i.v. infusion of isotonic saline for 2 h followed by AVP for up to 8 h.[VP] averaged 23.4 t 6.5 pU/mL during AVP infusion. For six fetuses that were studied at <I32 d (128 + 4 d) gestation, Jv did not change during AVP infusion (11.1 t 6.7 mL/h versus control, 10.2 + 4.7 mL/h); for 10 fetuses >I32 d (135 + 2 d) gestation, Jv decreased from 11.3 + 4.7 mL/h during the control period to 8.6 During fetal life, the lungs are filled with liquid that forms as a result of epithelial C1-secretion into the lumen of the developing respiratory tract (1). Rapid removal of this liquid from potential airspaces is an essential step in establishing an effective switch from placental to pulmonary gas exchange at

Arginine Vasopressin and Copeptin in Perinatology

“…Compared to vaginal delivery, infants delivered by cesarean section have a significantly increased risk of neonatal admission because of respiratory complications mainly due to delayed lung fluid reabsorption after birth, namely wet lung ( 121 ). AVP has been shown to decrease the production of fetal lung liquid in ovine fetuses ( 122 ), and it has been shown that AVP is involved in liquid removal from the lungs at birth ( 123 – 125 ). Thus, it might be speculated that, in the absence of preconditioning, when primary cesarean section was performed, AVP administration shortly after birth to the baby, e.g., via nasal spray, might represent a novel strategy to support postnatal adaptation.…”

Cardiovascular Biomarkers in Amniotic Fluid, Umbilical Arterial Blood, Umbilical Venous Blood, and Maternal Blood at Delivery, and Their Reference Values for Full-Term, Singleton, Cesarean Deliveries

“…After birth, clearing fluid from the lungs to establish sufficient respiration is important. Vasopressin helps to clear pulmonary fluid (8). This indicates that biomarkers representing different physiological actions, such as natriuretic peptides and vasopressin/copeptin, are relevant for sufficient pulmonary function of newborns.…”

Fetal Release of Copeptin in Response to Maternal Oxytocin Administration

“…More particularly, there is evidence that AVP itself, which we measured using its surrogate marker copeptin, specifically supports adaptation of the lung, including alveolar fluid reabsorption and surfactant secretion. 21,35,36 In conclusion, oxytocin challenge test-induced contractions suffice to elevate fetal levels of copeptin and inferentially those of AVP. This result is an argument in favor of a trial designed to lower neonatal respiratory morbidity after elective cesarean delivery by a preemptive intervention that increases fetal copeptin levels.…”