title: Fetal oxygenation and Doppler ultrasonography of cardiovascular hemodynamics in a chronic near-term sheep model.
abstract: OBJECTIVE
  We hypothesized that a decrease in fetal oxygenation without acidemia in a near-term fetal sheep leads to cardiovascular hemodynamic changes that are detectable by Doppler ultrasonography.
  
  
  METHODS
  Twelve ewes and fetuses were instrumented at 112 to 127 days of gestation. After a 5-day recovery period, experiments were performed with general anesthesia. Uterine and placental volume blood flows and fetal arterial and venous blood pressures were measured. Fetal cardiovascular hemodynamics was assessed by Doppler ultrasonography. All the measurements were performed at baseline, during fetal hypo-oxygenation, and at recovery phase.
  
  
  RESULTS
  A drop in fetal Po2 was related to increased (P < .05) weight-indexed right ventricular and combined cardiac outputs and proximal branch pulmonary artery pulsatility index values. The increase in proximal branch pulmonary artery pulsatility index values correlated (R = .59; P < .05) with the decrease in fetal oxygen saturation. In the aortic isthmus, the time-velocity integral ratio between antegrade and retrograde blood flow components decreased (P < .05) when fetal Po2 dropped.
  
  
  CONCLUSIONS
  During decreased fetal oxygenation Doppler ultrasonography demonstrated increased fetal cardiac output and pulmonary arterial vascular impedance and a relative increase in the retrograde blood flow component in the aortic isthmus.
authors.affiliation: Department of Obstetrics and Gynecology, University of Oulu, Oulu, Finland. kaarin.makikallio@oulu.fi
authors.forename: Kaarin
authors.initials: K
authors.lastname: Mäkikallio
authors.forename: Tiina
authors.initials: T
authors.lastname: Erkinaro
authors.forename: Niina
authors.initials: N
authors.lastname: Niemi
authors.forename: Tomi
authors.initials: T
authors.lastname: Kavasmaa
authors.forename: Ganesh
authors.initials: G
authors.lastname: Acharya
authors.forename: Mervi
authors.initials: M
authors.lastname: Päkkilä
authors.forename: Juha
authors.initials: J
authors.lastname: Räsänen
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis; D002302:Cardiac Output / Q000502:physiology; D002319:Cardiovascular System / Q000196:embryology*; D005260:Female; D005333:Fetus / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D011247:Pregnancy; D011651:Pulmonary Artery / Q000502:physiology; D011673:Pulsatile Flow / Q000502:physiology; D012756:Sheep; D013318:Stroke Volume / Q000502:physiology; D018608:Ultrasonography, Doppler; D016216:Ultrasonography, Prenatal; D014655:Vascular Resistance / Q000502:physiology