Fetal oxygenation and Doppler ultrasonography of cardiovascular hemodynamics in a chronic near-term sheep model

• Published in: American journal of obstetrics and gynecology 2006-02, Vol.194 (2), p.542-550
• Main Authors: Mäkikallio, Kaarin, Erkinaro, Tiina, Niemi, Niina, Kavasmaa, Tomi, Acharya, Ganesh, Päkkilä, Mervi, Räsänen, Juha
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Blood Gas Analysis; Cardiac Output - physiology; Cardiovascular System - embryology; Doppler ultrasonography; Female; Fetal sheep; Fetus - physiology; Gynecology. Andrology. Obstetrics; Heart Rate - physiology; Hemodynamics - physiology; Medical sciences; Oxygen; Physiology; Pregnancy; Pulmonary Artery - physiology; Pulsatile Flow - physiology; Sheep; Stroke Volume - physiology; Ultrasonography, Doppler; Ultrasonography, Prenatal; Vascular Resistance - physiology
• ISSN: 0002-9378; 1097-6868
• DOI: 10.1016/j.ajog.2005.08.028

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. 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. A drop in fetal P o 2 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 P o 2 dropped. 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.