656 Fetal hypoxia induced by partial maternal aortic occlusion is tolerated in a lamb model

Abstract

Hemorrhage is a leading cause of maternal mortality. Resuscitative endovascular balloon occlusion of the aorta (REBOA) has been used for hemorrhage control in obstetrical patients, however the fetal effects are unknown. Preliminary data from a pregnant ewe model showed that fetal physiologic changes from partial aortic occlusion (pREBOA) first occur at mean placental arterial pressure (pMAP) 40mmHg, however data are lacking on fetal neurological outcomes. We aimed to further evaluate the effects of decreased pMAP on the fetus in a sheep model. A REBOA catheter was placed in the infrarenal aorta of four gravid term ewes. pMAP was approximated by maternal femoral MAP. The REBOA balloon was inflated to decrease pMAP to 40mmHg, then decreased in 5mmHg increments to a fetal SaO2 of 15%. Fetal hemodynamics, SaO2, pH, and lactate were monitored via right fetal carotid arterial lines. At fetal SaO2 15%, the REBOA was deflated followed by a recovery period. pREBOA was then repeated twice as part of a separate study. Data from the first round are presented here. Post-mortem fetal brain magnetic resonance imaging (MRI) was performed to evaluate for ischemia. Mean baseline pMAP was 57.5±6.2mmHg and it was decreased to 40mmHg (n=1), 30mmHg (n=2), and 25mmHg (n=1) prior to recovery. Fetal SaO2 was significantly lower than baseline (58.5±7.4%) at each decreased pMAP (p<0.0001, Fig 1A). Fetal heart rate did not significantly increase until pMAP 25mmHg (baseline 133.5±8.8 vs. 156±14.1, p=0.001, Fig 1B). Fetal pH and lactate did not significantly change until pMAP 30mmHg (pH 7.22±0.02 vs. 7.14±0.1, p=0.01; lactate 1.9±0.4 vs. 3.5±2.8, p=0.004). After 3 rounds of hypoxia, there was no evidence of ischemia on fetal brain MRIs (Fig 2). Fetal SaO2, heart rate, pH, and lactate did not change significantly until a relatively low pMAP. After three rounds of progressive hypoxia from pREBOA, there was no evidence of fetal brain ischemia on MRI. Future studies in a survival model are needed to evaluate neurologic function after maternal pREBOA.View Large Image Figure ViewerDownload Hi-res image Download (PPT)