The effect of acute or short term hypoxia on fetal and maternal cardiovascular hemodynamics has been well known, however, little is known about the effect of long term hypoxemia. To determine the animals hemodynamic responses to this stress we studied 3 groups of animals 1) pregnant ewes (n=20) 110 to 115 days of gestation, subjected to hypoxia for up to 28 days, 2) pregnant ewes (n=4) which served as normoxic controls, and 3) non pregnant ewes (n=6) subjected to hypoxemia for up to 28 days. We measured maternal and fetal mean arterial pressure (Bp), heart rate (HR), arterial PO2, O2 saturation (HbO2), hemoglobin (Hb), Hematocrit (Hct), blood volume (BV), and erythropoeitin (Ep) for at least 17 days. In addition we also measured maternal arteriovenous O2 difference (ΔA-V), uterine blood flow (Qut) uterine vascular resistance (VRut) and uterine O2 uptake (VO2ut). Fetal cortisol, epinephrine (Epi) and norepinephrine levels were also measured. In the pregnant hypoxic group arterial PO2 decreased from a control value of 101.5 ± 5.1 Torr to 59.2 ± 5.1 Torr within a few minutes, where it remained throughout the study. The concentration of hemoglobin increased from 8.9 ± 0.5 g/dl to 10.0 ± 0.5 g/dl within 24 h where it remained, while erythropoietin concentration increased from 16.6 ± 2.1 mU/ml to 39.1 ± 7.8 mU/ml at 24 h, but then returned to control levels. Arterial O2 content, glucose concentration, mean arterial pressure, and cardiac output decreased slightly. m contrast, body weight, heart rate, blood volume, uterine blood flow, uterine O2 flow, uteroplaoental O2 uptake and the concentrations of catecholamines and cortisol remained relatively constant. For the fetuses, within a few minutes of hypoxia, arterial Po2, decreased from control value of 29.7 ± 2.1 Torr to 19.1 + 2.1 Torr, where it remained. Hemoglobin increased from 10.0 ± 1.0 g/dl to 12.9 ± 1.0 g/dl by day 7 where it remained. This was associated with an increase of [Ep] from 22.8+2.2 mn/ml to 144 ± 37 mu/ml within 24 h, but by day 7 it had returned to levels slightly above normal. Epinephrine also increased moderately and remained elevated throughout the study. However, value of mean arterial pressure and heart rate did not differ from controls. Thus in response to long term hypoxemia of moderate severity both pregnant and nonpregnant sheep experience relatively minor cardiovascular and hematologic responses. Perhaps surprisingly, these fetuses were able to compensate, so that at term their body weights were normal, 3.77 ± 0.2 kg.
Lawrence D. Longo
Charles A. Ducsay
Raymond D. Gilbert
Master of Science (MS)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Anoxia; Pregnancy Complications; Pregnancy, Animal; Placenta
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This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.
Siu, Benjamin L., "Maternal and Fetal Responses to Long-Term Hypoxemia in Sheep" (1989). Loma Linda University Electronic Theses, Dissertations & Projects. 1627.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives