Fetal placental embolization in the late-gestation ovine fetus: Alterations in umbilical blood flow and fetal heart rate patterns - 12/09/11
Abstract |
OBJECTIVE: Our goal was to determine the effect of chronic and acute umbilical-placental embolization on placental hemodynamic and fetal heart rate patterns in relation to fetal oxygenation in the near-term ovine fetus. STUDY DESIGN: Daily fetal placental embolization was performed during 10 days in 9 sheep fetuses until fetal arterial oxygen content decreased by ~30%. Nine control fetuses received saline solution. Mean and pulsatile umbilical blood flow, perfusion pressure, placental vascular resistance, fundamental impedance, pressure pulsatility index, and umbilical artery resistance index corrected to a fetal heart rate of 160 beats/min were measured. On day 10 both groups were acutely embolized until fetal arterial pH decreased to ~7.00. Fetal heart rate was measured with the Sonicaid System 8000 (Oxford Sonicaid, Oxford, United Kingdom). RESULTS: Chronic fetal placental embolization was associated with a progressive reduction in umbilical blood flow (p < 0.00001) and fetal arterial oxygen content (p < 0.001) whereas fetal heart rate patterns remained unaltered. A chronic increase in umbilical artery resistance index corrected to a fetal heart rate of 160 beats/min could be entirely explained only if the changes in umbilical artery pressure pulsatility index and the fundamental impedance were taken into account, in addition to the changes observed in placental vascular resistance. During acute embolization leading to a 50% reduction in umbilical blood flow (p < 0.0002) and a three times increase in placental vascular resistance (p < 0.0001), the most consistent change in fetal heart rate patterns related to progressive metabolic acidosis was an 84% decrease in absolute acceleration frequency (p < 0.0001) whereas short-term fetal heart rate variability remained unaltered. CONCLUSION: Changes in umbilical artery resistance index induced by chronic umbilical-placental embolization resulting in fetal hypoxemia occurred before any changes in fetal heart rate patterns were detectable. A decrease in the absolute acceleration frequency was the only component of fetal heart rate patterns related to progressive metabolic acidosis in the near-term ovine fetus. (AM J OBSTET GYNECOL 1996;175:63-72.)
Le texte complet de cet article est disponible en PDF.Keywords : Fetal heart rate, umbilical blood flow, fetal oxygenation
Plan
From the Departments of Obstetrics and Gynaecology and Physiology, St. Joseph's Health Centre, Lawson Research Institute, Medical Research Council Group in Fetal and Neonatal Health and Development, University of Western Ontario. |
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Supported by the Medical Research Council of Canada. |
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Reprint requests: Robert Gagnon, MD, Department of Obstetrics and Gynecology, St. Joseph's Health Centre, 268 Grosvenor St., London, Ontario, Canada N6A 4V2. |
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0002-9378/96 $5.00 + 0 6/1/70678 |
Vol 175 - N° 1
P. 63-72 - juillet 1996 Retour au numéroBienvenue sur EM-consulte, la référence des professionnels de santé.
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