S. Gudmundsson, G. Ö. Gunnarsson, K.-H. Hökegård, J. Ingemarsson, I. Kjellmer
Venous Doppler velocimetry in relationship to central venous pressure and heart rate during hypoxia in the ovine fetus
Objective: Characteristic changes in ductus venosus
(DV) blood velocity and pulsations in the umbilical
vein (UV) have been described during imminent fetal
asphyxia. The aim of this study was to examine fetal
venous blood velocity in relationship to pressure gradient
across the DV during hypoxia in a fetal lamb preparation.
Methods: In general anesthesia, a cesarean section was
performed on seven pregnant ewes, the fetus was exteriorized
and put into a heated waterbath with uninterrupted
umbilical circulation. Pressure measurements
in the UV and inferior vena cava (IVC) were performed
with the catheter tips on both sides of the DV. Fetal
hypoxemia was induced by giving the ewe 12 % oxygen
in inhaling air. Pressure across the DV and Doppler velocimetry
were repeatedly measured during hypoxemia.
Blood velocity was recorded in the DV and UV by
Doppler ultrasound.
Results: Before hypoxia the median pressure gradient
across the DV was in systole 1 mmHg and 0.31 mmHg
in end-diastole and during hypoxemia 1.5 mmHg and
zero, respectively. The pressure difference across the
DV was constant during hypoxemia irrespective of the
presence of umbilical venous pulsations or heart rate.
IVC-pressure was greatly influenced by fetal heart rate
(FHR). A small but linear fall in systolic IVC pressure
was seen with increasing FHR. In end-diastole the IVC
pressure changed in a parabolic fashion, with increasing
pressure during brady- and tachycardia. Pulsations in
the UV also showed a parabolic relationship to FHR
and central venous pressure. DV end-systolic and end-diastolic
blood velocity changed during hypoxemia in
direct relationship to FHR and central venous pressure,
but without direct relationship to fetal blood gases.
Conclusion: The pressure gradient across the DV is
constant during hypoxemia.
Changes in central and umbilical venous pressure are
directly related to FHR. Umbilical venous and DV
blood velocity changed in direct relationship to FHR
and central venous pressure.
Journal of Perinatal Medicine, Walter de Gruyter
Print ISSN: 1619-3997
Volume: 27, 04/1999
Pages: 81 - 90
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