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This Article Full Text Full Text (PDF) All Versions of this Article: 286/4/H1266    most recent 00523.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Acharya, G. Articles by Rasanen, J. Search for Related Content PubMed PubMed Citation Articles by Acharya, G. Articles by Rasanen, J.

Relationships among Doppler-derived umbilical artery absolute velocities, cardiac function, and placental volume blood flow and resistance in fetal sheep

¹Department of Obstetrics and Gynecology, University Hospital of Northern Norway, N-9038 Tromsø, Norway; and Departments of ²Anesthesiology and ³Obstetrics and Gynecology, University of Oulu, 90220 Oulu, Finland

Submitted 6 June 2003 ; accepted in final form 17 November 2003

We hypothesized that umbilical artery (UA) absolute blood flow velocities measured by Doppler ultrasonography reflect placental volume blood flow (Q_UA) and placental vascular resistance (R_UA) in a late gestation fetal sheep model. In addition, we examined the relationships between umbilical artery absolute blood flow velocities and parameters of fetal cardiac function. Twenty-six sheep fetuses were instrumented at 112–132 days of gestation. After a 5-day recovery period, experiments were performed under general anesthesia in 16 normal fetuses, in 5 fetuses after maternal administration of phenylephrine, and in 5 fetuses after placental embolization. The Q_UA and arterial blood pressures were measured using a transit-time ultrasonic flow probe and a catheter placed into the descending aorta, respectively. UA peak systolic velocity (PSV), end-diastolic velocity (EDV), time-averaged maximum velocity (TAMXV), pulsatility index (PI), mean velocity (V_mean), fetal cardiac output, ventricular ejection forces, and the proportion of isovolumetric relaxation time (IRT%) in the cardiac cycle were measured with the use of Doppler ultrasonography. Significant positive linear correlations were found between UA EDV, TAMXV, and V_mean versus Q_UA, whereas UA PI had a significant negative correlation with Q_UA. Significant negative correlations were shown between UA EDV, TAMXV, and V_mean versus R_UA. A significant positive correlation was present between UA PI and R_UA. Doppler-derived UA parameters did not correlate with fetal arterial blood pressures, cardiac output, ventricular ejection forces or IRT%. In fetal sheep, Doppler-derived UA PI and absolute velocities, except PSV, are closely related to directly measured Q_UA and R_UA, validating the use of noninvasive Doppler velocimetry in the assessment of placental circulation.

fetal hemodynamics; placental circulation