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Keywords:

  • Doppler;
  • uterine artery;
  • uteroplacental circulation;
  • volume blood flow

Abstract

Objective

To test the hypothesis that Doppler-derived (calculated) uterine artery volume blood flow (cQUtA) reflects accurately volume blood flow measured directly (mQUtA) in an experimental setting.

Methods

Five pregnant sheep were instrumented at 122–130 days of gestation under general anesthesia. After a 4-day recovery period, maternal hemodynamics were varied by administering to the sheep under general anesthesia noradrenaline, beta-blocker, low oxygen gas mixture, epidural bupivacaine and ephedrine, consecutively. The central venous pressure was obtained with the help of a thermodilution catheter. The mean arterial pressure and acid–base status were monitored using a 16-gauge polyurethane catheter inserted into the descending aorta via a femoral artery. A 6-mm transit-time ultrasonic perivascular flow probe was used to measure the mQUtA. Doppler ultrasonography of the uterine artery was performed and volume blood flow was obtained simultaneously by the transit-time ultrasonic perivascular flow probe during each phase of the experiment.

Results

A total of 31 observations were made. The mQUtA varied between 90 and 800 (mean ± SD, 419 ± 206) mL/min during the experiments. The corresponding values for the cQUtA were 110 and 900 (mean ± SD, 459 ± 211) mL/min. There was a significant correlation (R = 0.76; P < 0.0001) between mQUtA and cQUtA. The mQUtA correlated positively with Doppler-derived uterine artery absolute velocities, i.e. peak systolic (R = 0.50; P = 0.004), end-diastolic (R = 0.53; P = 0.002) and time-averaged maximum (R = 0.69; P < 0.0001) and time-averaged intensity weighted mean (R = 0.75; P < 0.0001) velocities.

Conclusion

cQUtA correlates well with volume blood flow measured directly. Doppler-derived uterine artery absolute blood flow velocities reflect uteroplacental volume blood flow in pregnant sheep. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.