SIGNIFICANCE OF A DIASTOLIC NOTCH IN THE UTERINE ARTERY FLOW VELOCITYWAVE-FORM INDUCED BY UTERINE EMBOLIZATION IN THE PREGNANT EWE

Objective To investigate the relation between placental embolisation a nd the diastolic notch in the uterine artery flow velocity waveform of pregnant ewes under general anaesthesia. Methods Seven pregnant ewes at a gestation 16 to 17 weeks were anaesthesized and microbeads of gel foam were injected into the uterine artery; changes in the uterine cir culation were assessed by Doppler velocimetry. Results Gelfoam embolis ation reduced uterine blood flow in a dose-dependent manner, from a me an (95% CI) of 568 mL/min (495-641) to 159 mL/min (131-187) after the injection of 30 mg of gelfoam, and increased the uterine vascular resi stance from 135 mmHg.min.L-1 (103-167) to 498 mmHg.min.L-1 (422-574). A diastolic notch in uterine artery flow velocity waveform was observe d after 20 mg to 25 mg of gelfoam in two ewes and after injection of 3 0 mg of gelfoam in all seven animals. Injection of 30 mg of gelfoam in creased the pulsatility index to 2.4 (1.9-2.9) from 0.6 (0.5-0.7). The mean uterine vascular resistance at the time of the appearance of a d iastolic notch was 414 mmHg.min.L-1 (377-451). Conclusion These findin gs suggest that an elevated pulsatility index and the presence of a di astolic notch in the uterine artery flow velocity waveform are indicat ors of increased uterine vascular resistance and impaired uterine circ ulation.