Noninvasive assessment of the maternal cerebral circulation by transcranial Doppler ultrasound during angiotensin II infusion.

Objective: To examine the relationship between experimentally induced increments in blood pressure and maternal middle cerebral artery flow velocity patterns measured by transcranial Doppler ultrasound (TCD).
Design: Prospective experimental study.
Setting: John Radcliffe Maternity Hospital, Oxford.
Intervention: Middle cerebral artery flow velocity waveforms were measured using 2 MHz pulsed Doppler ultrasound via the temporal cranial approach at 28 weeks gestation before, during and 10 min following an angiotensin II infusion.
Subjects: 101 normotensive primiparous women at 28 weeks gestation.
Results: A significant rise in blood pressure and fall in heart rate were demonstrated between pre-infusion and maximum angiotensin II infusion (maximum blood pressure) recordings. Simultaneous changes were observed in all flow velocity indices, shown as a decrease in systolic velocity and pulsatility index, and an increase in diastolic and mean velocity (P < 0.0001). These values all returned to baseline levels 10 min post infusion (P < 0.0001). Statistical analysis suggested that the change in flow velocity is related to the rise in blood pressure rather than the direct effect of angiotensin II on the cerebral circulation.
Conclusion: Transcranial Doppler can detect changes in the cerebral circulation associated with alterations in blood pressure during pregnancy. The technique needs to be evaluated further in hypertensive disease.