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.