Transcranial assessment of maternal cerebral blood flow velocity in normal vs. hypertensive states. Variations with maternal posture.

This study compared the effect of a change in maternal posture on maternal cerebral blood flow velocity assessed transcranially in normal vs. various hypertensive groups. Ten normotensive, 10 preeclamptic and 10 chronically hypertensive patients had maternal middle cerebral artery (MCA) blood flow velocity assessed in three positions--left lateral decubitus, supine and sitting upright--using 2-mHz transcranial Doppler ultrasound. Comparison was then made of the effect of a change in posture on cerebral blood flow velocity in each group using analysis of variance with Student's t test for statistical significance. Normotensive and chronically hypertensive women showed minimal changes in MCA blood flow velocity, while preeclamptic women showed a 30% rise in all aspects of MCA blood flow velocity from the left lateral decubitus to sitting up. In preeclamptic women, MCA blood flow velocity, which showed a significant rise with changes in posture, was not accompanied by significant changes in blood pressure and so is not a secondary response to a change in cardiac output but may be a primary effect of local circulatory changes.