Effect of magnesium sulfate on maternal brain blood flow in preeclampsia: a randomized, placebo-controlled study.

Abstract

The purpose of this study was to determine the effect of a 6 gm intravenous bolus of magnesium sulfate on maternal brain blood flow velocity waveforms in patients with preeclampsia. Twelve patients with preeclampsia were randomized to two groups and studied with Doppler ultrasonography before and immediately after infusion of either a 6 gm intravenous loading dose of magnesium sulfate or a placebo. The middle cerebral, common carotid, and internal carotid arteries were studied. Magnesium sulfate significantly reduced the pulsatility index in the middle cerebral artery (change in pulsatility index = -0.16 + 0.09) when compared with the placebo (change in pulsatility index = -0.02 + 0.06), p = 0.01. There were no significant changes in the Doppler indexes of the carotid vessels. These data suggest that magnesium sulfate vasodilates the smaller-diameter intracranial vessels distal to the middle cerebral artery and may exert its main effect in the prophylaxis and treatment of eclampsia by relieving cerebral ischemia.