EFFECT OF MAGNESIUM-SULFATE ON MATERNAL BRAIN BLOOD-FLOW IN PREECLAMPSIA - A RANDOMIZED, PLACEBO-CONTROLLED STUDY

OBJECTIVES: 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. STUDY DESIGN: 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. RESULTS: 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. CONCLUSIONS: 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.