Effect of the Loading Dose of Magnesium Sulfate (MgSO4) on the Parameters of Doppler Flow Velocity in the Uterine, Umbilical and Middle Cerebral Arteries in Severe Preeclampsia

Abstract

Objective. To evaluate Doppler velocimetry parameters (resistance index [RI], pulsatility index [PI] and systolic/diastolic [S/D] ratio) of maternal-fetal circulation before and after magnesium sulfate administration in pregnant women with severe preeclampsia. Methods. A prospective observational cohort analysis of 40 women with severe preeclampsia was performed. Doppler ultrasonography scans were performed before and 20 minutes after intravenous administration of magnesium sulfate. Maternal parameters such as heart rate, and systolic, diastolic and mean arterial pressure were recorded. Doppler flow velocity parameters (RI, PI and S/D ratio) were evaluated in the uterine, umbilical and middle cerebral arteries. The different mean values obtained before and after magnesium sulphate were analyzed using the paired t-test. Results. There was a statistically significant increase in mean maternal heart rate and a statistically significant decrease in systolic, diastolic and mean maternal blood pressure before and after administration of magnesium sulphate (p < 0.001). Resistance index decreased in the umbilical (p = 0.003; 95% CI: 0.008 - 0.03) and middle cerebral artery (p = 0.001; 95% CI: 0.01 - 0.05) and in both uterine arteries. Likewise, there was a significant reduction in the PI and S/D ratio in all the arteries assessed. Conclusions. Maternal administration of intravenous magnesium sulfate in preeclampsia leads to an increase in maternal heart rate and a decrease in systolic, diastolic and mean arterial blood pressure. A reduction in the resistance index, pulsatility index and S/D ratio was recorded in the uterine, umbilical and cerebral arteries.