Avaliação do efeito do sulfato de magnésio sobre a hemodinâmica cerebral na pré-eclâmpsia grave através da dopplervelocimetria

Abstract

Introduction: Preeclampsia (PE) complicates 5% to 10% of all pregnancies. It is the main cause of maternal mortality worldwide. Brain complications, such as eclampsia, account for 75% of deaths. Magnesium sulfate (MgSO4) is recommended for prevention of eclampsia in severe PE; however, its mechanism of action is still unknown. Ophthalmic artery Doppler is a non-invasive exam that provides important data about the cerebral circulation. Due to this characteristic, the ocular Doppler may help in the study of the mechanism of prevention of eclampsia by MgSO4. Objective: To describe the Doppler velocimetric indices of the ophthalmic artery in women with severe PE and single gestation before and after the use of MgSO4. Correlate the results of ophthalmic artery Doppler findings to the recognized protective effect of MgSO4 on cerebral arterial blood flow in pregnancies affected by severe PE. Materials and methods: Patients with single pregnancy, absence of labor and criteria for initiation of MgSO4 for maternal neuroprotection, defined as the presence of severe hypertension and signs suggestive of eclampsia were included in the study. All patients received intravenous hydralazine until blood pressure reached levels lower than 160 mmHg and / or 110 mmHg. The flow of the right ophthalmic artery was evaluated before the onset of MgSO4, and at 10, 30 and 60 minutes after the drug was started. The pulsatility index (PI), the resistance index (IR) and the peak ratio (PR) in ocular Doppler were evaluated. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were assessed at all times of ocular Doppler. The data collected were submitted to statistical analysis. The significance level of 5% was adopted for all statistical tests. Results: Eighteen patients were evaluated. There was an increase in IR and PI values, with no statistical significance, and a statistically significant decrease in PR after administration of magnesium sulphate. There was a statistically significant reduction of SBP and DBP in the evaluations performed. No statistically significant change in HR was observed. Conclusion: The decrease in PR reflects an increase in the impedance to the flow in the ophthalmic artery and, consequently, the reduction of cerebral perfusion after the use of MgSO4. This reduction may explain the mechanism by which MgSO4 protects against brain injury in severe PE, preventing acute seizures in these patients, since the most accepted theory currently suggests that in severe PE there is impairment of self-regulation of cerebral blood flow, leading to hyperflow, responsible for brain damage