Discussion
renal impairment, seizures, seizure, hypertension, eclampsia, cerebral complications, cerebral artery blood flow, cerebral autoregulation impairment, hypertensive encephalopathy, abnormal cerebral autoregulation, cerebral injuries, preeclampsia
PREGNANCY-INDUCED HYPERTENSION, NEUROLOGICAL COMPLICATION, RENAL IMPAIRMENT, SEVERE PREECLAMPSIA, ECLAMPSIA, PRESSURE AREA, ADVERSE EFFECTS, HYPERTENSIVE ENCEPHALOPATHY, HYPERTENSION, PREECLAMPSIA AND ECLAMPSIA, PREECLAMPSIA
The most common cause of maternal mortality in preeclampsia is neurological complications. Hence, it is essential to understand the underlying pathophysiological mechanisms of these cerebral complications. Alteration of cerebral autoregulation and CPP in preeclampsia is a leading theory [Our study evaluated magnesium sulfate and labetalol medications, which are commonly used in our preeclampsia patients, with the CPP and CBFV endpoints by using the TCD.In the current study, both MgSO4 and labetalol were found to decrease CPP significantly at 1 and 6h after administration, with no significant change in the middle cerebral artery blood flow indices (MV, DIAS, and MCA velocity) indicating that the CPP reduction is due to the decrease in the blood pressure and not due to change in CBFV. Additionally, PI was found to be significantly decreased at 1 and 6h after administration of either MgSO4 or labetalol. However, the extent of CPP reduction and the blood flow indices did not differ significantly when labetalol was compared to MgSO4.Currently, severe preeclampsia and eclampsia are treated with magnesium sulfate [However, our findings of no significant change in MCA blood flow indices after magnesium sulfate administration question its role as a cerebral vasodilator. In accordance with our findings, Hatab et al. used a velocity-encoded phase-contrast magnetic resonance imaging technique and found no change in cerebral blood flow or the diameters of the middle and posterior cerebral arteries after 6-gram magnesium sulfate loading dose infusion in preeclampsia patients [The pulsatility index has been recognized to have a linear relationship with the intracranial pressure (ICP) and it is considered as an indirect estimate of ICP. Also, PI was reported to represent intracranial compliance and distal cerebral vascular resistance [Believing that CPP reduction might have a key role in the management of preeclampsia patients, our study findings could support this theory. Since MgSO4 administration decreased CPP while maintaining CBF in preeclampsia patients with severe features and elevated baseline CPP in our study,This discovery may also be a proposed mechanism of action for MgSO4 in seizure prevention.MgSO4 is well-known to obviously prevent eclamptic seizures and has been used for decades; it is currently recommended as the drug of choice for eclampsia prophylaxis [The same decrease in CPP with no effect on CBF in severe preeclampsia patients was also found after labetalol administration in the current study. The previous studies evaluating the effects of antihypertensive drugs on maternal cerebral hemodynamics of preeclampsia patients are scarce [The findings of our study showed that the mean values of SBP, DBP, and HR were significantly lower in the labetalol group after 1 hour of drug administration compared to the MgSO4 group and that parturients in the MgSO4 group were more likely to require an additional antihypertensive drug to achieve blood pressure target. Regarding the occurrence of seizures, there were no statistical difference between the two groups, seizures in the labetalol group was reported in 7 cases (23.3%) versus 4 cases (13.3%) in the magnesium group. 2 patients in the labetalol group was found to have renal impairment and they were adequately managed with no seizures occurred and no need to add MgSO4 which is known to require frequent monitoring of its serum levels in renal impairment patients. Rates of other adverse effects did not differ significantly between labetalol and MgSO4 groups.MgSO4 has been shown in previous studies to have an antihypertensive effect in patients with severe pregnancy-induced hypertension [Given the recognized role of cerebral autoregulation impairment and the hypertensive encephalopathy pathophysiological mechanism, and the fact that the challenge in severe preeclampsia patients is to reduce blood pressure and CPP without jeopardising CBF, our findings support the evidence of MgSO4’s ability to reduce CPP while maintaining CBF as a potential mechanism of action in severe preeclampsia patients with elevated baseline CPP.This CPP normalizing effect of MgSO4 was comparable with that of labetalol, which was found to reduce CPP with no effect on CBF in our enrolled patients. Therefore, labetalol, which has been used for many years in preeclampsia patients, is both effective and safe for controlling blood pressure and reducing CPP with no effect on CBF in these patients.Using labetalol with no magnesium sulfate was supported by several previous studies. Walker in his experience report demonstrated that labetalol was the only antihypertensive drug used in over 500 preeclampsia patients with no MgSO4 administration and only one of these patients had a seizure that may be due to inadequate blood pressure control [One of the main strengths of our study is that its prospective randomized comparative design comparing the cerebral hemodynamic effects of the two most commonly used drugs in preeclampsia patients. We suppose that the presented cerebral hemodynamic data add to the increasing evidence supporting the cerebral over perfusion pathophysiologic mechanism of cerebral injuries in preeclampsia with severe features.It is interesting to note that our study has several limitations including the small sample size that clearly is insufficient to address the safety issues. However, we believe that labetalol which has been used for many years is both effective and safe for controlling hypertension in preeclampsia. Secondly, the difficulty of accurately predicting preeclampsia patients with elevated CPP based on blood pressure alone. Although the CPP and blood pressure are obviously linked, they are not directly correlated in preeclampsia as abnormal cerebral autoregulation plays a vital role [