وازوموتور راکتیویتی مغز(Cerebrovascular Reactivity) در حاملگی نرمال و پره‌اکلامپسی

    Background & Aim: Preeclampsia is the major cause of maternal and perinatal morbidity and mortality. Transcranial Doppler(TCD) as a noninvasive procedure is used to assess hemodynamic changes in middle cerebral artery(MCA). Knowing the influence of normal pregnancy and preeclampsia on brain hemodynamics is essential for proper management of anesthesia, labor and vasoactive drug usage in these patients. The aim of the present study is to evaluate and compare vasomotor reactivity in normal pregnancy and preeclampsia. Patients and Method: In this case-control study, transcranial Doppler ultrasound was used to measure peak systolic velocity(PSV), end-diastolic velocity(EDV), mean flow velocity(MV), and pulsatility index(PI) in the middle cerebral artery(MCA) of 16 preeclamptic and 15 normotensive pregnant women in the third trimester. Cerebral vasomotor reactivity(VMR) was measured as percentage of changes in peak flow velocity after inhaling 5% co2 for 1-2 minutes. Statistical analysis was done using independent t-test and Fisher Exact test. Results: There was no significant difference in terms of maternal age, gestational age and gravidity between the two groups. Preeclamptic women had higher baseline peak(113.3 compared with 76.31 cm/s, P<0.001), end diastolic(59.1 compared with 38.4cm/s, P<0.001) and mean velocity(73.8 compared with 46.1 cm/s, P<0.001). In comparison to normotensive group, preeclamptic women showed a significant decrease in vasomotor reactivity(4.41% compared with 8.51%, P<0.001). Conclusion: Preeclamptic patients had elevated baseline peak, end-diastolic and mean velocity in the MCAs and decreased VMR in reaction to 5% co2 inhalation. These findings are consistent with a state of vasoconstriction in preeclamptic women which is unresponsive to stimuli that under normal circumstances result in vasodilation. Cerebral edema, hemorrhage, ischemia, and convulsion are all considered as complications developing in preeclampsia or eclampsia. The precise etiology of these complications is unknown but they might be seen due to vascular disturbance. Under normal circumstances, autoregulation maintains the blood flow of the brain subject to a wide range of changes in systemic blood pressure. It seems that autoregulation malfunctions in preeclampsia. Abnormal response given to cerebral perfusion pressure by cerebral vessels might have a role in pathophysiology of cerebral dysfunction which is seen in preeclampsia.