Persistence of cerebral hemodynamic changes in patients with eclampsia: A report of three cases

OBJECTIVE: This study was undertaken to compare the persistence of changes in estimated cerebral perfusion pressure and the resistance area product, a n index of cerebrovascular resistance, in women with preeclampsia and women with eclampsia. STUDY DESIGN: The maternal middle cerebral artery was evaluated by transcra nial Doppler ultrasonography in 6 patients with severe preeclampsia and 3 w omen with eclampsia, and cerebral blood flow velocities were determined. Es timated cerebral perfusion pressure was calculated according to the followi ng equation: Estimated cerebral perfusion pressure = Mean cerebral blood fl ow velocity/(Mean cerebral blood flow velocity - Diastolic cerebral blood f low velocity) x (Mean blood pressure - Diastolic blood pressure). Because t he diameters of the vessels could not be measured directly, an index of res istance was calculated according to the following equation: Resistance area product = Mean blood pressure/Mean cerebral blood flow velocity We calcula ted an index of cerebral blood flow according to the following equation: In dex = Estimated cerebral perfusion pressure/Resistance area product. Patien ts were reassessed at 24 and 48 hours after delivery. RESULTS: At the initial assessment the estimated cerebral perfusion pressur e was higher in women with eclampsia than in those with severe preeclampsia . In addition, cerebrovascular resistance was significantly decreased in th e eclampsia group, and it remained decreased as long as 4 days in 1 patient with eclampsia. CONCLUSIONS: Preeclampsia is associated with increases in cerebral perfusio n pressure counterbalanced by increases in cerebrovascular resistance, with no change in cerebral blood flow. In eclampsia a significant increase in c erebral perfusion pressure occurs, but a significant fall in cerebrovascula r resistance also occurs and a loss of autoregulation results in cerebral o verperfusion similar to that of hypertensive encephalopathy. This may persi st for as long as 4 days.