Changes in cerebral perfusion pressure in puerperal women with preeclampsia.

Abstract

To determine the variation in the estimated maternal cerebral perfusion and cerebrovascular resistance (the resistance area product) in the puerperium. The maternal middle cerebral artery was evaluated by transcranial Doppler ultrasound in ten women 2 days before labor, in 21 women in early labor and at 24 and 48 hours postpartum, and in 6 women at 1 week postpartum. Cerebral blood flow velocities were determined. Women were diagnosed initially with mild preeclampsia. Estimated cerebral perfusion pressure was Vmean/[Vmean - Vdiastolic] [BPmean - BPdiastolic]. Because the diameter of the vessels could not be measured directly, an index of resistance was calculated: the resistance area product = BPmean/velocitymean. We calculated an index of cerebral blood flow to be estimated cerebral perfusion pressure divided by resistance area product. Our study had a power of 80% to detect a 16-cm/second increase in middle cerebral blood flow velocity. Estimated maternal cerebral perfusion was maintained for up to 1 week postpartum. Cerebrovascular resistance did not change in the puerperium. Cerebral blood flow index (+/-standard deviation) was significantly increased at 1 week postpartum compared with early labor levels (28.3 +/-6.9 versus 46.7+/-15.6, respectively) (P < .05). Cerebral blood flow 1 week postpartum increased significantly over early labor values. These persistent changes in the cerebral vasculature might put patients at risk for seizures up to 1 week postpartum.