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Changes in cerebral perfusion pressure in puerperal women with preeclampsia
K P Williams1, F Galerneau, S Wilson
1Department of Obstetrics and Gynaecology, Vancouver General Hospital, University of British Columbia, Canada. kwilliam@w.womenhosp.bc.ca
Objective:
To determine the variation in the estimated maternal cerebral perfusion and cerebrovascular resistance (the resistance area product) in the puerperium.
Methods:
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.
Results:
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).
Conclusion:
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.