Preeclampsia may cause both overperfusion and underperfusion of the brain - A cerebral perfusion based model

Background. The hypothesis was that low cerebral perfusion pressure is more common in women with mild preeclampsia as compared to those with severe pr eeclampsia,, while high cerebral perfusion pressure is more common In women with severe preeclampsia than in women with mild preeclampsia. Design. Prospective, observational study. Setting. University teaching hospitals. Methods. Transcranial Doppler ultrasound was used to measure the blood velo city in the middle cerebral arteries of 54 patients with mild preeclampsia and 44 patients with severe preeclampsia. Blood pressure was measured simul taneously. Cerebral perfusion pressure was calculated and plotted on the sa me axes as data from 63 normal pregnant women. Data outside of the 95% pred iction limits were regarded as abnormal. All studies were, prior to labor, and before volume expansion or treatment. Analysis: Student's t-test, Mann Whitney U test, and Fisher's exact test as appropriate with two-tailed p<0. 05. Main outcome measure: The number of patients in each group with cerebra l perfusion pressure values outside the normal 95% prediction limits. Results. Almost the same number of women with mild (21/54=39%) and severe ( 15/44=34%) preeclampsia had measurements within the normal range (p=0.78). Mild preeclamptic women were more likely to have low (28/54=52%) rather tha n high cerebral perfusion pressure (p<0.001), while severe preeclamptics we re more likely to have high cerebral perfusion pressure (26/44=59%) than lo w (p<0.001). Conclusions. In preeclampsia the brain can be normally perfused, underperfu sed and overperfused. Although many women with mild preeclampsia will have underperfusion (52%), and a significant number of women with severe preecla mpsia will have overperfusion (59%), many preeclamptic women have. cerebral perfusion within the normal range.