Transcranial Doppler measurement of cerebral velocity indices as a predictor of preeclampsia

OBJECTIVE: We have previously shown that women with preeclampsia demonstrate cerebral hyperperfusion and abnormal cerebrovascular autoregulation. In the current study, we tested the hypothesis that abnormal cerebrovascular function can be detected before the clinical onset of preeclampsia. STUDY DESIGN: Transcranial Doppler ultrasonography was performed for 166 women in the second trimester of pregnancy to measure peak, end-diastolic, and mean velocities in the middle cerebral arteries. Preeclampsia developed in 10 patients who were initially normotensive. In a nested case-controlled design, each patient with preeclampsia who was initially normotensive was matched for gestational age at the time of initial examination, maternal age, and parity with two pregnant women who remained normotensive and who were delivered at term. All measurements were performed with the subject in the left lateral position at baseline, during 5% carbon dioxide inhalation, and during a 2-minute isometric handgrip test. Blood pressure, heart rate, oxygen saturation, and end-tidal Pco₂ were recorded with each Doppler measurement. The mean pulsatility index, resistance index, and cerebral perfusion pressure at each time were calculated and compared. Statistical significance was set at a probability value of <.05. RESULTS: The studies were performed at 19 to 28 weeks of gestation. Preeclampsia developed an average of 13.6 ± 1.0 weeks after the study. Baseline mean blood pressure and heart rate were similar, but middle cerebral arteries pulsatility and resistance indices were lower in the women with preeclampsia who were initially normotensive compared with the pregnant women who were normotensive (0.83 and 0.54 vs 0.73 and 0.50, respectively; P < .05). Both maneuvers caused a significant reduction in the pulsatility and resistance indices. With the use of baseline values as covariates, no significant differences were noted in the response to either carbon dioxide inhalation or handgrip between the group of women who remained normotensive and the group of women with preeclampsia who were initially normotensive. CONCLUSION: Normotensive pregnant women who later have preeclampsia demonstrate lower baseline pulsatility and resistance indices but normal vasodilatory responses to challenge tests. These findings suggest that women who are destined to have preeclampsia experience cerebral hemodynamic changes that predate the development of overt preeclampsia symptoms.