Change in estimated cerebral perfusion pressure after treatment with nimodipine or magnesium sulfate in patients with preeclampsia

OBJECTIVE: Data are accumulating to suggest that cerebral perfusion pressur e may be either abnormally high or law in preeclampsia and eclampsia. Littl e is known of the cerebral perfusion pressure effects of magnesium sulfate or nimodipine. Our objective in this study was to compare the change in cer ebral perfusion pressure in patients with severe preeclampsia randomly sele cted to receive nimodipine or magnesium sulfate. STUDY DESIGN: Patients with severe preeclampsia were randomly selected to r eceive magnesium sulfate (6 g bolus and 2 g/hr intravenous infusion) or nim odipine (60 mg taken orally every 4 hours). Transcranial Doppler ultrasonog raphy was used to measure flow velocities in the right and left middle cere bral arteries, and the results were averaged. Measurements were obtained be fore treatment (baseline) and 30 minutes after the magnesium sulfate bolus was completely infused or 30 minutes after the nimodipine was ingested. Stu dies were performed before any other intervention. The person performing th e ultrasonography was unaware of the patient's group assignment. Estimated cerebral perfusion pressure was calculated with the following formula: Esti mated cerebral perfusion pressure = Velocity(mean) x [(Blood pressure(mean) - Blood pressure(diastolic))/(Velocity(mean) - Velocity(diastolic))]. The difference between estimated cerebral perfusion pressure at baseline and af ter treatment was compared between the 2 groups by means of the Mann-Whitne y rank sum test. RESULTS: Nine patients were randomly selected to receive nimodipine and 12 to receive magnesium sulfate. Patient demographics and severity of conditio n were not significantly different between the 2 groups. The change in esti mated cerebral perfusion pressure was significantly different between the g roups. Estimated cerebral pefusion pressure increased after nimodipine use and decreased after magnesium sulfate use. CONCLUSION: Shortly after administration to patients with severe preeclamps ia, nimodipine resulted in increased cerebral perfusion pressure in compari son with magnesium sulfate.