Objective: To research the cerebral hemodynamic effects of labetalol in pregnant women with hypertension.
Design: Prospective observational study.
Setting: Tertiary Care Medical Center.
Population: Pregnant patients with hypertension.
Methods: Transcranial Doppler (TCD) ultrasound was used to measure the blood velocity in the middle cerebral arteries (MCA) of eight pregnant patients with hypertension, before and after the administration of a 200 mg oral dose of labetalol. Five patients had severe preeclampsia, and three had chronic hypertension with superimposed preeclampsia. MCA blood velocity and systemic blood pressure were measured simultaneously at the baseline, and at 60 and 180 min after labetalol. Selected cerebral hemodynamic parameters were compared with normative curves. Values outside of the 5th and 95th percentiles were regarded as abnormal.
Main outcome measures: Cerebral perfusion pressure (CPP), resistance area product (RAP), and cerebral flow index (CFI).
Results: Patient age, gestational age, and parity were similar to those of the normal women from whom the normative data were obtained. Women with hypertension had higher baseline CPP, MAP, and RAP than normal pregnant women, but their CFI was within the normal range. Labetalol reduced the CPP, as well as the systolic, diastolic, and mean BP significantly at 60 and 180 min without significantly affecting the heart rate, MCA velocities, RAP, or CFI.
Conclusions: Labetalol effectively reduces CPP, without affecting cerebral perfusion, primarily by a decrease in systemic blood pressure. This makes it an ideal agent for blood pressure control in severely hypertensive pregnant women.