Grand Rounds

Labetalol vs Nifedipine for Preeclampsia: How do they Affect Cerebral Perfusion Pressure?

BACKGROUND AND PURPOSE:

Women with preeclampsia have elevated cerebral perfusion pressure
Tolcher et al. (AJOG, 2020) compared cerebral perfusion pressure before and after IV labetalol vs oral nifedipine during severe hypertension in pregnancy

Prospective cohort study
Participants
- Between 24 and 42 weeks gestation | Severe hypertension
- Exclusion criteria: Active labor |Received other antihypertensive medication within 2 hours of initial cerebral perfusion pressure measurement
Exposures
- Labetalol group: 20 mg IV
- Nifedipine group: 10 mg oral
Study design
- Severe hypertension: SBP ≥160 and/or DBP ≥110
- Peripheral blood pressure and transcranial MCA Doppler studies obtained
  - Before medication administration
  - 30 minutes after medication administration
- Cerebral perfusion pressure can be measured with non-invasive transcranial Doppler
Multiple baseline data were obtained, including
- Maternal age | Parity | Race and ethnicity | BMI Gestational age | Pre-existing diabetes or hypertension | FGR | Magnesium sulfate
Primary outcome
- Change in cerebral perfusion pressure

16 women were enrolled | 8 women in each group
- No significant baseline characteristic differences between groups
There was a significantly greater decrease in the following 30 minutes after the administration of oral nifedipine vs IV labetalol for the following
- Systolic blood pressure (P = 0.003)
  - Intravenous labetalol: -9.8 mmHg
  - Oral nifedipine: -39 mmHg
- Mean arterial pressure (P = 0.02)
  - Intravenous labetalol: -7.1 mmHg
  - Oral nifedipine: -22.3 mmHg
- Cerebral perfusion pressure (P = 0.01)
  - Intravenous labetalol: -2.5 mmHg
  - Oral nifedipine: -27.7 mmHg
There was no statistically significant difference in
- Diastolic pressure (P = 0.15)
  - Intravenous labetalol: -12.9 mmHg
  - Oral nifedipine: -5.4 mmHg
- Change in middle cerebral artery velocity by transcranial Doppler (P = 0.64)
  - Intravenous labetalol: 0.07 cm/s
  - Oral nifedipine: 0.16 cm/s

Cerebral perfusion pressure was significantly decreased following a single dose of oral nifedipine vs IV labetalol in patients with severe hypertension in the setting of preeclampsia
The evidence suggests that this decrease is not due to a change in cerebral blood flow but rather a decrease in peripheral arterial blood pressure
The authors note that future research should include Doppler measurements of anterior and especially posterior cerebral arteries as “most neuropathology in the setting of preeclampsia occurs in the occipital region”

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