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

METHODS:

• 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

RESULTS:

• 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

CONCLUSION:

• 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”

Learn more – Primary Sources:

Intravenous labetalol versus oral nifedipine for acute hypertension in pregnancy: effects on cerebral perfusion pressure

Related ObG Topics:

ACOG Guidance: Emergency Treatment for Severe Hypertension in Pregnancy

Labetalol or Nifedipine for Acute Elevated BP in Pregnancy?

Severe Hypertension in Pregnancy: Which Oral Medication is Optimal When IV Access is Limited?