Hypertension in Pregnancy

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Block C2 - Safe Motherhood & Neonates


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Chronic hypertension[edit]

Diagnosis[edit]

  • Precedes pregnancy.
  • High BP before 20th week.
  • 90% is essential. 10% is secondary.
  • To find underlying cause:
    • Urine analysis: to check for blood, protein, glucose, urea, and electrolytes.
    • Renal tract ultrasound.

Treatment[edit]

Anti-hypertensive drugs[edit]

  • Prevent:
    • Sudden increases in BP.
    • Cerebral hemorrhage.
    • Hypertensive encephalopathy.
  • Do not prevent:
    • Placental abruption.
    • Super-imposed preeclampsia.
    • Adverse perinatal outcome.
  • Start treatment when:
    • Sustained diastolic BP > 105-110 mmHg.
    • Systolic BP >= 160 mmHg.

Drugs used during pregnancy[edit]

  • Labetolol: Beta-adrenoceptor blocker that also blocks alpha-adrenoceptors.
  • A-Methyldopa: centrally acting alpha-adrenergic agonist that inhibits vasoconstricting impulses from medulla oblongata.
  • Nifedipine: calcium channel blocker.
    • Hampers thrombocyte aggregation.
    • Improves urine output within 24 hours of postpartum.
    • Has the equivalent effect of hydralazine and labetolol.
    • Lowers BP and gives a good perinatal outcome.
    • Does not increase the side effects when used together with MgSO4.
Class Drug Onset (minutes) Peak (minutes) Dosage
Arterial dilator Hydralazine 10-20 60 5-10 mg IV every 15-30 min
Calcium channel blocker Nifedipine 10 60 10-20 mg PO every 30 min
Alpha & beta blocker Labetolol 5 60 20-40-80 mg IV every 10-20 min (300 mg max)
Vein & arterial dilator Sodium nitroprusside 0.5-5 5 0.2-5.0 µg/kgBW/min

Drugs that should not be used during pregnancy[edit]

  • Angiotensin-converting-enzyme (ACE) inhibitors.
  • Angiotensin receptor blockers.
  • Diuretics.

Preeclampsia[edit]

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Gestational hypertension (hypertension during pregnancy) of:

  • BP >= 140/90 mmHg on two separate occasions measured at least 4 hours apart.
  • Proteinuria > 300 mg in 24 hours of urine collection.
  • Arising after the 20th week of gestation in a previously normotensive woman.
  • Resolving completely by the 6th postpartum week.

Pathophysiology[edit]

  • Failure of the second wave of trophoblast invasion during 16-20 weeks gestation and failure to destroy the muscularis layer of spiral arterioles.
  • The continuum theory: exaggerated form of the inflammatory response, occurring in response to relative increase of trophoblastic debris released from a poorly perfused placenta.
  • Endothelial dysfunction.
  • Multisystem affected.
  • Progressive.
  • Unpredictable course of disease.
  • The only treatment is delivery.

Prevention[edit]

  • Calcium supplements.
  • Low dose aspirin.

Management[edit]

  • Stress reduction.
  • Assessment of fetal and maternal state.
  • Fluid balance.
  • Management of complications.
  • Eclampsia prophylaxis.
  • Consider time and mode of delivery.
  • Magnesium sulfate (MgSO4):
    • Normally only used in obstetric cases.
    • Superior to phenytoin for prophylaxis.
    • Superior to phenytoin or diazepam in preventing recurrences.
    • 2-4 g IV dose followed by 1-2 g/hour IV or 4 g IM/6 hours.
    • Side effects: weakness, paralysis, cardiac toxicity.
    • Monitor: reflex, respiration, and level of consciousness.

When to induce baby delivery[edit]

  • If patient has gestational hypertension only, deliver only if >= 37 weeks.
  • If patient has severe preeclampsia, deliver only if >= 34 weeks.
  • Deliver in < 34 weeks, in case of:
    • Uncontrollable BP.
    • Lab evidence showing involvement of multiple organs.
    • Suspected fetal distress.
    • Uncontrolled seizures.
    • Symptoms not responsive to therapy.

Referral[edit]

Consider referral if the resources are limited and conditions of mother / fetus allows

  • BP and maternal symptoms are stable.
  • Fetal status good.
  • Appropriate anti-hypertensive drugs are started.
  • MgSO4 given if eligible.
  • Discussion with the patient and family.
  • MgSO4 and anti-hypertensives can be potentially fatal if overdosed.

Postpartum management of hypertension[edit]

  • BP usually rises progressively over the first five days after after delivery.
  • BP peaks at 3-6 days after delivery.
  • 10% of maternal deaths are attributed to postpartum hypertensive disorders.
  • Rapid and complete resolution within six weeks of delivery.
  • There is risk of cardiovascular disease and renal disease for several years after delivery.