Hypertensive disorders in pregnancy

O10.0/O11/O14.0-2/O14.9

DESCRIPTION

Hypertensive disorders are one of the most common direct causes of maternal mortality and are responsible for significant perinatal and maternal morbidity. These disorders include chronic hypertension, pre-eclampsia, eclampsia and HELLP Syndrome. Early detection and timely intervention is essential to prevent maternal and perinatal complications.

Preeclampsia

Preeclampsia is hypertension with significant proteinuria developing for the first time after 20 weeks of gestation, and can also be superimposed on chronic hypertension - evidenced by the new onset (after 20 weeks’ gestation) of persistent proteinuria in a woman who had an initial diagnosis of chronic hypertension .

Pre-eclampsia without severe features:

A diastolic BP of 90-109 mmHg and/or systolic BP of 140-159 mmHg; but no symptoms or organ dysfunction.

Maternal features of severe disease:

  • Acute severe hypertension (diastolic BP of 110 mmHg and/or systolic >160 mmHg).
  • Thrombocytopenia (platelet <100 000/μL).
  • Impaired liver function (ALT or AST >40 IU/L).
  • Severe persistent right upper quadrant or epigastric pain.
  • HELLP syndrome (platelets <100 000 and AST >70 µl and LDH >600 µl).
  • Serum creatinine ≥120 micromol/L.
  • Pulmonary oedema.
  • New-onset severe headache unresponsive to medication.
  • Visual disturbances.

GENERAL MEASURES

Bed rest, preferably in hospital.
Lifestyle adjustment and diet.
Monitor BP, urine output, renal and liver function tests, platelet count, proteinuria and fetal condition.
Consider delivery when risks to mother outweigh risks of prematurity to baby.

MEDICINE TREATMENT

Treatment

Antihypertensives

Medicine treatment will be dictated by blood pressure response.
Monitor progress until a stable result is achieved.
In general, diuretics are contra-indicated for hypertension in pregnant women.
When needed, combine drugs using lower doses when BP >160/100 mmHg, before increasing single medication doses to a maximum.

LoEIII [11]

  • Methyldopa, oral, 250 mg 8 hourly as a starting dose.
    • Increase to a maximum of 750 mg 8 hourly, according to response .

LoEIII [12]

AND/OR

  • Amlodipine, oral, 5 mg daily.
    • Increase to 10 mg daily.

Hypertensive emergency

SBP ≥160 mmHg and/or DBP ≥110 mmHg. Admit to a high-care setting for close monitoring.

  • Nifedipine, oral, 10 mg.
    • Repeat after 30 minutes if needed, until systolic blood pressure <160 mmHg and diastolic blood pressure < 110 mmHg.
    • Swallow whole. Do not chew, bite or give sublingually.

LoEIII [13]

If unable to take oral or inadequate response:

  • Labetalol, IV infusion, 2 mg/minute to a total of 1–2 mg/kg.
    • Reconstitute solution as follows:
      • Discard 40mL of sodium chloride 0.9% from a 200 mL container.
      • Add 2 vials (2 x 100 mg) of labetalol (5 mg/mL) to the remaining 160 mL of sodium chloride 0.9% to create a solution of 1 mg/mL.
      • Start at 40mL/hour to a maximum of 160 mL/hour.
      • Titrate against BP – aim for BP of 140/100 mmHg.
    • Once hypertensive crisis has been resolved, switch to an oral preparation.

LoEI [14]

Delivery

  • Oxytocin, IM, 10 units as a single bolus after delivery of the baby.

LoEIII [15]

Ergot-containing medicines are contraindicated in hypertensive women, including pre-eclampsia, following delivery of the baby.

Pre-eclamptic and eclamptic women are often hypovolaemic, particularly when the haematocrit exceeds 40%, but are also susceptible to pulmonary oedema. Consequently, hypotension is a risk during anaesthesia. Careful infusion of IV fluids is important. Limit blood-loss at Caesarean section.

Prevention of pre-eclampsia O10.0/O24.0-3/O99.1/O99.8 + (D68.6/M32.9)

For women at high risk of pre-eclampsia, e.g. pre-eclampsia in a previous pregnancy, chronic hypertension, diabetes, antiphospholipid syndrome or SLE.

From 6 weeks’ gestation onwards, preferably before 16 weeks gestation:

  • Aspirin, oral, 150 mg daily.

LoEI [16]

  • Calcium, oral.
    • For high-risk patients: Calcium carbonate, oral, 500 mg 12 hourly (equivalent to 1 g elemental calcium daily).
    • Although the benefit is greatest in high-risk women, consider use of this agent in all pregnant women.
    • When using iron together with calcium supplementation, ensure that iron and calcium are taken at least 4 hours apart from one another.

LoEI [17]

Prevention of eclampsia

To prevent eclamptic seizures, magnesium sulfate is recommended for patients with severe features. In some cases this allows for delivery to be delayed to improve neonatal outcome. When used for prevention of eclampsia, magnesium sulfate is administered for 24 hours, and then stopped. The same dose regimens are used as for eclampsia. Women with severe features should be managed under specialist care.