What laboratory tests and management strategies are used for preeclampsia?

Laboratory Tests and Management Strategies for Preeclampsia

For preeclampsia, essential laboratory monitoring includes complete blood count with platelets, liver function tests, renal function tests, and uric acid levels, with management focused on blood pressure control, magnesium sulfate for seizure prophylaxis, and delivery timing based on disease severity and gestational age. 1

Diagnostic Laboratory Tests

Essential Laboratory Tests

• Complete blood count with platelets - critical for detecting thrombocytopenia (platelets <100,000/mm³), which is a component of HELLP syndrome 1, 2
• Liver function tests - elevated ALT and AST indicate liver involvement and are significantly higher in preeclamptic women 3
• Renal function tests - to assess kidney damage
• Uric acid levels - hyperuricemia indicates kidney dysfunction and predicts preeclampsia severity 3
• Urinary protein assessment - optimally measured using protein/creatinine ratio; ≥30 mg/mmol (0.3 mg/mg) is abnormal 4
• Serum haptoglobin levels - low levels indicate hemolysis in HELLP syndrome 2
• Indirect bilirubin - elevated in HELLP syndrome due to hemolysis 2

Frequency of Monitoring

• Minimum twice weekly blood tests for women with diagnosed preeclampsia 4
• More frequent monitoring may be needed with worsening clinical status

Management Strategies

Blood Pressure Management

Severe Hypertension (>160/110 mmHg)

• Requires urgent treatment in a monitored setting 4
• First-line IV medications:
  • Labetalol
  • Hydralazine
  • Nifedipine (oral) 4, 1

Non-Severe Hypertension (≥140/90 mmHg)

• Target diastolic BP of 85 mmHg (systolic 110-140 mmHg) 4, 1
• First-line oral agents:
  • Methyldopa
  • Labetalol
  • Oxprenolol
  • Nifedipine 4
• Second/third-line agents:
  • Hydralazine
  • Prazosin 4
• Reduce or cease antihypertensives if diastolic BP falls <80 mmHg 4

Seizure Prophylaxis

• Magnesium sulfate for women with preeclampsia who have:
  • Proteinuria and severe hypertension
  • Hypertension with neurological signs/symptoms 4

Magnesium Sulfate Administration

• Monitoring requirements:
  • Presence of patellar reflex (knee jerk)
  • Respiratory rate ≥16 breaths/min
  • Urine output ≥100 mL in preceding 4 hours
  • Serum magnesium levels (therapeutic range: 3-6 mg/100 mL) 5
• Cautions:
  • Dilute 50% solution to 20% or less for IV infusion
  • Administer slowly to avoid hypermagnesemia
  • Have injectable calcium salt immediately available to counteract magnesium toxicity 5

Maternal Monitoring

• Blood pressure - at each antenatal visit
• Proteinuria assessment - repeated if not already present
• Clinical assessment - including checking for clonus
• Laboratory tests - as outlined above 4, 1

Fetal Monitoring

• Initial assessment to confirm fetal well-being
• Continuous fetal heart rate monitoring in patients with preeclampsia
• Ultrasound for:
  • Fetal growth assessment
  • Amniotic fluid volume assessment
  • Doppler studies if growth restriction is suspected 1

Delivery Indications

Deliver women with preeclampsia if:

• Reached 37 weeks' gestation (and zero days)
• Repeated episodes of severe hypertension despite treatment with 3 classes of antihypertensives
• Progressive thrombocytopenia
• Progressively abnormal renal or liver enzyme tests
• Pulmonary edema
• Abnormal neurological features (severe headache, visual scotomata, convulsions)
• Non-reassuring fetal status 4

Special Considerations for HELLP Syndrome

• Diagnosis requires:
  • Hemolysis (peripheral smear examination, elevated indirect bilirubin, or low haptoglobin)
  • Elevated liver enzymes
  • Platelet count <100,000/mm³ 2
• Management:
  • Immediate delivery regardless of gestational age
  • Platelet transfusion if count <50,000/mm³, especially prior to Cesarean section
  • Whole blood or packed red cells if hemoglobin <10 g/dL 1, 2

Postpartum Care

• Continue BP monitoring every 4-6 hours for at least 3 days
• Taper antihypertensive medications slowly after days 3-6
• Follow-up within 1 week if still on antihypertensives at discharge
• Home BP monitoring with proper technique and appropriate cuff size 1

Prevention Strategies

For High-Risk Women

• Low-dose aspirin (81 mg/day):
  • Initiate between 12-16 weeks gestation
  • Continue until delivery
  • Reduces preeclampsia risk by 24% 1

Calcium Supplementation

• 1.0-1.5g elemental calcium daily for women with low calcium intake
• Start at first antenatal contact, ideally before 20 weeks gestation
• Take in divided doses of no more than 500mg per administration 1

Common Pitfalls and Caveats

• Failure to recognize and promptly treat severe hypertension (>160/110 mmHg)
• Inadequate monitoring of magnesium sulfate therapy, which can lead to toxicity
• Delayed delivery when indicated by maternal or fetal status
• Overlooking postpartum preeclampsia, which can develop up to 6 weeks after delivery 6
• Failure to provide appropriate follow-up, as women with history of preeclampsia have increased risks of cardiovascular disease later in life 6