What is the recommended management of postpartum preeclampsia using Lasix (furosemide) and potassium supplementation?

Management of Postpartum Preeclampsia with Furosemide and Potassium

For severe postpartum preeclampsia, furosemide 20-40 mg daily for 5 days with potassium supplementation accelerates blood pressure normalization and reduces antihypertensive requirements, but should NOT be used in mild preeclampsia or when uteroplacental perfusion is already compromised. 1, 2

When to Use Furosemide

Furosemide is indicated specifically for severe postpartum preeclampsia only after:

• Spontaneous diuresis has begun 1
• Magnesium sulfate has been discontinued 1
• Blood pressure remains ≥160/110 mmHg despite initial management 3, 4

The evidence shows furosemide benefits only patients with severe preeclampsia, not mild or superimposed preeclampsia. 1

Dosing Protocol

Furosemide regimen:

• 20-40 mg orally once daily for 5 days 1, 2, 5
• Must be accompanied by oral potassium supplementation 1

The higher dose (40 mg) demonstrated superior blood pressure reduction in the most recent trial, lowering mean systolic BP on days 1 and 5, and diastolic BP on days 1,2, and 5. 2

Expected Benefits

In severe postpartum preeclampsia, furosemide produces:

• Lower systolic BP by postpartum day 2 (142 vs 153 mmHg in controls) 1
• Reduced need for antihypertensive therapy at discharge (6% vs 26%) 1
• Fewer severe hypertensive episodes on days 2 and 5 2
• Shorter time to blood pressure control 2
• Decreased requirement for additional antihypertensives (8% vs 26%) 5

Critical Contraindications

Do NOT use furosemide when:

• Oliguria is present (diuretics worsen uteroplacental perfusion when blood volume is already reduced) 6
• Patient has renal disease, acute kidney injury, placental abruption, sepsis, or postpartum hemorrhage 4
• Mild preeclampsia only (no demonstrated benefit) 1
• Patient is breastfeeding and milk production is a concern (diuretics may reduce lactation) 7

A case report documented severe harm from furosemide given for oliguria in preeclampsia, where the already-decreased blood volume and uteroplacental flow were further compromised. 6

First-Line Antihypertensive Management

Before or concurrent with furosemide, use standard antihypertensives:

• Oral: labetalol, nifedipine, or methyldopa 3, 7
• IV for severe hypertension: labetalol, hydralazine, or nicardipine 3, 7
• Target: systolic <160 mmHg and diastolic <110 mmHg 7, 3, 4

Methyldopa remains widely recommended but use cautiously in women at risk for postpartum depression. 7

Monitoring Requirements

Blood pressure monitoring:

• Every 4-6 hours while awake for minimum 3 days postpartum 3, 4
• Continue antihypertensives and taper slowly only after days 3-6 3

Laboratory monitoring:

• Repeat hemoglobin, platelets, creatinine, and liver transaminases daily until stable 3, 4
• Assess for headache, visual disturbances, right upper quadrant pain 3

Discharge and Follow-up

Most women can be discharged by day 5 postpartum if:

• Blood pressure is controlled 3
• Home BP monitoring is available 3

Mandatory follow-up:

• Review at 6 weeks postpartum to confirm normalization of BP, urinalysis, and labs 7, 3
• Refer to specialist if hypertension or proteinuria persists at 6 weeks 7, 3, 4
• Counsel about 15% recurrence risk in future pregnancies and increased lifetime cardiovascular disease risk 3, 4

Common Pitfalls

The historical controversy about diuretics in pregnancy stems from concerns about reducing plasma volume expansion and promoting preeclampsia development. 7 However, this applies to antepartum use—postpartum physiology is different, with fluid mobilization from extravascular to intravascular space increasing central venous pressure. 5 In this postpartum context, diuretics address volume overload rather than depleting an already-compromised circulation. 5

The key distinction: Furosemide is beneficial postpartum in severe preeclampsia with adequate diuresis, but harmful when given for oliguria or reduced perfusion. 6, 1