What is the immediate management for Posterior Reversible Encephalopathy Syndrome (PRES) secondary to eclampsia?

Immediate Management of PRES Secondary to Eclampsia

For PRES secondary to eclampsia, immediately administer intravenous magnesium sulfate (4g IV over 5 minutes, then 1g/hour maintenance) combined with antihypertensive therapy targeting blood pressure <160/105 mmHg using IV labetalol or nicardipine as first-line agents, followed by delivery after maternal stabilization. 1, 2

Seizure Control and Neuroprotection

• Magnesium sulfate is the mandatory first-line anticonvulsant for eclampsia-related PRES, administered as 4-5g IV loading dose over 5 minutes, followed by 1-2g/hour continuous IV infusion for 24 hours after the last seizure 2, 3

• Alternative loading regimen: 4g IV combined with 10g IM (5g in each buttock) if IV access is limited 2

• The magnesium infusion should continue for 24 hours postpartum or 24 hours after the last seizure, whichever is later 2

• Monitor for magnesium toxicity by checking patellar reflexes hourly, respiratory rate (must be >12/min), and urine output (>100mL over 4 hours preceding each dose) 2

• Keep injectable calcium gluconate or calcium chloride at bedside to reverse magnesium toxicity if respiratory depression or cardiac conduction abnormalities develop 2

Blood Pressure Management

Target blood pressure should be <160/105 mmHg to prevent further cerebrovascular complications while avoiding precipitous drops that could worsen cerebral perfusion. 1, 2

First-Line IV Antihypertensives:

• Labetalol: Start with 10-20mg IV bolus, then 20-80mg IV every 10-30 minutes up to maximum cumulative dose of 300mg in 24 hours 1

  • Alternative dosing: 20mg initial bolus, then 40mg after 10 minutes, followed by 80mg every 10 minutes to maximum 220mg 2

• Nicardipine: Start at 5mg/hour IV infusion, increase by 2.5mg/hour every 5-15 minutes to maximum 15mg/hour 1, 2

Alternative Agents:

• Urapidil: Bolus 12.5-25mg IV, then maintain at 5-40mg/hour infusion 1, 4

• Oral nifedipine (10-20mg) may be used if IV access is unavailable, but exercise extreme caution when combined with magnesium sulfate due to risk of severe hypotension 1, 4

Critical Monitoring Parameters

• Continuous blood pressure monitoring with automated cuff every 15 minutes during acute phase 2

• Neurological assessment including level of consciousness, visual symptoms, and deep tendon reflexes hourly 2

• Continuous fetal heart rate monitoring if pregnancy ongoing 1, 2

• Laboratory monitoring twice weekly: complete blood count with platelets, liver enzymes (AST, ALT), creatinine, uric acid, and coagulation studies 2

• Strict fluid balance monitoring with urine output measurement—maintain output >100mL per 4 hours but avoid fluid overload as plasma volume is already reduced in eclampsia 1, 2

Delivery Planning

Delivery is the definitive treatment and should occur after maternal stabilization, typically within hours of eclamptic seizure. 1, 2

• Immediate delivery indications include: inability to control blood pressure despite two medications, progressive deterioration in liver function or platelet count, ongoing neurological symptoms, placental abruption, abnormal fetal status, or gestational age ≥37 weeks 2

• Vaginal delivery is preferred unless cesarean section is indicated for obstetric reasons 1, 2

• If gestational age ≤34 weeks and delivery can be safely delayed, administer corticosteroids (betamethasone or dexamethasone per local protocol) for fetal lung maturation 1, 2

Critical Pitfalls to Avoid

• Never use sodium nitroprusside except as absolute last resort for <4 hours, as prolonged use causes fetal cyanide poisoning and increases maternal intracranial pressure, potentially worsening cerebral edema in PRES 1, 4

• Avoid diuretics as they worsen the already reduced plasma volume in eclampsia 1

• Do not combine magnesium sulfate with calcium channel blockers without extreme caution due to risk of profound hypotension 2

• Avoid rapid blood pressure reduction >15-25% of mean arterial pressure in the first hour, as this can precipitate cerebral ischemia and worsen PRES 1, 4

• Do not exceed labetalol cumulative dose of 300mg in 24 hours to prevent fetal bradycardia 4

• Hydralazine should be second-line only due to association with adverse perinatal outcomes and risk of precipitous hypotension causing fetal distress 1, 4, 5

Special Consideration for Pulmonary Edema

If PRES/eclampsia is associated with pulmonary edema (a known complication), use IV nitroglycerin starting at 5mcg/min, gradually increased every 3-5 minutes to maximum 100mcg/min 1

Postpartum Management

• Continue magnesium sulfate for 24 hours after delivery 2

• Continue antihypertensive therapy during labor and postpartum period 2

• Check blood pressure and urine at 6 weeks postpartum 4, 2

• Refer to specialist if hypertension or proteinuria persists at 6 weeks postpartum 4