PRES vs Eclampsia: Immediate Management
Critical Distinction in Management Approach
Both PRES and eclampsia in pregnancy require identical immediate management: magnesium sulfate for seizure control, aggressive blood pressure reduction to <160/105 mmHg, and delivery after maternal stabilization. 1, 2, 3
The key clinical reality is that PRES occurs in 97.9-100% of eclampsia cases, making them overlapping rather than distinct entities requiring different treatment approaches. 4, 5
Immediate Seizure Management
First-Line Anticonvulsant Therapy
Administer magnesium sulfate immediately as a 4-6 gram IV loading dose over 5-15 minutes, followed by continuous infusion of 1-2 g/hour. 1, 2, 3
Magnesium sulfate is superior to phenytoin and diazepam for both stopping active seizures and preventing recurrence in eclampsia/PRES. 1
Continue magnesium sulfate for 24 hours postpartum or until 24 hours after the last seizure. 1, 2, 3
Alternative loading regimen if IV access is limited: 4g IV combined with 10g IM (5g in each buttock) for total 14g loading dose. 3
Recurrent Seizure Protocol
If seizures recur despite initial loading dose, administer an additional 2 grams magnesium sulfate IV over 5 minutes. 2
In the rare case of magnesium toxicity with ongoing seizures (as documented in case reports), lorazepam may be required as rescue therapy. 6
Concurrent Blood Pressure Control
Target Blood Pressure
Maintain blood pressure <160/105 mmHg to prevent maternal complications while avoiding excessive reduction that compromises uteroplacental perfusion. 7, 1, 2, 3
Blood pressure ≥160/110 mmHg lasting >15 minutes requires immediate antihypertensive treatment. 2
First-Line IV Antihypertensives
Labetalol: Initial 20mg IV bolus, then 40mg after 10 minutes, followed by 80mg every 10 minutes to maximum cumulative dose of 220-800mg in 24 hours. 2, 3
Nicardipine: Start at 5mg/hour, increase by 2.5mg/hour every 5-15 minutes to maximum 15mg/hour. 7, 2, 3
Second-Line and Oral Options
IV hydralazine is a second-line option when labetalol or nicardipine are unavailable or contraindicated. 7, 2
Oral nifedipine (extended-release) can be used for chronic BP control but avoid concurrent IV administration with magnesium sulfate. 7, 1, 2
Critical Drug Interactions and Contraindications
Absolute Contraindications
NEVER combine magnesium sulfate with IV or sublingual nifedipine - this causes severe myocardial depression and hypotension from synergistic effects. 1, 2, 3
Avoid diuretics as plasma volume is already reduced in preeclampsia/eclampsia. 7, 2, 3
Do not use methyldopa for urgent blood pressure reduction in eclampsia - it is too slow-acting. 2
Avoid sodium nitroprusside due to risk of fetal cyanide toxicity. 3
Monitoring for Magnesium Toxicity
Assess deep tendon reflexes (loss indicates toxicity), respiratory rate (depression <12/min is concerning), and urine output (maintain >100mL over 4 hours). 3
Signs of toxicity include loss of patellar reflexes, respiratory depression, cardiac conduction abnormalities, and cardiac arrest. 3
Keep injectable calcium salt immediately available to counteract magnesium toxicity. 3
Maternal Monitoring Protocol
Continuous Assessment
Monitor blood pressure continuously during acute phase, then every 15 minutes until stable. 3
Perform neurologic checks including assessment for headache, visual disturbances, altered mental status, and clonus. 7, 3
Maintain continuous fetal heart rate monitoring. 3
Laboratory Surveillance
Obtain labs twice weekly (or more frequently with clinical changes): hemoglobin, platelet count, liver transaminases, creatinine, and uric acid. 7, 3
Monitor for HELLP syndrome development (hemolysis, elevated liver enzymes, low platelets). 8
Delivery Planning
Stabilization Before Delivery
Stabilize the mother FIRST with magnesium sulfate and blood pressure control before proceeding to delivery. 1, 3
The objective is to achieve BP control within 150-180 minutes. 7
Indications for Immediate Delivery
Inability to control blood pressure despite ≥3 classes of antihypertensives in appropriate doses. 7, 3
Progressive deterioration in liver function, creatinine, hemolysis, or platelet count. 7, 3
Ongoing neurological features including severe intractable headache, repeated visual scotomata, or recurrent eclamptic seizures. 7, 3
Gestational age ≥37 weeks with any preeclampsia/eclampsia. 7, 3
Delivery Method
Vaginal delivery is preferred unless cesarean is indicated for standard obstetric reasons. 3
Administer antenatal corticosteroids if gestational age ≤34 weeks to accelerate fetal lung maturation. 3
Neuroimaging Considerations
When to Image
While not required for immediate management, MRI without contrast is the most sensitive modality (87.2% detection rate) for confirming PRES if diagnosis is uncertain. 4
PRES typically shows vasogenic edema in parietal (78.3%), occipital (76.1%), frontal (63%), and temporal (28.3%) regions. 4, 5
Clinical Implications
The presence of PRES does not change acute management - treatment remains identical to eclampsia management. 9, 4, 5
Neuroimaging abnormalities are typically reversible with appropriate blood pressure control and seizure management. 9, 5
Common Pitfalls to Avoid
Do not delay magnesium sulfate while waiting for neuroimaging - clinical diagnosis of eclampsia is sufficient to initiate treatment. 1, 2
Do not use excessive labetalol doses (>800mg/24 hours) as this increases risk of fetal bradycardia. 1
Do not restrict activity or enforce bed rest in mild preeclampsia - this is outdated and not beneficial. 7
Do not use plasma volume expansion routinely in preeclampsia/eclampsia. 7
Do not attempt to distinguish "mild" versus "severe" preeclampsia clinically as all cases may become emergencies rapidly. 7
Postpartum Management
Continue magnesium sulfate for 24 hours after delivery or last seizure. 3
Continue antihypertensive therapy during labor and postpartum period as needed. 3
Check blood pressure and urine at 6 weeks postpartum, and assess for secondary causes of hypertension in women under 40 with persistent hypertension. 3