Management of Severe Preeclampsia with Neurological Symptoms
This patient requires both magnesium sulfate for seizure prophylaxis AND labetalol for blood pressure control (Options B and D together), but if forced to choose a single answer from the options provided, magnesium sulfate (Option D) takes priority given the presence of severe neurological symptoms (headache and visual disturbances) indicating imminent eclampsia.
Rationale for Dual Therapy
Magnesium Sulfate is Mandatory
- Women with preeclampsia who have neurological signs or symptoms (headache, visual disturbances) should receive magnesium sulfate for convulsion prophylaxis 1.
- The presence of headache and visual disturbances indicates imminent eclampsia, which is a strong indication for magnesium sulfate regardless of blood pressure level 2, 3.
- Magnesium sulfate reduces the risk of eclampsia by more than 50% (number needed to treat = 100) and probably reduces maternal death 4.
- The standard loading dose is 4-5g IV over 5 minutes, followed by maintenance infusion of 1-2g/hour for 24 hours after delivery or last seizure 2.
- An alternative regimen is 4g IV combined with 10g IM (5g in each buttock) for settings without infusion pumps 2.
Blood Pressure Management is Also Required
- While the BP of 140/100 mmHg does not meet the threshold for urgent treatment (≥160/110 mmHg), blood pressures consistently at or >140/90 mmHg should be treated to reduce the likelihood of developing severe maternal hypertension and other complications 1.
- Labetalol is the preferred first-line antihypertensive for this clinical scenario 1, 2.
- Labetalol dosing: 20mg IV bolus, then 40mg after 10 minutes, followed by 80mg every 10 minutes to maximum 220mg 1, 2.
- The target is to maintain BP <160/105 mmHg or achieve diastolic BP of 85 mmHg 1.
Why the Other Options Are Inappropriate
Lisinopril (Option A) - Contraindicated
- ACE inhibitors like lisinopril are absolutely contraindicated in pregnancy due to severe fetal toxicity, including renal failure, oligohydramnios, growth restriction, and fetal death 1.
Losartan (Option C) - Contraindicated
- Angiotensin receptor blockers like losartan are absolutely contraindicated in pregnancy for the same reasons as ACE inhibitors 1.
Clinical Monitoring Requirements
Magnesium Toxicity Monitoring
- Monitor deep tendon reflexes (loss occurs at 3.5-5 mmol/L), respiratory rate (paralysis at 5-6.5 mmol/L), and urine output (>100mL over 4 hours) 2, 5, 3.
- Cardiac arrest can occur at concentrations >12.5 mmol/L 5.
- Injectable calcium salt should be immediately available to counteract magnesium toxicity 2.
- Serum magnesium monitoring is not necessary if clinical monitoring is adequate 3.
Blood Pressure Monitoring
- Continuous BP monitoring is essential during antihypertensive administration 2.
- Avoid precipitous drops in BP, as rapid decreases can cause cerebral infarction, optic nerve infarction, and ischemic ECG changes 6.
Important Caveats
Drug Interactions
- Avoid combining magnesium sulfate with calcium channel blockers (like nifedipine) due to risk of severe hypotension 1, 2.
- Short-acting nifedipine should be avoided except when IV access is unavailable 1.
Delivery Planning
- This patient at 37 weeks with severe preeclampsia and neurological symptoms should be delivered after maternal stabilization 1, 2.
- Women with preeclampsia at ≥37 weeks gestation should be delivered 1.
- The presence of severe neurological features (headache, visual disturbances) is an indication for delivery regardless of gestational age 1.
Additional Considerations
- This patient's history of 3 previous cesarean sections places her at high risk for placental abnormalities and should factor into delivery planning 1.
- Continue magnesium sulfate for 24 hours postpartum or after the last seizure 2.
- Laboratory monitoring should include hemoglobin, platelet count, liver enzymes, creatinine, and uric acid at least twice weekly 1, 2.