From the Guidelines
This patient with preeclampsia with severe features at 37 weeks gestation should receive magnesium sulfate for seizure prophylaxis, antihypertensive therapy, and intrapartum antibiotic prophylaxis for group B Streptococcus.
Management of Preeclampsia
The patient's blood pressure is 184/106 mm Hg, which is considered severe hypertension and requires urgent treatment in a monitored setting 1.
- Magnesium sulfate should be administered as a 4-6 gram IV loading dose over 20-30 minutes, followed by a maintenance infusion of 1-2 grams per hour until 24 hours postpartum.
- Blood pressure should be controlled with IV labetalol (20-40 mg initially, then doubling the dose every 10 minutes if needed, up to 220 mg) or IV hydralazine (5-10 mg every 20-30 minutes) to maintain blood pressure below 160/110 mm Hg 1.
- For GBS prophylaxis, penicillin G 5 million units IV initially, then 2.5-3 million units IV every 4 hours until delivery is recommended (or ampicillin 2 g IV initially, then 1 g IV every 4 hours).
Considerations for Myasthenia Gravis
The patient's myasthenia gravis requires careful monitoring as magnesium sulfate can exacerbate muscle weakness 1.
Delivery and Monitoring
Delivery is the definitive treatment for preeclampsia, and induction should proceed with oxytocin. Close maternal monitoring for worsening preeclampsia symptoms and fetal monitoring are essential throughout labor and delivery 1.
From the Research
Patient Evaluation and Management
- The patient is a 43-year-old primigravida at 37 weeks gestation with a severe headache, dark spots in her vision, and irregular, nonpainful contractions, diagnosed with preeclampsia with severe features.
- The patient's blood pressure is 184/106 mm Hg, and she has a history of myasthenia gravis, taking pyridostigmine.
- The patient is admitted for induction of labor due to preeclampsia with severe features.
Magnesium Sulfate Treatment
- Magnesium sulfate is the drug of choice for prevention of seizures in pre-eclamptic women, as shown in studies 2, 3.
- A study published in 2017 found that a single dose of magnesium sulfate is equally effective as a standard dose regimen in terms of seizure prophylaxis in severe pre-eclamptic women, with added advantages of reduced maternal toxicity and better neonatal outcome 2.
- Another study published in 1996 found that magnesium sulfate is a significantly better drug than either diazepam or phenytoin for preventing recurrent seizures in eclamptic patients 3.
Duration of Postpartum Magnesium Sulfate
- A systematic review and meta-analysis published in 2022 found that the duration of postpartum magnesium sulfate for seizure prophylaxis in women with preeclampsia does not affect the incidence of seizures postpartum, but women who received <24 hours of postpartum magnesium sulfate had a significantly faster time to ambulation postpartum and shorter durations of indwelling urinary catheter placement 4.
- However, the review suggests that continued use of 24 hours of postpartum magnesium sulfate for seizure prophylaxis is still supported, as eclampsia is a rare occurrence and the two cases of eclampsia reported occurred in the group of women who received <24 hours of postpartum magnesium sulfate.
Blood Loss at Cesarean Delivery
- A study published in 2016 found that magnesium sulfate does not appear to affect blood loss intrapartum and postpartum in women with preeclampsia, and therefore, should be continued during cesarean delivery, given the benefit of seizure prophylaxis without any increased risk of hemorrhage 5.
Mechanism of Action of Magnesium Sulfate
- A study published in 2014 found that magnesium sulfate treatment reverses seizure susceptibility and decreases neuroinflammation in a rat model of severe preeclampsia, suggesting that reducing neuroinflammation may be one mechanism by which magnesium sulfate prevents eclampsia during severe preeclampsia 6.