From the Guidelines
Magnesium sulfate should be restarted in postpartum patients for at least 24 hours after delivery, as this approach is reasonable until further studies confirm alternative findings in other populations. The decision to restart magnesium in postpartum patients is guided by the need to prevent eclampsia, which can occur postpartum, and the known benefits of magnesium sulfate in this context 1.
Indications for Restarting Magnesium
The indications for restarting magnesium in postpartum patients include:
- New-onset severe hypertension (systolic BP ≥160 mmHg or diastolic BP ≥110 mmHg)
- New neurological symptoms (severe headache, visual disturbances, altered mental status)
- Seizures
- HELLP syndrome These conditions suggest a high risk of eclampsia or severe preeclampsia, where magnesium sulfate has been shown to be beneficial in preventing seizures and improving outcomes 2.
Administration and Monitoring
The standard regimen for magnesium sulfate administration consists of a 4-6 gram IV loading dose administered over 20-30 minutes, followed by a continuous infusion of 1-2 grams per hour. It is crucial to monitor for magnesium toxicity by checking deep tendon reflexes, respiratory rate, and urine output. Serum magnesium levels should be maintained between 4-7 mEq/L for seizure prophylaxis. Renal function should be assessed before restarting magnesium, as impaired kidney function increases the risk of toxicity and may require dose adjustment or more frequent monitoring.
Considerations
Each unit should develop their own protocols for postpartum magnesium use, taking into consideration the incidence of eclampsia postpartum and the benefits of magnesium sulfate in preventing this condition 1. The approach to restarting magnesium should be based on the most recent and highest quality evidence available, prioritizing the prevention of morbidity, mortality, and improvement in quality of life for postpartum patients.
From the FDA Drug Label
Magnesium Sulfate Injection, USP is suitable for replacement therapy in magnesium deficiency, especially in acute hypomagnesemia accompanied by signs of tetany similar to those observed in hypocalcemia.
Magnesium sulfate injection should not be given unless hypomagnesemia has been confirmed and the serum concentration of magnesium is monitored.
The normal serum level is 1.5 to 2. 5 mEq/L.
The indications for restarting magnesium in a postpartum patient are:
- Hypomagnesemia: Magnesium sulfate can be restarted if the patient has a confirmed magnesium deficiency, especially if they show signs of tetany.
- Serum magnesium level: The decision to restart magnesium should be based on the patient's serum magnesium level, which should be monitored regularly.
- Normal serum level: The normal serum magnesium level is between 1.5 to 2.5 mEq/L 3, 4.
Note: The FDA drug label does not provide specific guidance on restarting magnesium in postpartum patients, but it does provide information on the indications for magnesium sulfate therapy in general.
From the Research
Indications for Restarting Magnesium in Postpartum Patients
The decision to restart magnesium in postpartum patients depends on various factors, including the presence of severe hypertension, neurologic symptoms, and the risk of eclamptic seizures.
- Patients with chronic hypertension complicated by superimposed pre-eclampsia are at higher risk for the need of reinstitution of seizure prophylaxis postpartum 5.
- Patients delivered prior to 35 weeks' gestation and patients requiring a longer initial magnesium prophylaxis are also at higher risk for the need of reinstitution of seizure prophylaxis postpartum 5.
- Eclampsia that occurs more than 48 hours after delivery is rare, but it is most commonly preceded by headaches or other cerebral symptoms, and magnesium sulfate therapy may be reserved for the subset of patients with neurologic symptoms who may be at highest risk for an eclamptic seizure 6.
- Magnesium sulfate has been shown to reduce the risk of eclampsia and recurrent seizures in eclamptic patients, and it is now the drug of choice for treating eclamptic patients 7, 8.
Patient Profile Predictive of Need for Additional Therapy
Certain patient profiles may be predictive of the need for additional magnesium sulfate therapy, including:
- Chronic hypertension complicated by superimposed pre-eclampsia 5
- Gestational age less than 35 weeks 5
- Longer initial magnesium prophylaxis 5
- Presence of neurologic symptoms, such as headaches or other cerebral symptoms 6
Benefits and Risks of Magnesium Sulfate Therapy
Magnesium sulfate therapy has several benefits, including the reduction of eclampsia and recurrent seizures in eclamptic patients 7, 8. However, it also has several risks, including: