Why a Person Would Receive Magnesium Sulfate and 25% Albumin IV
A pregnant woman with severe pre-eclampsia or eclampsia receives magnesium sulfate to prevent and control seizures (the most effective anticonvulsant for this indication), while 25% albumin is administered to manage severe hypoalbuminemia and intravascular volume depletion that can occur with capillary leak syndrome in severe pre-eclampsia. 1
Magnesium Sulfate: Primary Seizure Prevention
Core Indication
- Magnesium sulfate is the gold standard for preventing eclamptic seizures, approximately halving the seizure rate in women with pre-eclampsia and demonstrating superior efficacy compared to phenytoin and diazepam. 1, 2
- The drug is specifically indicated for women with severe pre-eclampsia (BP ≥160/110 mmHg with significant proteinuria ≥3+) or moderate hypertension (BP ≥150/100 mmHg) with at least 2+ proteinuria plus signs of imminent eclampsia (headache, visual disturbances, hyperreflexia, clonus). 1, 3
Why Not Other Anticonvulsants?
- Benzodiazepines like diazepam carry significant risks of respiratory depression in both mother and neonate, making them unsuitable for peripartum use. 1
- Phenytoin has been proven inferior to magnesium sulfate in multiple randomized controlled trials involving over 4,000 women. 1
Clinical Monitoring Requirements
- Monitor clinically rather than with routine serum levels: check patellar reflexes (lost at 3.5-5 mmol/L), respiratory rate (paralysis occurs at 5-6.5 mmol/L), and urine output (maintain ≥30 mL/hour). 1, 4
- Serum magnesium levels should only be checked in specific high-risk situations: renal impairment, oliguria (<30 mL/hour), loss of patellar reflexes, or respiratory rate <12 breaths/minute. 1
25% Albumin: Managing Capillary Leak and Hypovolemia
Pathophysiology in Severe Pre-eclampsia
- Severe pre-eclampsia causes endothelial dysfunction leading to capillary leak syndrome, resulting in intravascular volume depletion despite total body fluid overload (third-spacing). 1
- This creates a paradoxical situation where the patient is simultaneously hypovolemic (intravascularly) and edematous (extravascularly).
Albumin Administration Rationale
- 25% albumin (hyperoncotic solution) draws fluid from the extravascular space back into the intravascular compartment, improving effective circulating volume and organ perfusion.
- This is particularly critical when the patient develops oliguria or acute kidney injury, which increases magnesium toxicity risk since magnesium is renally excreted. 1, 4
- Albumin helps maintain adequate intravascular volume while avoiding excessive crystalloid administration that would worsen pulmonary edema risk.
Critical Safety Considerations
Fluid Management Balance
- Total fluid intake must be limited to 60-80 mL/hour to prevent pulmonary edema, as pre-eclamptic women have increased capillary permeability. 1, 3, 2
- The goal is euvolemia: avoiding both "running the patient dry" (which worsens acute kidney injury and magnesium toxicity) and fluid overload (which causes pulmonary edema). 2
Dangerous Drug Interactions
- Never combine magnesium sulfate with calcium channel blockers (especially IV or sublingual nifedipine), as this causes severe myocardial depression and precipitous hypotension. 1, 3, 2
- If blood pressure control is needed, use labetalol or nicardipine as first-line IV antihypertensives instead. 3
Magnesium Toxicity Management
- Iatrogenic magnesium overdose is possible, particularly if the woman becomes oliguric. 5
- Empirical calcium gluconate administration may be lifesaving if toxicity develops (cardiac arrest can occur at magnesium levels >12.5 mmol/L). 5, 4
- The overall rate of severe adverse effects is low (respiratory depression 1.3%, absent reflexes 1.6%) when properly monitored. 6
Duration of Therapy
- Continue magnesium sulfate for 24 hours postpartum in most cases, as pre-eclampsia may worsen or appear de novo between days 3-6 postpartum. 1, 2
- Maximum duration should not exceed 5-7 days, as prolonged administration beyond this can cause fetal abnormalities. 2