Jersey City Medical Center Jersey City, NJ, United States
Objective: Standard management of preeclampsia with severe features includes the administration of Magnesium Sulfate (Mg) for the prevention of eclamptic seizures. Most institutions employ a protocol that includes an intravenous loading dose of 4-6 g followed by continuous infusion of 2g/hour. The purpose of this study was to test the hypothesis that maternal serum concentration of Mg is inversely correlated with maternal weight.
Study Design: This retrospective cohort study included women who received I/V Mg for preeclampsia between January 2017 and January 2022 and had a 6-hour Mg serum level determined before delivery. Patients were identified by the hospital pharmacy and their medical records were reviewed. Data reviewed included age, gestational age at presentation, blood pressure on admission, weight (kg), and Mg concentrations. Statistical analysis involved t-test, Pearson correlation, and linear and multiple regression.
Results: 1036 records were reviewed, of these, 56 (5.4%) patients received at least 6 hours of Mg prior to delivery and had a 6-hour determination of Mg level. Mean (+SD) Mg level was 5.11+0.94 mg/dL. Maternal Mg level was inversely correlated with maternal weight (r=0.385; p=0.0034). Multiple regression adjusting for gestational age, systolic, and diastolic blood pressures did not alter this result (p=0.0184). Nineteen of the 56 patients (34%) had a Mg level < 4.8 mg/dL, considered sub-therapeutic. Mean weight of patients with sub-therapeutic and therapeutic Mg levels were 79.64+16.33 Kg vs. 89.45+18.99 Kg, respectively (p=0.025).
Conclusion: Antepartum Mg concentration is inversely correlated with maternal weight. Loading and maintenance doses of Mg may need to be adjusted based on maternal weight.
