Quantifying the Serum Magnesium Response and Predictors of Response Following Intravenous Magnesium Replacement in...

Intravenous magnesium is commonly used in critically ill patients; however, data on the serum level response following its administration are limited. This study aimed to evaluate serum magnesium changes after administration of intravenous magnesium sulfate (IV-MgSO₄) and identify predictors of a greater response among critically ill patients.

This retrospective multicenter study included adult critically ill patients from the Medical Information Mart for Intensive Care IV and eICU databases. Patients were included if they received IV-MgSO₄ and had serum magnesium measured within 36 h before and after administration. Patients receiving renal replacement therapy, total parenteral nutrition, magnesium-containing intravenous fluids, or oral magnesium supplementation were excluded. Linear regression analyses were performed to identify predictors of greater magnesium response.

The study included 25,637 patients who received 54,556 doses of IV-MgSO₄. The mean age was 62.8 ± 16.5 Standard deviation years, and 13,180 (51.4%) were females. The most common intensive care unit admission diagnoses were cardiovascular (n = 7399; 28.9%) and respiratory (n = 4245; 16.6%). Baseline magnesium levels were normal in 39,149 (71.8%) episodes, mild-to-moderate hypomagnesemia in 13,588 (24.9%), and severe hypomagnesemia in 1819 (3.3%). Median serum magnesium increased by 0.15 mg/dL (interquartile range (IQR) 0.05-0.25) per 1 g of IV-MgSO₄ administered, and the greatest increase was observed in patients with severe hypomagnesemia (median [IQR]: 0.25 mg/dL [0.10-0.50]), followed by mild-to-moderate hypomagnesemia (median [IQR]: 0.22 mg/dL [0.10-0.40]). Predictors of greater response to IV-MgSO₄ were lower initial magnesium (β = 0.2035; 95% confidence interval (CI): 0.193 to 0.214; p < 0.001) and reduced renal function (β = 0.2557; 95% CI: 0.212 to 0.300; p < 0.001).

Among a large cohort of critically ill patients, 1 g of IV-MgSO₄ was associated with a median serum magnesium increase of 0.15 mg/dL. Lower initial magnesium and reduced renal function were predictors of greater serum magnesium increase with intravenous replacement.