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

BACKGROUND AND OBJECTIVE: 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. METHODOLOGY: 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. RESULTS: 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). CONCLUSION: 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.

Duke Scholars

Author An-Kwok Ian Wong Medicine, Pulmonary, Allergy, and Critical Care Medicine