Association of magnesium abnormalities at intensive care unit admission with kidney outcomes and mortality: a prospective cohort study.

Background: Magnesium abnormalities have been associated with adverse kidney outcomes and mortality in critically ill patients, however, this association remains inconsistent. This study aimed to investigate the association of magnesium abnormalities at intensive care unit (ICU) admission with kidney outcomes (i.e., acute kidney injury (AKI) and kidney function recovery) and mortality risk in a large cohort of critically ill patients.

Methods: A prospective cohort study was conducted by collecting data from three ICUs in Brazil. The ICU admission serum magnesium level was used to define hypomagnesemia (< 1.60 mg/dL) and hypermagnesemia (> 2.40 mg/dL). The Kidney Disease Improving Global Outcomes AKI Guideline was used to define AKI based on serum creatinine levels. Kidney function recovery was defined as full recovery, partial recovery, and non-recovery at ICU discharge. Mortality was screened up to 28 days during ICU stay.

Results: A total of 7,042 patients was analyzed, hypomagnesemia was found in 18.4% (n = 1,299) and hypermagnesemia in 4.4% (n = 311). Patients with hypomagnesemia were 25% more likely to develop AKI after adjustment for confounding variables (OR = 1.25; 95% CI 1.08-1.46). No significant association was found for hypermagnesemia and AKI (OR = 1.18; 95% CI 0.89-1.57). Kidney function recovery was similar among groups but hypermagnesemia had lower non-recovery rates. Both hypomagnesemia and hypermagnesemia were associated with 65 and 52% higher mortality risk after adjustments for confounders, respectively (HR = 1.65; 95% CI 1.32-2.06 and 1.52; 95% CI 1.01-2.29).

Conclusions: Hypomagnesemia, but not hypermagnesemia, at ICU admission was associated with AKI development. On the other hand, both hypomagnesemia and hypermagnesemia were associated with higher mortality risks.