Electrolyte disturbance phenotypes and adverse outcomes in the intensive care unit: The role of magnesium and potassium abnormalities.

BACKGROUND

Magnesium and potassium disturbances are common in critically ill patients, but the prognostic value of their co-occurrence is poorly defined.

OBJECTIVE

To evaluate the association of combined magnesium-potassium phenotypes at intensive care unit (ICU) admission with 30-day in-hospital mortality, acute kidney injury (AKI), and invasive mechanical ventilation.

METHODS

This retrospective cohort included 9462 adults admitted to the ICU of a tertiary hospital in Jordan (2012-2022) with admission magnesium and potassium, classified into nine phenotypes. Mortality was analyzed by Cox regression, censoring patients discharged alive at discharge, and AKI and ventilation by logistic regression, adjusted for age, sex, and modified APACHE II score.

RESULTS

Thirty-day mortality was 30.6%, ranging from 25.0% with normal magnesium and potassium to 63.6% with combined hypermagnesemia-hyperkalemia. The combined phenotype had the highest adjusted hazard of death (HR 3.01, 95% CI 2.60-3.49), with positive additive interaction (relative excess risk due to interaction 0.76, 95% CI 0.29-1.23). Isolated hyperkalemia (HR 1.63, 95% CI 1.46-1.82) and isolated hypermagnesemia (HR 1.62, 95% CI 1.42-1.86) were also associated with mortality. The combined phenotype was associated with AKI (aOR 2.66, 95% CI 2.09-3.38) and ventilation (aOR 1.51, 95% CI 1.17-1.94). Modeled continuously, potassium showed a U-shaped and magnesium a J-shaped association with mortality.

CONCLUSION

Co-occurring hypermagnesemia and hyperkalemia at ICU admission identify a high-risk phenotype. Because both are measured routinely, this combination may serve as a simple marker for early risk stratification.