Association between serum potassium and 28-day mortality in elderly patients with sepsis: a multicenter cohort study

While dyskalemia is known to affect outcomes in critically ill patients, its specific impact on elderly septic patients remains unclear. Previous studies in general intensive care unit (ICU) populations have shown a U-shaped relationship between serum potassium and mortality, but this pattern may differ in elderly patients with sepsis.

This retrospective cohort study analyzed 12,069 patients aged ≥ 65 years with sepsis from 208 U.S. hospitals using the eICU Collaborative Research Database (2014-2015). Patients were categorized based on their admission serum potassium levels: hypokalemia (< 3.5 mmol/L), normokalemia (3.5-5.0 mmol/L), and hyperkalemia (> 5.0 mmol/L). The primary outcome was 28-day mortality.

Among the cohort (mean age 77.0 [7.6] years; 50.6% women), 16.4% had hypokalemia, 73.2% had normokalemia, and 10.4% had hyperkalemia. In contrast to the U-shaped relationship previously reported in general ICU populations, we observed a significant linear association between serum potassium and 28-day mortality (P = .001). In the unadjusted model, each 1 mmol/L increase in serum potassium was associated with 65% higher odds of mortality (OR, 1.65 [95% CI, 1.54-1.77]). This association was particularly pronounced in patients aged ≥ 80 years (OR, 1.79 [95% CI, 1.59-2.03]). After comprehensive adjustment for confounders, each 1 mmol/L increase in serum potassium was associated with 23% higher odds of mortality (adjusted OR, 1.23 [95% CI, 1.09-1.39]). Compared to normokalemia, hyperkalemia carried significantly higher mortality risk (adjusted OR, 1.45 [95% CI, 1.11-1.88]).

Our findings challenge the established U-shaped paradigm by demonstrating a linear relationship between serum potassium and mortality in elderly septic patients. This suggests that traditional approaches to potassium management may need modification in this vulnerable population, with greater emphasis on preventing hyperkalemia. These results provide a foundation for developing age-specific potassium management strategies in sepsis care.