Impact of admission serum potassium on mortality in patients with chronic kidney disease and cardiovascular disease

Background: Little is known about the effect of admission potassium (K) on risk of in-hospital mortality in chronic kidney disease (CKD) and cardiovascular disease (CVD) patients. Aim: The aim of this study was to assess the relationship between admission serum K and in-hospital mortality in all hospitalized patients stratified by CKD and/or CVD status. Design and Methods: All adult hospitalized patients who had admission serum K between years 2011 and 2013 were enrolled. Admission serum K was categorized into seven groups (<3.0, 3.0-3.5, 3.5-4.0, 4.0-4.5, 4.5-5.0, 5.0-5.5 and >= 5.5 mEq/L). The odds ratio (OR) of in-hospital mortality by admission serum K, using K 4.0-4.5 mEq/L as the reference group, was obtained by logistic regression analysis. Results: 73,983 patients were studied. The lowest incidence of in-hospital mortality was associated with serum K within 4.0-4.5 mEq/L. A U-shaped curve emerged demonstrating higher in-hospital mortality associated with both serum K<4.0 and >4.5 mEq/L. After adjusting for potential confounders, both serum K<4.0 mEq/L and >5.0 mEq/L were associated with increased in-hospital mortality with ORs of 3.26 (95% CI 2.03-4.98), 2.40 (95% CI 1.89-3.04), 1.38 (95% CI 1.15-1.66), 1.89 (95% CI 1.49-2.38) and 3.62 (95% CI 2.73-4.76) when serum K were within <3.0, 3.0-3.5, 3.5-4.0, 5.0-5.5, and >= 5.5 mEq/L, respectively. In CVD patients, the highest in-hospital mortality was associated with serum K<3.0 mEq/L (OR 1.70, 95% CI 1.31-2.18). In CKD patients, the highest in-hospital mortality was associated with serum K >= 5.5 mEq/L (OR 3.26, 95% CI 2.14-4.90). Conclusion: Admission serum K<4.0 mEq/L and >5.0 mEq/L were associated with increased in-hospital mortality. The mortality risk among patients with various admission potassium levels was affected by CKD and/or CVD status.