Background/aims

Abnormal serum potassium is associated with higher mortality in dialysis patients, but its impact on outcomes in predialysis chronic kidney disease (CKD) is less clear. Furthermore, blacks with normal kidney function have lower urinary potassium excretion, but it is unclear if such differences have a bearing on race-associated outcomes in CKD.

Methods

We studied predialysis mortality and slopes of estimated glomerular filtration rate, eGFR) associated with serum potassium in 1,227 males with CKD. Mortality was examined in time-dependent Cox models, and slopes of eGFR in linear mixed effects models with adjustments for case mix and laboratory values.

Results

Both hypo- and hyperkalemia were associated with mortality overall and in 933 white patients, but in 294 blacks hypokalemia was a stronger death predictor. Hypokalemia was associated with loss of kidney function independent of race: a 1 mEq/l lower potassium was associated with an adjusted difference in slopes of eGFR of -0.13 ml/min/1.73 m(2)/year (95% CI: -0.20 to -0.07), p < 0.001.

Conclusion

Hypo- and hyperkalemia are associated with higher mortality in CKD patients. Blacks appear to better tolerate higher potassium than whites. Hypokalemia is associated with faster CKD progression independent of race. Hyperkalemia management may warrant race-specific consideration, and hypokalemia correction may slow CKD progression.