DALLAS—Low and high serum potassium levels are associated with increased mortality risk in patients with chronic kidney disease (CKD), researchers reported at the National Kidney Foundation’s 2015 Spring Clinical Meetings.

In a study of 42,912 patients with stage 3 or 4 CKD, Georges N. Nakhoul, MD, and colleagues at Cleveland Clinic found that hypokalemia (potassium levels below 3.5 mmol/L) and hyperkalemia (potassium levels 5.5 mmol/L or above) were associated with a 26% and 22% increased risk of death, respectively, compared with a potassium level of 4.0 – 4.9 mmol/L (reference). The investigators found no association between serum potassium and risk of end-stage renal disease.

The study population, which had a mean age of 72 years, was 54% female and 13% African American. Dr. Nakhoul’s group obtained data from their institution’s electronic health record-based CKD registry.

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The researchers noted that hypokalemia and hyperkalemia have been linked to increased mortality usually as a consequence of the arrhythmogenic effects of potassium.

“The results are not surprising for mortality,” commented Csaba P. Kovesdy, MD, who has conducted research on potassium levels and mortality in patients with renal disease but was not involved in the new study. “But I was surprised that [the researchers] did not find associations with ESRD.”

The study has the advantage of a moderately large study sample and fairly good representation of confounders, said Dr. Kovesdy, Director of the Clinical Outcomes and Clinical Trials Program in the Division of Nephrology at the University of Tennessee Health Science Center in Memphis and Nephrology Section Chief at the Memphis VA Medical Center. 

The study, however, relied on data from a single center, which limits interpretation of study findings. Another limitation is the use of a single baseline serum potassium value, which may or may not represent long-term potassium levels and may not be the best way to evaluate the effects on mortality.

Both higher and lower potassium are known to increase mortality through arrhythmias, for which short-term changes in potassium are most relevant, he pointed out.