The optimal range of plasma potassium varies by stage of chronic kidney disease (CKD), a new study suggests.

In a paper published in Nephrology Dialysis Transplantation, investigators wrote that “although our study supports the view that hyperkalaemia is better tolerated in CKD, it challenges the current use of a single clinical K+ range for all patients.”

Juan-Jesús Carrero, PhD, of Karolinska Institutet in Sweden, and his team investigated plasma potassium levels in 831,760 participants in the Stockholm CREAtinine Measurements (SCREAM) project. Of these, 8.5% had stage 3 CKD and 1.1% stage 4 to 5 CKD. Results showed that plasma potassium increased with CKD stage from a median 3.98 mmol/L in those with an estimated glomerular filtration rate (eGFR) more than 90 mL/min/1.73 m2 to 4.43 mmol/L for those with an eGFR less than 15 mL/min/1.73 m2.

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As plasma potassium increased, mortality risk dipped and then rose again in a U-shaped pattern. Each group exhibited a different safe range of plasma potassium. The optimal range associated with 90-day mortality risk was 3.45 to 4.94 mmol/L in patients with an eGFR greater than 60 mL/min/1.73 m2, but it widened in patients with CKD: 3.36 to 5.18 mmol/L for stage 3 and 3.26 to 5.53 mmol/L for stage 4 to 5.

Patients with advanced CKD may develop greater tolerance to potassium retention, the authors stated. They added that disease-specific potassium ranges may be needed so clinicians can know the exact point at which alternate therapy should be considered.

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Gasparini A, Evans M, Barany P, et al. Plasma potassium ranges associated with mortality across stages of chronic kidney disease: the Stockholm CREAtinine Measurements (SCREAM) project. Nephrol Dial Transplant 2018;1–8. DOI: 10.1093/ndt/gfy249