Low and high potassium levels associated with harm in older people with chronic kidney disease

People with chronic kidney disease (CKD) stages 4 and 5 are prone to serum potassium disturbances that may increase the risk of kidney function decline, particularly in older people who are at higher risk of comorbidities and subsequent polypharmacy. Additionally, both hypokalaemia and hyperkalaemia can cause muscle paralysis and potentially fatal cardiac arrhythmias. 

This prospective, observational cohort study investigated in older people with CKD stage 4–5 the poorly understood relationship between serum potassium and the combined outcome of death or the occurrence of kidney failure requiring kidney replacement therapy (KRT). Participants (n=1714) aged ≥65 years from the EQUAL (European QUALity) study were followed for 8 years after their eGFR first fell to ≤20 mL/min/1.73 m2. Serum potassium was measured every 3–6 months and categorised as: ≤3.5; >3.5–≤4.0;>4.0–≤4.5; >4.5–≤5.0 (reference); >5.0–≤5.5; >5.5–≤6.0 mmol/L; and >6.0 mmol/L. 

At baseline, 66% of participants were men, 42% had diabetes,  47% had cardiovascular disease and 54% used a RAAS inhibitor. Their mean age was 76 years, mean eGFR 17 mL/min/1.73 m², and mean subjective global assessment 6.0. Over the 8 years, 414 (24%) died before starting KRT and 595 (35%) started KRT. 

When analyses were adjusted for potential confounders, a U-shaped relationship between serum potassium and the combined outcome was found across the seven categories: 1.6; 1.4; 1.1; 1 (reference); 1.1; 1.8 and 2.2. The lowest risk was at a serum potassium level of 4.9 mmol/L.

The prevention of high potassium levels is often the aim of in people with CKD. However, the increased risks observed in this study at both low and high levels of potassium, and the relatively high optimum level, stress the potential importance of also preventing low levels of serum potassium in this older population with CKD.

The full study can be read here.