Too high, too low potassium levels bad for older patients with advanced CKD

High and low levels of serum potassium appear to contribute to an increase in the risk of death or kidney failure requiring replacement therapy (KRT) among older patients with chronic kidney disease (CKD) stage 4‒5, according to a study.

The prospective observational cohort study included 1,714 patients aged ≥65 years from the European QUALity (EQUAL) study. These patients were followed for 8 years from their first estimated glomerular filtration rate (eGFR) <20ml/min/1.73 m² measurement. Serum potassium was measured every 3–6 months and categorized as: ≤3.5, >3.5‒≤4.0, >4.0‒≤4.5, >4.5‒≤5.0 (reference), >5.0‒≤5.5, >5.5‒≤6.0 and >6.0 mmol/L.

The mean age of the cohort was 76 years, and 66 percent were men. Many patients had diabetes (42 percent), had cardiovascular disease (47 percent), and used renin–angiotensin–aldosterone system inhibitors (54 percent). The mean eGFR at baseline was 17 ml/min/1.73 m², and the mean subjective global assessment was 6.0.

Over the follow-up, a total of 414 (24 percent) patients died before starting KRT while 595 (35 percent) started KRT. There was a U-shaped relationship between serum potassium and the combined outcome of KRT initiation or death before KRT. The corresponding adjusted hazard ratios for the combined outcome according to the potassium categories were as follows: 1.6 with ≤3.5 mmol/L, 1.4 with >3.5‒≤4.0 mmol/L, 1.1 with >4.0‒≤4.5 mmol/L, 1.1 with >5.0‒≤5.5 mmol/L, 1.8 with >5.5‒≤6.0 mmol/L, and 2.2 with >6.0 mmol/L. The risk was lowest at a potassium level of about 4.9 mmol/L.

The findings highlight the potential importance of preventing both hypo- and hyperkalemia in patients with CKD stage 4‒5.