Potassium handling in chronic hemodialysis patients in response to higher dialysate potassium

Rationale:
In hemodialysis patients, hyperkalemia is often attributed to dietary potassium intake. Some differentiations, however, are to be made. That is, hyperkalemia may also be caused by changes in the internal potassium balance. A cohort study showed that urea levels, metabolic acidosis, and hyperglycemia but not anuria or hyperkalemic drugs were associated with pre-dialysis serum potassium concentrations. Moreover, as in non-dialysis CKD, total body potassium (TBK) has been shown to be decreased in dialysis patients. Importantly, a lower TBK in hemodialysis patients provides prognostic information as median survival was recorded to be 55 months in TBK-depleted subjects vs. 100 months in subjects with normal TBK. Lowering of serum potassium by the dialysate was associated with higher blood pressure levels one hour post-dialysis. Moreover, serial measurements of total body minerals showed that a TBK increment was associated with lower total body sodium (TBNa), although other studies could not reproduce this observation.[1],[2] In summary, a higher potassium dialysate concentration may restore TBK. Whether this would also lead to improved blood pressure regulation, increased sodium removal, and better volume control is unknown.

Objective: To analyze how potassium handling, volume and sodium status change in stable anuric chronic hemodialysis patients (CKD-5D) in response to higher dialysate potassium.

Study design: Single-blind, interventional cross-over study.

Study population: Stable anuric hemodialysis patients that undergo treatment 3 x 4 hrs/week.

Intervention: Hemodialysis patients will be treated using widely used dialysate solutions as part of standard care containing potassium either 2 mmol/L or 4 mmol/L in random order.

Main study parameters/endpoints: The primary outcome will be RBC potassium. Secondary endpoints will include serum potassium, potassium removal, serum sodium, sodium removal, total ultrafiltration volume, total body water, and systolic blood pressure as well as changes in serum bicarbonate, insulin, and plasma aldosterone.

1. Serum potassium in hemodialysis patients (CKD stage 5D) is mainly influenced by alterations in the internal potassium balance.
2. Higher dialysate potassium in CKD-5D increases the potassium erythrocyte concentration as proxy for TBK.
3. The increase in TBK by higher dialysate potassium reduces total body sodium stores in CKD-5D.

After 4 weeks of dialysis with dialysate solutions containing potassium either 2 mmol/L or 4 mmol/L there will be a study visit.

Hemodialysis patients will be treated using widely used dialysate solutions as part of standard care containing potassium either 2 mmol/L or 4 mmol/L in random order.