Haemodynamic consequences of changing potassium concentrations in haemodialysis fluids

Abstract

Background: A rapid decrease of serum potassium concentrations during haemodialysis produces a significant increase in blood pressure parameters at the end of the session, even if effects on intra-dialysis pressure are not seen. Paradoxically, in animal models potassium is a vasodilator and decreases myocardial contractility. The purpose of this trial is to study the precise haemodynamic consequences induced by acute changes in potassium concentration during haemodialysis.

Methods: In 24 patients, 288 dialysis sessions, using a randomised single blind crossover design, we compared six dialysate sequences with different potassium profiles. The dialysis sessions were divided into 3 tertiles, casually modulating potassium concentration in the dialysate between the value normally used K and the two cut-off points K+1 and K-1 mmol/l. Haemodynamics were evaluated in a non-invasive manner using a finger beat-to-beat monitor.

Results: Comparing K-1 and K+1, differences were found within the tertiles regarding systolic (+5.3, +6.6, +2.3 mmHg, p < 0.05, < 0.05, ns) and mean blood pressure (+4.3, +6.4, -0.5 mmHg, p < 0.01, < 0.01, ns), as well as peripheral resistance (+212, +253, -4 dyne.sec.cm-5, p < 0.05, < 0.05, ns). The stroke volume showed a non-statistically-significant inverse trend (-3.1, -5.2, -0.2 ml). 18 hypotension episodes were recorded during the course of the study. 72% with K-1, 11% with K and 17% with K+1 (p < 0.01 for comparison K-1 vs. K and K-1 vs. K+1).

Conclusions: A rapid decrease in the concentration of serum potassium during the initial stage of the dialysis-obtained by reducing the concentration of potassium in the dialysate-translated into a decrease of systolic and mean blood pressure mediated by a decrease in peripheral resistance. The risk of intra-dialysis hypotension inversely correlates to the potassium concentration in the dialysate.

Trial registration number: NCT01224314.

Figures

Figure 1

Systolic blood pressure. Systolic blood pressure as a function of the dialysis tertiles in the 6 dialysate sequences (1 to 6).

Figure 2

Mean blood pressure. Mean blood pressure as a function of the dialysis tertiles in the 6 dialysate sequences (1 to 6).

Figure 3

Peripheral resistance. Total peripheral resistance as a function of the dialysis tertiles in the 6 dialysate sequences (1 to 6).

Figure 4

Stroke volume. Stroke volume as a function of the dialysis tertiles in the 6 dialysate sequences (1 to 6).

Figure 5

Systolic blood pressure. Systolic blood pressure as a function of dialysis tertiles comparing treatments with the two potassium (K) concentration cut-off points in the dialysate (high = K+1 and low = K-1). P for the 1st, 2nd and 3rd tertiles: < 0.05, < 0.05 and ns respectively.

Figure 6

Mean blood pressure. Mean blood pressure as a function of dialysis tertiles comparing treatments with the two potassium (K) concentration cut-off points in the dialysate (high = K+1 and low = K-1). P for the 1st, 2nd and 3rd tertiles: < 0.01, < 0.01 and ns respectively.

Figure 7

Total peripheral resistance. Total peripheral resistance as a function of dialysis tertiles comparing treatments with the two potassium (K) concentration cut-off points in the dialysate (high = K+1 and low = K-1). P for the 1st, 2nd and 3rd tertiles: < 0.05, < 0.05 and ns respectively.

Figure 8

Stroke volume. Stroke volume as a function of dialysis tertiles comparing treatments with the two potassium (K) concentration cut-off points in the dialysate (high = K+1 and low = K-1). P for the 1st, 2nd and 3rd tertiles: ns.

Figure 9

Incidence of hypotension episodes. Incidence of hypotension episodes as a function of the dialysate potassium (K) concentration. P for the differences between both K-1 and K and K-1 and K+1 < 0.01; n = 18.