Abstract
BackgroundA 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.MethodsIn 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.ResultsComparing 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).ConclusionsA 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 NumberNCT01224314
Highlights
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
Predialysis serum potassium was in turn comparable, while, as expected, post-dialysis serum potassium was influenced mainly by the potassium concentration in the dialysate during the last dialysis tertile, producing significant differences (p < 0.01) between the sequences that ended with the usual dialysate potassium concentration, supplemented by 1 or reduced by 1 mmol/l (Table 3)
The study showed that a low potassium concentration in the dialysate, inducing a rapid decrease in serum potassium, causes a decrease in systolic and mean blood pressure correlated with a decrease in peripheral resistance
Summary
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. 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. The importance of the body content and serum concentration of potassium to control blood pressure remains controversial. An acute decrease in serum potassium concentration produces vasocostriction mediated by the vascular endothelium and an increase in myocardial contractility; the opposite effect is observed if it increases [11,13]
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