Optimal composition of the dialysate, with emphasis on its influence on blood pressure

Introduction. From the beginning of the dialysis era, the most appropriate composition of the dialysate has been one of the central topics in the delivery of dialysis treatment.

A discussion is employed to achieve a consensus on key points relating to the composition of the dialysate, focusing on the relationships with blood pressure behaviour.

Sodium balance is the cornerstone of intra-dialysis cardiovascular stability and good inter-dialysis blood pressure control. Hypernatric dialysis carries the risk of positive sodium balance, with the consequent possibility of the worsening sense of thirst and hypertension. Conversely, hyponatric dialysis may lead to negative sodium balance, with the possibility of intra-dialysis cardiovascular instability and 'disequilibrium' symptoms including fatigue, muscle cramps and headache. The goal is to remove with dialysis the exact amount of sodium that has accumulated in the inter-dialysis interval. The conductivity kinetic model is applicable on-line at each dialysis session and has been proved to be able to improve intra-dialytic cardiovascular stability in hypotension-prone patients. Therefore, it should be regarded as a promising tool to be implemented in everyday clinical practice. Serum potassium concentration and variations during dialysis treatment certainly play a role in the genesis of cardiac arrhythmia. Potassium profiling, with a constant gradient between plasma and dialysate, should be implemented in clinical practice to minimize the arrhythmogenic potential of dialysis. Calcium plays a role both in myocardial contractility and in peripheral vascular resistance. Therefore, an increase in dialysate calcium concentration may be useful in cardiac compromised hypotension-prone patients. Acid-buffering by means of base supplementation is one of the major roles of dialysis. Bicarbonate concentration in the dialysate should be personalized in order to reach a midweek pre-dialysis serum bicarbonate concentration of 22 mmol/l. The role of convective dialysis techniques in cardiovascular stability is still under debate. It has been demonstrated that dialysate temperature and sodium balance play a role and this should be taken into account. Whether removal of vasoactive, middle-sized compounds by convection plays an independent role in improving cardiovascular stability is still uncertain.

The prescription of dialysis fluid is moving from a pre-fixed, standard dialysate solution to individualization of electrolyte and buffer composition, not only during the dialysis session, but also within the same session (profiling) in order to provide patients with an optimal blood purification coupled with a high degree of tolerability.