[Water-sodium homeostasis in hemodialysis - the eternal problem in nephrology practice].

The kidney is an organ that maintains the body's sodium and water balance and plays a significant role in blood pressure regulation. Chronic kidney disease (CKD) and a progressive loss of its function, among others, leads to sodium and water retention and, as a consequence, to arterial hypertension. The supply of salt and fluids delivered with the diet significantly affects the cardiovascular system's functioning particularly in hemodialysis patients. The critical element in clinical care is maintaining appropriate water and electrolyte homeostasis. Overhydration is manifested as oedema and blood preassure increase, but a more accurate assessment of subtle variations is possible by measuring bioelectric impedance (BIA), which determines the extracellular water index (ECW). Actions to maintain euvolemia include limiting sodium and fluid intake, regular assessment of "dry" body weight, proper selection of ultrafiltration (UF), correction of sodium concentration, and dialysate temperature.