The pivotal role of sodium balance in control of blood pressure in dialysis patients

In hemodialysis patients, as in patients with normal kidney function, sodium balance is the major determinant of changes in extracellular volume, and extracellular volume is an important determinant of blood pressure. The osmotic thresholds for thirst and ADH release are normal in kidney failure; pre-dialysis serum sodium concentration shows a high index of individuality in oliguric hemodialysis patients. Non-osmotic storage of sodium in vascular walls may also amplify the volume-sensitivity of blood pressure. The variable relationship between volume removal and change in blood pressure described in clinical studies reflects a state of permanent volume expansion in those whose blood pressure does not fall, or rises, during dialysis, whereas those whose blood pressure falls during dialysis are those who approach normovolemia. Rigorous control of extracellular volume often results in perfect blood pressure control, but may be difficult to achieve safely other than with long, slow dialysis combined with dietary salt restriction.