Dry weight and sodium balance

To achieve good blood pressure control and minimal intradialytic patient discomfort, it is very important to define the correct dry weight and individualize the "adequate" dialysate sodium concentration. Given the highly variable amounts of sodium introduced during interdialytic periods, the use of the sodium and conductivity kinetic models guarantees adequate sodium removal in each patient with each treatment. According to our data, the imprecision of the sodium kinetic model was less than 0.84 mEq/L; that of the conductivity kinetic model, which has the advantage not requiring blood or dialysate samples, was less than 0.14 mS/cm. In paired filtration dialysis (PFD), the corresponding figures were less than 1.1 mEq/L and less than 0.1 mS/cm. A multicenter prospective, controlled and randomized trial has demonstrated that the application of the conductivity kinetic model in PFD makes it possible to improve cardiovascular stability in patients prone to dialysis hypotension. The sodium kinetic model is difficult to apply in routine clinical practice because of the need for blood and dialysate samples, but this may be overcome by the conductivity kinetic model, which is a very promising tool for achieving a zero intradialytic sodium balance and improving cardiovascular stability.