Sodium alignment in clinical practice--implementation and implications

Numerous reports in the general and the dialysis population have shown associations of sodium (Na(+)) intake, blood pressure, and survival. In addition to dietary Na(+) intake, positive Na(+) balance during dialysis needs to be considered as a source of Na(+). Dialysate Na(+) (DNa(+)) concentrations above the serum Na(+) concentration (SNa(+)) result in diffusive Na(+) flux from the dialysate into the patient, which has recently been reported to be associated with increased interdialytic weight gain and mortality. Individualization of the Na(+) prescription and Na(+) alignment (DNa(+) equal to SNa(+)) prevents positive Na(+) balance and improves patient outcomes. Alignment requires the knowledge of patients' SNa(+), which can be estimated from previous SNa(+) in the monthly routine laboratory measurements. Na(+) alignment was recently implemented in a dialysis clinic of Renal Research Institute. Preliminary results of this initiative have shown a trend of predialysis weight and blood pressure reduction. Expansion of this initiative to all clinics of RRI is currently underway and as of April 2011, four additional clinics have been included. Additional research on adequate Na(+) alignment is needed to account for Gibbs-Donnan effects, differences in charge across the dialyzer membrane, and variability in measurement methods. Regular calibration of DNa(+) delivery by dialysis machines is necessary to ensure that the dialysis prescription is followed. How to provide dialysis to severely hyponatremic patients remains an open question. Finally, long-term studies of the effects of Na(+) restriction on hospitalization and mortality are required to demonstrate the benefits of aligning DNa(+) with SNa(+).