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Abstract: FR-PO742

Accuracy of Dialysate Sodium from Dialysate Conductivity Compared to Measured Sodium: A Quality Assurance Study

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Brown, Pierre-Antoine, University of Ottawa, Ottawa, Ontario, Canada
  • Sheikh, Rayees Yousuf, The Ottawa Hospital, Ottawa, Ontario, Canada
  • Clark, Edward George, University of Ottawa, Ottawa, Ontario, Canada
  • Akbari, Ayub, University of Ottawa, Ottawa, Ontario, Canada
  • Hiremath, Swapnil, University of Ottawa, Ottawa, Ontario, Canada

Dialysate sodium is traditionally set at a constant with the intention of providing isonatric dialysis. A dialysate sodium higher than plasma levels can result in transfer of sodium to the patient, while a lower sodium can lead to cramps and hypotension. Modulations of dialysate sodium are done by changing dialysate conductivity, since sodium is the primary driver of conductivity. Recent studies have suggested that the agreement between dialysate conductivity and measured dialysate sodium is imperfect. This quality assurance study was designed to examine the bias between machine reported conductivity and measured dialysate sodium and determine the factors associated with the bias, if present.


We conducted patient-free dialysis sessions using 3 different dialysis machines (Gambro Artis, Bellco Formula and Fresenius 4008) with varying sodium and potassium baths. Machine reported conductivity was recorded at time 0, 1hour, 2 hour, and 4 hours. Concurrently, dialysate samples were sent for measurement of sodium (indirect ion selective [ISE] method) and other electrolytes. A total of 46 sessions with different sets of dialysate sodium (135 mEq/L or 140 mEq/L) and K baths (2 mEq/L or 3mEq/L) were analyzed.


At all 4 time points, the measured dialysate sodium was significantly higher than the set dialysate sodium. At T0, the difference was 6.11 + 1.62 mEq/L (mean +/- SD) with similar results noted for all time points. The difference between measured and set dialysate sodium was higher for 3K (6.48 + 1.85 mEq/L) bath than 2K bath (5.58 + 1.07 mEq/L) (p=0.003), but not different whether set sodium was 135 or 140 (p = 0.80). There also was a difference between the 3 models of HD machines tested; model one: 6.23 + 1.36 mEq/L; two: 4.80 + 1.93 mEq/L; three: 7.10 + 1.10mEq/L; p=0.0035.


Our analysis shows that, for 3 common dialysis machine models, there is a significant difference between the ordered dialysate sodium (I.e. conductivity) and the measured dialysate sodium. The bias persists throughout session time, and a range of common sodium and potassium baths. It is large enough to have clinical implications.