Original Investigation
Dialysis
Lowering Postdialysis Plasma Sodium (Conductivity) to Increase Sodium Removal in Volume-Expanded Hemodialysis Patients: A Pilot Study Using a Biofeedback Software System

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Background

Extracellular fluid expansion is common in hemodialysis patients. Aggressive fluid removal may lead to intradialytic complications. High dialysate sodium concentrations may lessen complications, but may increase extracellular volume. We hypothesized that decreasing plasma sodium concentration during dialysis will increase sodium removal and decrease extracellular volume.

Study Design

Pilot clinical trial.

Setting & Participants

16 patients with end-stage kidney disease treated using thrice-weekly hemodialysis at a university teaching hospital hemodialysis unit.

Intervention

Stepwise decrease in postdialysis plasma sodium level (calculated as end-of-session plasma conductivity) over 4 phases effected by dialysate conductivity measurement cells and a biofeedback software system (Diacontrol; Hospal, www.hospal.it) that allowed alteration of dialysate inlet conductivity and calculation of plasma conductivity.

Outcomes

Decrease in postdialysis plasma sodium (conductivity) levels, sodium removal, redistribution of body water, and effect of these on interdialytic weight gain and blood pressure.

Measurements

Plasma sodium and conductivity values (the latter measured in millisiemens per centimeter); ionic mass balance (sodium removal); bioelectrical impedance analysis measurements of body-water compartments and phase angle; interdialytic weight gain; and blood pressure.

Results

Plasma sodium concentrations at the end of dialysis were decreased from 137.8 (phase 1) to 135.6 mmol/L (phase 4) and end-of-session plasma conductivity values were decreased from 14.0 (phase 1) to 13.5 mS/cm (phase 4; all mean values). Ionic mass balance increased from 383 to 480 mmol. Extracellular water was significantly decreased, phase angle was increased, and blood pressure and interdialytic weight gain were decreased. Plasma sodium levels correlated significantly with plasma conductivity; thus, changes in postdialysis plasma sodium levels can be inferred from changes in end-of-session plasma conductivity values.

Limitations

Small number of patients. No information for dietary sodium intake.

Conclusion

To decrease extracellular volume, it may be necessary to add diffusive to convective sodium losses.

Section snippets

Setting and Patients

Sixteen patients with end-stage renal failure receiving maintenance out-patient hemodialysis treatments 3 times weekly at the Adam Linton Dialysis Unit, Victoria Hospital, London Health Sciences Centre, London, Canada, were studied. All had a well-functioning dialysis blood access (arteriovenous fistula, graft, or cuffed tunneled central catheter). All were chosen because of known stability during dialysis treatments and the ability to give informed consent. No patient was enrolled in another

Results

All 15 patients tolerated the individualized gradual decrease in postdialysis target plasma conductivity with very minimal symptoms during the 7-week period. There were 4 episodes of intradialytic hypotension (decrease in systolic blood pressure >20 mm Hg) during the entire study period, none of which required intervention. The primary end points of interest were the decrease in plasma conductivity, changes in total ionic mass balance, and BIA measurements (quantifying body-water distribution

Discussion

Persistent volume overload in patients with end-stage renal failure is common and is one of the primary determinants of cardiovascular morbidity and mortality.1, 2, 3, 12 This fluid-overloaded state is caused by salt and water retention. Unfortunately, salt and water removal by hemodialysis is limited by the rate of intravascular refilling; thus, cramping and symptomatic hypotension are common.4, 5, 6 Shortening hemodialysis treatment times and the common clinical practice of universal rather

Acknowledgements

Support: Grant support was provided from The University of Western Ontario, Division of Nephrology Academic Fund.

Financial Disclosure: The authors declare that they have no relevant financial interests.

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Originally published online as doi:10.1053/j.ajkd.2009.12.037 on March 22, 2010.

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Copyright © 2010 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.