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Medical Associates  ·  Department of Nephrology ← Maintenance Hemodialysis module  ·  urinenephrology.org
Clinical Mastery Series  ·  Maintenance Hemodialysis

Dialysate sodium: BP, thirst, IDH, and the RESOLVE question

Sodium balance, the set point, the randomized and observational evidence, and how to prescribe while RESOLVE is pending
Andrew Bland, MD, FACP, FAAP UICOMP · UDPA · Butler COM Reviewed September 2026 13 min read

Bottom line

Part of the Maintenance Hemodialysis mastery module. Sodium in mEq/L equals mmol/L. IDWG = interdialytic weight gain; IDH = intradialytic hypotension.

  • Lower dialysate sodium buys a little and costs a little. Below 138 mEq/L lowers IDWG (−0.36 kg, high certainty) and pre-dialysis mean arterial pressure (−3.4 mmHg, moderate certainty), and increases intradialytic hypotension (RR 1.58) and cramps (RR 1.84) per session (moderate certainty) 1.
  • Large observational cohorts point the other way on survival. Dialysate sodium of 138 mEq/L or less was associated with higher mortality (HR 1.57, 1.25–1.98) in 68,196 incident patients 2, a signal open to confounding by indication 3.
  • RESOLVE (137 versus 140 mmol/L, cluster-randomized) has not reported as of 26 September 2026 4. Do not cite RESOLVE effect sizes until a results paper appears.
  • Defensible now: a default of 137–140 mEq/L, no hypernatremic dialysate 5, movement toward the patient’s own pre-dialysis sodium (not below 135) when IDWG or hypertension is the problem, and no routine sodium profiling.
  • Raising sodium has a blood-pressure price. Moving from 135 to 140 mEq/L cut the odds of intradialytic hypotension by about a third (OR 0.66) but raised pre-dialysis BP by 7.0/3.9 mmHg 6. Fix time, ultrafiltration rate, and temperature first.
  • Severe chronic hyponatremia needs a different prescription: the lowest available dialysate sodium, blood flow of 50–100 mL/min, short daily sessions, and hourly sodium checks, keeping the rise within 4–8 mEq/L per 24 hours 7,8.

1. Physiology: gradient, set point, and balance

Practice clusters tightly: in DOPPS, 90% of dialysate sodium prescriptions fell between 138 and 142 mEq/L, and in the NephroCare cohort 63% were 138 2,9. Sodium crosses the dialyzer by two routes. Convection carries sodium out with ultrafiltrate at roughly plasma-water concentration. Diffusion moves sodium down the gradient between dialysate and plasma water. Because of the Donnan effect, the “isonatric” dialysate (zero net diffusive flux without ultrafiltration) sits slightly below plasma sodium activity 10; in practice, a dialysate sodium up to about 3 mEq/L below measured serum sodium produces approximately zero diffusive transfer 7. A dialysate above that point loads sodium during the session; below it, the session removes sodium by diffusion as well as convection.

Two observations anchor the “set point” idea. A patient’s pre-dialysis serum sodium is stable over time and is not moved by the dialysate sodium prescription 11,12. And the gradient between dialysate sodium and that stable pre-dialysis value tracks IDWG and blood pressure: sodium loaded during treatment raises post-dialysis tonicity, the patient drinks back to the set point, and the water arrives as weight gain at the next session 13,14. Tissue stores in skin and muscle add a slowly exchanging compartment that one session does not clear 15.

The 2019 KDIGO Controversies Conference states the goal plainly: sodium balance should be negative during a hemodialysis treatment, and hypernatremic dialysis should be avoided 5.

Higher dialysate sodiumLower dialysate sodium
Preserves plasma volume and refilling; fewer hypotensive episodes and crampsMore hypotension and cramps
Loads sodium; raises thirst, IDWG, and blood pressure over the following daysLess thirst, lower IDWG, lower blood pressure
The next session needs more ultrafiltrationThe next session needs less ultrafiltration

2. Observational outcome data

StudyPopulationFindingAppraisal
Hecking 2012, CJASN (DOPPS) 1629,593 patientsIDWG +0.17% of body weight per 2 mEq/L higher dialysate sodium. Mortality HR 0.98 (0.95–1.02) per 2 mEq/L overall; HR 0.88 (0.83–0.94) in facilities where 90%–100% of patients shared one sodiumHigher sodium raised weight gain yet was associated with lower mortality in the least-confounded analysis
Hecking 2012, AJKD (DOPPS) 1111,555 patients, 12 countriesMortality HR 0.95 (0.93–0.97) per 1 mEq/L higher serum sodium. Dialysate sodium did not predict serum sodium. With serum sodium below 137, dialysate above 140 was associated with lower mortalityHypothesis-generating
Mc Causland 2012 122,272 patientsHigher dialysate sodium associated with mortality only at higher serum sodiumEffect modification by serum sodium
Pinter 2024, JASN (NephroCare, 25 countries) 268,196 incident patients; 63.2% on 138 mEq/LDialysate sodium 138 or lower vs above 138: mortality HR 1.57 (1.25–1.98), adjusted for plasma sodium and bioimpedance fluid statusLargest cohort; provider data and provider-affiliated authors; low sodium is often prescribed to sicker, overloaded, hypertensive patients
Christa 2025 (same cohort) 1768,196Cumulative exposure to 138 or lower: HR for heart-failure death peaking at 6.0 (1.9–18.3), sudden cardiac death 2.7 (1.3–5.6), all-cause 2.0 (1.3–3.1)Same data source and limits

The RESOLVE investigators answered the 2024 cohort in the same journal issue with a perspective asking whether observational reports on dialysate sodium and mortality are enough to change practice 3. That is the right question. The observational signal is largely consistent in direction across DOPPS and NephroCare (one US cohort found the association depended on serum sodium 12), and it runs against the intuition that lower sodium must be better.

3. Randomized trials

SoLID (RCT, 2020)

Ninety-nine home and self-care satellite patients with pre-dialysis serum sodium of 135 mEq/L or higher were randomized to dialysate sodium 135 versus 140 mEq/L for 12 months 18. The primary outcome, left ventricular mass index by cardiac MRI, did not change, despite lower IDWG, extracellular fluid volume, and BNP in the low-sodium arm. Intradialytic hypotension rose (OR 7.5, 1.1–49.8, at 6 months; 3.6, 0.5–28.8, at 12 months), and five participants in the low-sodium arm could not complete the trial because of hypotension. Thirst, xerostomia, dietary sodium, and quality of life did not change 18.

Appraisal: a surrogate primary endpoint in a selected, healthier self-care population, with wide confidence intervals for hypotension. It does not support the claim that lowering dialysate sodium regresses LV mass within a year, although a two-trial pooled estimate in the 2024 Cochrane review suggests a modest reduction 1.

Miskulin (RCT, 2024)

Forty-two participants were randomized 2:1 to 135 versus 138 mEq/L for 6 months, followed by a 12-week extension in which the low-arm participants were raised to 140 mEq/L 6.

  • Randomized phase (135 vs 138): intradialytic hypotension, the primary outcome, did not differ (ratio of slopes 0.96, 0.26–3.61). Symptom scores were worse at 135 (difference 6.0, 2.1–9.8). IDWG fell by 0.6 kg relative to 138. Pre-dialysis BP did not change.
  • Extension (135 to 140, within-patient): IDWG +0.2 kg (0.1–0.3), pre-dialysis BP +7.0/+3.9 mmHg, and intradialytic hypotension OR 0.66 (0.45–0.97).

Appraisal: small; the extension is a non-randomized before-after comparison in the low arm only; investigators report salary support from a dialysis provider 6. The asymmetry is the useful part. Going down from 138 bought a little weight and nothing on BP at the cost of symptoms; going up to 140 bought fewer hypotensive episodes at a measurable BP price.

Cochrane review (2024)

Seventeen RCTs, 509 patients, median follow-up 4 weeks, comparing low (below 138 mEq/L) with neutral or high (138 or above) dialysate sodium 1:

OutcomeEffect of low dialysate sodiumCertainty
IDWGMD −0.36 kg (−0.50 to −0.22)High
Antihypertensive useSMD −0.37 (−0.64 to −0.10)High
LV mass index (2 studies)MD −7.65 g/m² (−14.48 to −0.83)Moderate
Pre-dialysis MAPMD −3.39 mmHg (−5.17 to −1.61)Moderate
Pre-dialysis serum sodiumMD −1.26 mEq/L (−1.81 to −0.72)Moderate
Intradialytic hypotensionRR 1.58 (1.25–2.01) per sessionModerate
CrampsRR 1.84 (1.29–2.64) per sessionModerate
Death, cardiovascular events, hospitalizationNot studied—

ARR and NNT cannot be derived, because the review reports per-session risk ratios without a pooled baseline event rate.

Intradialytic hypertension and smaller trials

In a randomized crossover of 29 patients with intradialytic hypertension, 137 versus 140 mEq/L for four sessions each lowered 48-hour ambulatory BP to 137.6/81.4 from 142.9/84.0 mmHg, with lower IDWG and fewer lung-ultrasound B-lines 19. This is the patient in whom lowering sodium has the clearest short-term payoff (see Intradialytic hypertension and the stability trade-off). A 45-patient study moving sodium in 2 mmol/L steps between 138 and 142 found limited support for meaningful peridialytic BP change 20. A 28-patient crossover of 132 versus 138 mEq/L found no significant difference in muscle or skin sodium by 23Na-MRI over 4 weeks 21.

4. RESOLVE: status as of September 2026

RESOLVE (Randomised Evaluation of Sodium dialysate Levels on Vascular Events; NCT02823821) cluster-randomizes dialysis units to a default dialysate sodium of 137 or 140 mmol/L, with a primary outcome of hospitalized myocardial infarction, hospitalized stroke, or all-cause death over an average of 5 years 4. The trial registry lists it as recruiting (last update April 2025), with estimated enrollment of 50,000, estimated primary completion in December 2026, and no posted results 4. A PubMed search on 26 September 2026 found the team’s 2024 perspective 3 but no results publication.

Do not cite RESOLVE results

As of this review, RESOLVE has neither been published nor posted results. Any source that quotes RESOLVE effect sizes should be treated as unverified until a results paper appears.

5. Individualized sodium and sodium profiling

Individualization

In a single-blind crossover of 27 non-diabetic, non-hypotension-prone patients, setting dialysate sodium from each patient’s own pre-dialysis plasma sodium instead of a standard 138 mEq/L lowered IDWG from 2.91 to 2.29 kg, reduced thirst, and reduced intradialytic hypotension; pre-dialysis BP fell only in patients with uncontrolled BP 22. The set-point and gradient literature supports matching dialysate sodium to the patient’s stable pre-dialysis value 13,14. Two cautions apply. Individualization is only as good as the delivered sodium, which can differ from the prescribed number 5,7,23. And hard-outcome evidence for individualization does not exist.

Profiling

In a 33-patient randomized crossover, combined sodium and ultrafiltration profiling reduced symptomatic sessions from 30.6% to 20.4% (OR 0.61, 0.39–0.96), with pre-dialysis weight 0.3 kg higher on profiled treatments 24. That is an RRR of 33%, an ARR of 10.2%, and an NNT of 10 sessions to prevent one symptomatic session 24.

The patient experiences the time-averaged sodium. A high-to-low profile whose average sits above the patient’s set point is a sodium load delivered early, and it shows up as weight gain. Routine sodium profiling is not recommended; a standing profile is defensible only when its time-averaged sodium is stated and sits at or below the fixed-sodium target 24. Observational data on profiling and mortality are discussed in Intradialytic hypotension and dialysate cooling.

6. Practical prescribing

SituationSuggested approachBasis
Default for a unit or a new patient137–140 mEq/LObservational harm signal at 138 or below 2,17; Cochrane harms below 138 1; RESOLVE pending 4
High IDWG, interdialytic hypertension, preserved hemodynamicsMove toward the patient’s averaged pre-dialysis sodium, not below 135; watch cramps and hypotension1,13,14,22
Intradialytic hypertension137 mEq/L is reasonable19
Hypotension-proneFix time, UF rate, and temperature first; 140 mEq/L if needed; avoid above 140 as a standing order5,6
Standing profilesOnly with a stated time-averaged sodium at or below the fixed-sodium target24
NeverHypernatremic dialysate as routine5

The non-sodium levers for intradialytic hypotension—treatment time, ultrafiltration rate, and dialysate temperature—should come first because they do not cost interdialytic blood pressure. They are covered in Ultrafiltration rate and treatment time and Intradialytic hypotension and dialysate cooling.

Pre-dialysis serum sodium, averaged over recent months
Below 130 mEq/L or an acute drop? Hyponatremia pathway (section 7).
↓ if no: what is the main problem?
High IDWG or interdialytic hypertension
Match dialysate to the patient’s sodium, not below 135
Intradialytic hypertension
Consider 137
Intradialytic hypotension
Fix time, UF rate, and temperature first; then 140 if needed
Neither
Default 137 to 140
Monitor cramps, intradialytic hypotension, IDWG, and home blood pressure
Figure 1. Choosing dialysate sodium. Synthesized from 1,5,6,13,14,19,22; expert synthesis, not a tested algorithm.

7. The hyponatremic patient and osmotic demyelination

Chronic mild hyponatremia is common and prognostic. In 1,549 oligoanuric HEMO participants, each 4 mEq/L higher pre-dialysis sodium was associated with lower mortality (adjusted HR 0.89, 0.82–0.96) 25, and DOPPS found the same gradient 11. Because vasopressin cannot act on a kidney that makes no urine, this is one of the cleaner human signals that hyponatremia itself may matter 25.

Severe chronic hyponatremia (below 120 mEq/L, developing over more than 48 hours) needs a different prescription. Adapted brain cells have shed organic osmolytes and are vulnerable to osmotic demyelination if sodium rises fast 7. Uremia appears partly protective—none of 52 azotemic patients whose sodium rose by 12 mEq/L or more with standard hemodialysis developed osmotic demyelination 26—but post-hemodialysis cases are reported, so the non-dialysis correction limit of 4–8 mEq/L per 24 hours applies 7.

How to do it with intermittent hemodialysis 7,8:

  1. Lowest available dialysate sodium, usually 130 mEq/L.
  2. Low blood flow, 50–100 mL/min, which throttles sodium delivery.
  3. Short sessions of 2–3 hours, repeated daily.
  4. Hourly serum sodium during treatment, with 5% dextrose in water if the rise outruns the target.
  5. CRRT with custom replacement-fluid sodium, when available, is the more controllable option 7.

A published case shows the method working: serum sodium 112 mEq/L, dialysate 130 mEq/L, blood flow 50 mL/min, with the rise limited to about 2 mEq/L per hour 8. Severe acute hyponatremia (onset under 48 hours, as in water intoxication) is the opposite problem, cerebral edema, and conventional dialysis with standard sodium is appropriate 7. For correction principles outside dialysis, see Hyponatremia correction.

First treatments and disequilibrium. For the uremic patient starting dialysis, the concern reverses: rapid urea removal lowers plasma osmolality and can drive water into the brain. Higher dialysate sodium relative to plasma (144–154 mmol/L studied) helps hold plasma osmolality during high-efficiency first treatments, alongside reduced clearance, and a lower bicarbonate dialysate with more gradual acidosis correction has been suggested 27.

Clinical Pearl

The patient with a sodium of 118 and a BUN of 140 needs two opposing osmotic brakes at once: a low dialysate sodium to keep sodium from rising too fast, and low blood flow with a short session to keep urea from falling too fast. Low blood flow happens to serve both.

Evidence gaps

  • No completed hard-outcome RCT of dialysate sodium. RESOLVE is the trial that could change practice, and it has not reported 4.
  • Whether the observational mortality signal at 138 or below survives randomization is unknown 2,3.
  • Whether individualized sodium beats a well-chosen standard on hard outcomes has not been tested 22.
  • Delivered versus prescribed sodium: routine auditing of delivered dialysate sodium is rare, and prescribed values can differ from delivered ones 5,23.
  • Randomized data are short and small: the Cochrane pooled trials had a median follow-up of 4 weeks and did not study death, cardiovascular events, or hospitalization 1.

At the chair

For dialysis nurses and technicians

Enter dialysate sodium and any profile exactly as ordered. Raising dialysate sodium to treat cramps or low blood pressure is a prescription change: each step up is repaid as thirst, weight gain, and higher blood pressure over the next two days 6. Report a pre-dialysis serum sodium that is markedly low or has fallen sharply from the patient’s usual value before starting, because severe chronic hyponatremia needs a special prescription.

Nursing card N2: Dialysate prescription check — do this, call when, don’t, and why

The physician’s written order and the unit protocol always govern.

Also in this module

References

References are carried from a reference-checked evidence review (September 2026) and renumbered for this page. Each was checked against its PubMed record, full text, or the issuing agency’s document.

  1. Marshall MR, Wang MY, Vandal AC, Dunlop JL. Low dialysate sodium levels for chronic haemodialysis. Cochrane Database Syst Rev. 2024;11:CD011204. PMID: 39498822
  2. Pinter J, Smyth B, Stuard S, et al. Effect of dialysate and plasma sodium on mortality in a global historical hemodialysis cohort. J Am Soc Nephrol. 2024;35(2):167-176. PMID: 37967469
  3. Smyth B, Krishnasamy R, Jardine M; RESOLVE Study Global Team. Are observational reports on the association of dialysate sodium with mortality enough to change practice? Perspective from the RESOLVE Study Team. J Am Soc Nephrol. 2024;35(2):229-231. PMID: 38096088
  4. RESOLVE: Randomised Evaluation of Sodium Dialysate Levels on Vascular Events. ClinicalTrials.gov NCT02823821 (status: recruiting; last update 2025-04-01; primary completion estimated 2026-12; no results posted; accessed 2026-09-26).
  5. Flythe JE, Chang TI, Gallagher MP, et al. Blood pressure and volume management in dialysis: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference. Kidney Int. 2020;97(5):861-876. PMID: 32278617
  6. Miskulin DC, Tighiouart H, Hsu CM, Weiner DE. Dialysate sodium lowering in maintenance hemodialysis: a randomized clinical trial. Clin J Am Soc Nephrol. 2024;19(6):712-722. PMID: 38349776
  7. Pirklbauer M. Hemodialysis treatment in patients with severe electrolyte disorders: management of hyperkalemia and hyponatremia. Hemodial Int. 2020;24(3):282-289. PMID: 32436307
  8. Wendland EM, Kaplan AA. A proposed approach to the dialysis prescription in severely hyponatremic patients with end-stage renal disease. Semin Dial. 2012;25(1):82-85. PMID: 21906168
  9. Ashby D, Borman N, Burton J, et al. Renal Association Clinical Practice Guideline on Haemodialysis. BMC Nephrol. 2019;20(1):379. PMID: 31623578
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  11. Hecking M, Karaboyas A, Saran R, et al. Predialysis serum sodium level, dialysate sodium, and mortality in maintenance hemodialysis patients: the Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis. 2012;59(2):238-248. PMID: 21944663
  12. Mc Causland FR, Brunelli SM, Waikar SS. Dialysate sodium, serum sodium and mortality in maintenance hemodialysis. Nephrol Dial Transplant. 2012;27(4):1613-1618. PMID: 21891777
  13. Keen ML, Gotch FA. The association of the sodium "setpoint" to interdialytic weight gain and blood pressure in hemodialysis patients. Int J Artif Organs. 2007;30(11):971-979. PMID: 18067098
  14. Penne EL, Sergeyeva O. Sodium gradient: a tool to individualize dialysate sodium prescription in chronic hemodialysis patients? Blood Purif. 2011;31(1-3):86-91. PMID: 21228573
  15. Canaud B, Kooman J, Selby NM, et al. Sodium and water handling during hemodialysis: new pathophysiologic insights and management approaches for improving outcomes in end-stage kidney disease. Kidney Int. 2019;95(2):296-309. PMID: 30665570
  16. Hecking M, Karaboyas A, Saran R, et al. Dialysate sodium concentration and the association with interdialytic weight gain, hospitalization, and mortality. Clin J Am Soc Nephrol. 2012;7(1):92-100. PMID: 22052942
  17. Christa M, Smyth B, Mayne KJ, et al. Increased risk of cardiac death with cumulative exposure to fluid overload and dialysate sodium ≤138 mmol/l in hemodialysis patients. Clin Kidney J. 2025;18(10):sfaf259. PMID: 41133181
  18. Marshall MR, Vandal AC, de Zoysa JR, et al. Effect of low-sodium versus conventional sodium dialysate on left ventricular mass in home and self-care satellite facility hemodialysis patients: a randomized clinical trial. J Am Soc Nephrol. 2020;31(5):1078-1091. PMID: 32188697
  19. Iatridi F, Malandris K, Ekart R, et al. Low dialysate sodium and 48-h ambulatory blood pressure in patients with intradialytic hypertension: a randomized crossover study. Nephrol Dial Transplant. 2024;39(11):1900-1910. PMID: 38710537
  20. Varda L, Piko N, Bevc S, Hojs R, Ekart R. Effect of different dialysate sodium concentrations on blood pressure in chronic haemodialysis patients: a randomized study. Blood Purif. 2025;54(9-10):576-589. PMID: 40609518
  21. Ertuglu LA, Dilaver RG, Gamboa J, et al. Randomized crossover trial of low sodium dialysate on tissue sodium accumulation in hemodialysis. Kidney Int Rep. 2026;11(8):106581. PMID: 42404870
  22. de Paula FM, Peixoto AJ, Pinto LV, et al. Clinical consequences of an individualized dialysate sodium prescription in hemodialysis patients. Kidney Int. 2004;66(3):1232-1238. PMID: 15327422
  23. Petitclerc T. Prescribing dialysate sodium in maintenance hemodialysis patients: what can conductivity monitoring contribute? Blood Purif. 2026;55(2):156-160. PMID: 41108713
  24. Oliver MJ, Edwards LJ, Churchill DN. Impact of sodium and ultrafiltration profiling on hemodialysis-related symptoms. J Am Soc Nephrol. 2001;12(1):151-156. PMID: 11134261
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  26. Dhrolia MF, Akhtar SF, Ahmed E, Naqvi A, Rizvi A. Azotemia protects the brain from osmotic demyelination on rapid correction of hyponatremia. Saudi J Kidney Dis Transpl. 2014;25(3):558-566. PMID: 24821152
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