What are the criteria for prescribing sodium (Na) in hemodialysis patients?

Dialysate Sodium Prescription Criteria in Hemodialysis

Prescribe a dialysate sodium concentration of 135-138 mEq/L for most hemodialysis patients, avoiding concentrations ≥140 mEq/L, and do not use sodium profiling or individualize based on serum sodium levels. 1, 2

Standard Dialysate Sodium Concentration

The target dialysate sodium should be 135-138 mEq/L for maintenance hemodialysis patients. 2 This recommendation is based on:

• Avoiding high dialysate sodium (≥140 mEq/L) is critical, as concentrations at or above this threshold increase thirst, interdialytic weight gain, hypertension, and cardiovascular workload. 1, 2, 3
• The KDOQI guidelines explicitly state that increasing positive sodium balance by using high dialysate sodium concentration should be avoided (Grade B recommendation). 1, 3
• Recent large observational data from 68,196 patients across 25 countries showed that dialysate sodium ≤138 mmol/L was associated with higher mortality (HR 1.57), challenging older assumptions about lower being better. 4

Sodium Profiling Should Be Avoided

Do not use sodium profiling (starting with hypertonic dialysate and decreasing during treatment). 1, 2, 3

• Sodium profiling produces sodium loading, hypervolemia, increased thirst, and greater interdialytic weight gain. 3
• The DOPPS mortality data demonstrates that routine sodium profiling is associated with increased all-cause mortality. 3
• Sodium profiling starting with 145-155 mEq/L would dramatically accelerate sodium correction in hyponatremic patients, risking osmotic demyelination syndrome. 2

Do Not Individualize Based on Serum Sodium

Avoid the practice of aligning dialysate sodium to each patient's serum sodium concentration. 5, 6

• In patients with pre-dialysis serum sodium higher than dialysate sodium, increasing dialysate sodium to match serum levels significantly increased interdialytic weight gain (2.0 kg vs 2.3 kg, P=0.008) and thirst scores (P=0.015). 5
• Hypertonic dialysate prescriptions predispose to positive sodium balance and lead to higher blood pressure and increased interdialytic weight gain. 6
• Most dialysis centers (78.6%) appropriately use a standardized concentration rather than individualized prescriptions. 4

Dietary Sodium Restriction Is Mandatory

Prescribe dietary sodium restriction to ≤5g sodium chloride (2.0g or 85 mmol sodium) daily as an essential component of volume management. 1

• More stringent restriction to 2.5-3.8g sodium chloride (1-1.5g or 43-65 mmol sodium) daily is recommended for hypertensive dialysis patients. 1
• A 5g sodium chloride diet in a 70kg anuric compliant patient should result in approximately 1.5kg average interdialytic weight gain on thrice-weekly dialysis. 1
• Interdialytic weight gain exceeding 4.8% of body weight (3.4kg in a 70kg person) is associated with increased mortality when adjusted for comorbidity. 1, 3

Special Circumstances Requiring Modification

Severe Hyponatremia (Serum Na <120 mEq/L)

In patients with severe hyponatremia, temporarily reduce dialysate sodium below the standard 135-138 mEq/L range to prevent osmotic demyelination syndrome. 2

• Target sodium correction rate of 4-6 mEq/L per 24 hours, not exceeding 8 mEq/L per 24 hours in high-risk patients. 2
• Monitor for neurological symptoms including confusion, seizures, or altered consciousness. 2
• Minimize ultrafiltration volume during initial sessions, as aggressive fluid removal combined with sodium diffusion accelerates correction. 2

Chronic Intradialytic Hypotension

For chronically hypotensive patients, increase dialysis time rather than increasing dialysate sodium. 1

• Consider cooling dialysate temperature to 0.5°C below body temperature for hemodynamic stability. 3
• Isothermic hemodialysis reduced intradialytic morbid events by 25% compared to standard approaches. 3
• Evaluate for transition to peritoneal dialysis, as these patients may tolerate PD better than HD. 1

Ultrafiltration Rate Considerations

Prescribe ultrafiltration rates that balance achieving euvolemia with hemodynamic stability, considering intradialytic hemodynamics, comorbidities, and symptoms on a treatment-by-treatment basis. 1

• Lower ultrafiltration rates by increasing HD time and/or decreasing interdialytic weight gain rather than compromising sodium removal. 1
• For patients with residual kidney function <2 mL/min, prescribe a minimum of 3 hours per session. 1
• Consider longer treatment times (>4 hours) or increased frequency (>3 sessions weekly) for patients with large weight gains, high ultrafiltration rates, or poorly controlled blood pressure. 1, 7

Common Pitfalls to Avoid

• Never assume that matching dialysate sodium to serum sodium improves outcomes—this practice worsens thirst and weight gain in hemodynamically stable patients. 5
• Do not implement routine blood volume monitoring or sodium profiling based on older literature, as high-quality trials show harm. 3
• Avoid relying solely on ultrafiltration without addressing dietary sodium intake, as sodium restriction is equally important for volume control. 1, 7
• Do not use dialysate sodium ≥140 mEq/L routinely, even in hypotensive patients, as the cardiovascular risks outweigh hemodynamic benefits. 1, 2, 3

Monitoring Requirements

Monitor interdialytic weight gain patterns as these reflect sodium and water balance between sessions. 2

• Implement systematic monitoring for missed or shortened treatments, as these predict mortality and recurrent complications. 7
• Reassess dry weight systematically to achieve true euvolemia. 7
• In patients with residual kidney function, measure Kru periodically to avoid inadequate dialysis when reducing dialysis dose. 1