How should hyponatremia be managed in an adult with end‑stage renal disease (ESRD) on dialysis?

Management of Hyponatremia in ESRD Patients on Dialysis

For ESRD patients on dialysis with severe hyponatremia (serum sodium <125 mEq/L), use conventional hemodialysis with a low dialysate sodium concentration (128-130 mEq/L) and reduced blood flow rate (50-100 mL/min) to achieve controlled sodium correction of 1-2 mEq/L per hour, avoiding the risk of osmotic demyelination syndrome while simultaneously addressing uremia and volume overload. 1, 2

Initial Assessment and Severity Classification

Before initiating treatment, determine the severity and symptom profile:

• Severe hyponatremia: Serum sodium <125 mEq/L 3, 4
• Moderate hyponatremia: Serum sodium 125-129 mEq/L 3
• Mild hyponatremia: Serum sodium 130-134 mEq/L 3

Assess for severe neurological symptoms including delirium, confusion, impaired consciousness, ataxia, seizures, or coma, which constitute medical emergencies. 3, 4 Even mild chronic hyponatremia increases fall risk, fracture rates, and mortality in dialysis patients. 4

Dialysis-Based Correction Strategy

For Severe Hyponatremia (Na <125 mEq/L) Requiring Urgent Dialysis

Primary approach: Use modified hemodialysis parameters rather than hypertonic saline in ESRD patients who require both sodium correction and dialysis. 1, 2

Dialysis prescription modifications:

• Set dialysate sodium concentration to 128-130 mEq/L (the lowest permissible level on conventional HD machines) 1, 2
• Initiate blood flow at 50 mL/min during the first session to achieve sodium correction of approximately 1 mEq/L per hour 1, 2
• Increase blood flow to 100 mL/min in subsequent sessions if tolerated, achieving sodium correction of approximately 2 mEq/L per hour 1
• Target total sodium correction of no more than 10-12 mEq/L in the first 24 hours to prevent osmotic demyelination syndrome 4, 2

This approach allows simultaneous correction of uremia, volume overload, and hyponatremia while maintaining safe sodium correction rates. 1, 2

Monitoring During Dialysis

• Check serum sodium hourly during the first dialysis session to ensure correction rate remains at 1-2 mEq/L per hour 1, 2
• Adjust blood flow rate if sodium rises too rapidly 2
• Continue monitoring every 2-4 hours during subsequent sessions until sodium stabilizes above 125 mEq/L 1

Critical Safety Considerations

Avoiding Osmotic Demyelination Syndrome

The most serious complication of overly rapid sodium correction is osmotic demyelination syndrome, which can cause parkinsonism, quadriparesis, or death. 4 This risk is particularly elevated when:

• Sodium increases by more than 10-12 mEq/L in 24 hours 4, 2
• Sodium increases by more than 18 mEq/L in 48 hours 4
• Chronic hyponatremia (>48 hours duration) is corrected too rapidly 4

Key pitfall: Standard dialysate sodium concentrations (typically 140 mEq/L) will correct sodium far too rapidly in severely hyponatremic ESRD patients, potentially causing irreversible neurological damage. 1, 2

When Hypertonic Saline May Be Considered

If the ESRD patient presents with severely symptomatic hyponatremia (seizures, coma, cardiorespiratory distress) before dialysis can be initiated, consider bolus hypertonic saline (3%) to increase serum sodium by 4-6 mEq/L within 1-2 hours to reverse acute hyponatremic encephalopathy. 3, 4 However, transition to modified dialysis parameters as soon as feasible to maintain controlled correction. 1, 2

Addressing Underlying Causes

While correcting sodium, identify and treat contributing factors:

• Medication review: Perform comprehensive medication reconciliation to identify drugs causing hyponatremia (diuretics, SSRIs, carbamazepine, NSAIDs) 3
• Volume status assessment: Determine if patient is hypovolemic, euvolemic, or hypervolemic, though this distinction is less critical in ESRD patients requiring dialysis 3, 4
• Free water intake: Assess for excessive water consumption between dialysis sessions 5
• Residual kidney function: Evaluate whether any remaining urine output contributes to sodium handling 5

Interdialytic Management

After initial correction during dialysis:

• Fluid restriction: Limit free water intake between dialysis sessions, typically to 500-1000 mL/day depending on residual urine output 4, 6
• Dietary sodium: Ensure adequate dietary sodium intake (though excessive sodium increases interdialytic weight gain and hypertension) 5
• Dialysate sodium for maintenance: Once sodium normalizes, use standard dialysate sodium (typically 140 mEq/L) for subsequent treatments 5
• Avoid sodium profiling: Do not use sodium profiling techniques (high initial dialysate sodium with gradual decrease) as these can worsen thirst and interdialytic weight gain 5

Special Populations and Considerations

Patients with Residual Kidney Function

For ESRD patients with significant residual urine output (>100 mL/day), loop diuretics may assist with sodium and water management between dialysis sessions, though use with caution due to ototoxicity risk (particularly with furosemide; bumetanide has lower risk). 5

Chronic vs. Acute Hyponatremia

• Chronic hyponatremia (>48 hours): Requires slower correction to prevent osmotic demyelination; use the conservative approach with 50 mL/min blood flow initially 4, 2
• Acute hyponatremia (<48 hours): Can tolerate slightly faster correction, but still limit to 2 mEq/L per hour maximum in ESRD patients 3, 4

Alternative Modalities

Continuous renal replacement therapy (CRRT) is ideal for managing severe hyponatremia in ESRD patients as it allows precise, gradual sodium correction. 1 However, CRRT is often unavailable in resource-limited settings, making the modified conventional hemodialysis approach described above a practical alternative. 1

Peritoneal dialysis patients: If hyponatremia develops in PD patients, adjust PD prescription by reducing ultrafiltration volume (using less hypertonic glucose solutions or changing icodextrin to 1.5% glucose), and liberalize salt intake. 5

Common Pitfalls to Avoid

• Do not use standard dialysate sodium (140 mEq/L) in severely hyponatremic patients—this will correct sodium too rapidly 1, 2
• Do not delay dialysis in uremic patients with severe hyponatremia out of fear of rapid correction—use modified parameters instead 1
• Do not rely solely on fluid restriction in ESRD patients requiring dialysis for uremia 1
• Do not use vaptans (vasopressin receptor antagonists) in ESRD patients, as these are contraindicated due to unpredictable effects and risk of overly rapid correction 4
• Do not forget medication reconciliation at every transition of care to identify causative medications 3