How to manage hyponatremia in patients with Chronic Kidney Disease (CKD) on hemodialysis?

Management of Hyponatremia in Hemodialysis Patients

The primary goal is preventing osmotic demyelination syndrome (ODS) by controlling the rate of sodium correction to 4-6 mEq/L per 24 hours, not exceeding 8-10 mEq/L in the first 24 hours, which requires careful manipulation of dialysate sodium concentration and blood flow rates during hemodialysis sessions. 1

Critical Safety Framework

The management of hyponatremia in hemodialysis patients fundamentally differs from other populations because conventional hemodialysis can rapidly correct sodium levels through diffusive transfer, creating substantial risk for ODS—a potentially fatal neurological complication causing dysarthria, mutism, dysphagia, lethargy, seizures, coma, or death. 2 The correction rate must not exceed 12 mEq/L per 24 hours, with slower rates advisable in high-risk patients including those with severe malnutrition, alcoholism, or advanced liver disease. 2

Immediate Dialysis Prescription Modifications

Dialysate Sodium Concentration

• Lower the dialysate sodium to 128-130 mEq/L (the lowest permissible level in most conventional HD machines) for patients with severe hyponatremia requiring urgent dialysis. 3, 4
• This approach allows controlled sodium correction while simultaneously addressing uremia and volume overload. 3
• Standard dialysate sodium concentrations of 135-140 mEq/L will cause excessively rapid sodium correction through diffusive transfer and must be avoided. 1

Blood Flow Rate Adjustment

• Initiate hemodialysis with blood flow rates of 50 mL/min to limit the rate of sodium transfer, which typically results in sodium correction of approximately 2 mEq/L per hour. 3, 4
• After the first session, if sodium correction remains within safe limits, blood flow can be cautiously increased to 100 mL/min, typically resulting in 2 mEq/L per hour correction. 4
• This stepwise approach allows precise control over correction rates while monitoring neurological status. 4

Ultrafiltration Management

• Minimize ultrafiltration volume during initial dialysis sessions, as aggressive fluid removal combined with sodium diffusion accelerates correction beyond safe limits. 1
• The combination of fluid removal and sodium diffusion creates additive effects on serum sodium concentration. 5

Alternative Modality for Severe Cases

Continuous venovenous hemofiltration (CVVH) with customized low-sodium replacement fluid represents the gold standard for severe hyponatremia (sodium <100 mEq/L) in dialysis patients, as it allows precise regulation of sodium correction rate through single-pool sodium kinetic modeling. 5 However, this modality requires specialized equipment and expertise not available in many centers. 4

When CVVH is unavailable, the modified conventional hemodialysis approach described above (low dialysate sodium + reduced blood flow) provides effective management in resource-limited settings. 4

Monitoring Requirements

• Measure serum sodium every 2-4 hours during initial dialysis sessions to ensure correction rates remain within safe limits. 1, 3
• Continuously assess neurological status for signs of ODS, including confusion, altered consciousness, or new neurological deficits. 1, 2
• If sodium rises too rapidly (>8 mEq/L in first 8 hours), discontinue or interrupt dialysis and consider administration of hypotonic fluid. 2

Long-Term Dialysate Sodium Strategy

Once acute hyponatremia is corrected:

• Maintain dialysate sodium at 135-138 mEq/L for ongoing treatments, as this range optimizes volume and blood pressure control without promoting excessive thirst or interdialytic weight gain. 1
• Avoid sustained use of dialysate sodium ≥140 mEq/L, which increases thirst, interdialytic weight gain, hypertension, and cardiovascular workload—effects that contribute to morbidity and mortality. 6, 1
• Sodium profiling (starting with hypertonic dialysate 145-155 mEq/L and gradually decreasing) should be discouraged as it produces similar adverse effects to sustained high dialysate sodium. 6, 1

Dietary Sodium Management

• Implement dietary sodium restriction to 2-3 g/day (85-100 mmol/day) to minimize interdialytic sodium accumulation and facilitate achievement of dry weight. 6, 1
• A 5-g sodium chloride diet in a 70 kg anuric patient should result in approximately 1.5 kg average interdialytic weight gain on conventional thrice-weekly regimen, which most patients can tolerate. 6
• Dietary sodium restriction is essential for volume and blood pressure control, directly impacting cardiovascular morbidity and mortality. 6

Common Pitfalls to Avoid

• Never use hypertonic saline in hyponatremic dialysis patients, as the combination with dialysis-mediated sodium correction creates unacceptable risk for overly rapid correction. 2
• Avoid fluid restriction during initial correction, as this paradoxically increases the likelihood of overly rapid correction; patients should continue fluid intake in response to thirst. 2
• Do not co-administer diuretics during acute correction, as this increases risk of too-rapid sodium correction and requires close monitoring if unavoidable. 2
• Avoid vaptans (tolvaptan) in dialysis patients, as these medications are contraindicated in anuric patients and can cause overly rapid correction. 2

Special Considerations for Hypervolemic Hyponatremia

Patients with volume overload and hyponatremia present the greatest challenge, as they require both sodium correction and fluid removal. 5 The modified hemodialysis approach (low dialysate sodium, reduced blood flow, limited ultrafiltration) addresses both issues while maintaining safe correction rates. 3, 4 This approach has successfully managed patients with sodium as low as 107-109 mEq/L, achieving complete resolution of uremic manifestations without neurological deficits. 4