What is the role of dialysis in treating hyponatremia (low sodium levels)?

From the Guidelines

Dialysis should be considered for patients with severe hyponatremia (sodium <120 mEq/L) who are symptomatic or unresponsive to other therapies, with a correction rate not exceeding 8-10 mEq/L in 24 hours to prevent osmotic demyelination syndrome. For patients with hyponatremia, particularly those with cirrhosis and ascites, the management depends on the etiology, chronicity, severity, and urgency of the condition 1. In cases of acute hyponatremia, rapid correction can be performed without concern for osmotic demyelination syndrome, whereas chronic hyponatremia requires more gradual correction to avoid overcorrection and mitigate the risk of osmotic demyelination syndrome.

Treatment Approaches

• For hypovolemic hyponatremia, treatment involves discontinuation of diuretics and/or laxatives and providing fluid resuscitation, typically with 5% IV albumin or crystalloid solution 1.
• For hypervolemic hyponatremia, treatment includes fluid restriction, reduction or discontinuation of diuretics and laxatives, administration of hyperoncotic albumin, and/or vasopressin receptor antagonists (“vaptans”) 1.
• Dialysis, including hemodialysis and continuous renal replacement therapy (CRRT), can be effective for severe or symptomatic hyponatremia, especially when other treatments are ineffective or contraindicated 1.

Dialysis Considerations

• Hemodialysis using a low-sodium dialysate can provide controlled sodium correction, with monitoring of serum sodium levels every 2-4 hours initially to ensure appropriate correction rates.
• The dialysis prescription should be adjusted based on the patient's volume status, with hypovolemic patients potentially needing volume replacement and hypervolemic patients benefiting from ultrafiltration.
• Maintenance dialysis may be necessary after initial correction, depending on the underlying cause of hyponatremia and residual kidney function.

Recent Guidance

The 2021 practice guidance by the American Association for the Study of Liver Diseases emphasizes the importance of tailored treatment approaches for hyponatremia in patients with cirrhosis and ascites, considering the etiology, chronicity, severity, and urgency of the condition 1. This guidance supports the use of dialysis as a treatment option for severe or symptomatic hyponatremia, particularly when other therapies are ineffective or contraindicated.

From the FDA Drug Label

In two double-blind, placebo-controlled, multi-center studies (SALT-1 and SALT-2), a total of 424 patients with euvolemic or hypervolemic hyponatremia (serum sodium <135 mEq/L) resulting from a variety of underlying causes (heart failure, liver cirrhosis, syndrome of inappropriate antidiuretic hormone [SIADH] and others) were treated for 30 days with tolvaptan or placebo, then followed for an additional 7 days after withdrawal.

The FDA drug label does not answer the question about dialysis for hyponatremia.

From the Research

Hyponatremia and Dialysis

• Hyponatremia is a common electrolyte disorder that can be managed with dialysis in some cases 2.
• The use of low-sodium dialysate and replacement fluids can provide a controlled rate of correction of plasma sodium concentration in patients with severe hyponatremia undergoing continuous renal replacement therapy (CRRT) 3.
• However, overly rapid correction of chronic hyponatremia can lead to osmotic demyelination syndrome, a rare but severe neurological condition 4, 5.
• Osmotic demyelination syndrome can occur even with correction rates ≤10 mEq/L in 24 hours, especially in patients with severe hyponatremia and high-risk features such as alcohol use disorder, hypokalemia, liver disease, and malnutrition 4.
• In patients with end-stage kidney disease, urgent start hemodialysis can also lead to osmotic demyelination syndrome, even in the absence of hyponatremia 5.

Risk Factors and Prevention

• Risk factors for osmotic demyelination syndrome include severe hyponatremia, rapid correction of serum sodium, and underlying conditions such as alcohol use disorder, hypokalemia, liver disease, and malnutrition 4, 5.
• Limiting serum sodium correction to <8 mEq/L in patients with severe hyponatremia and high-risk features can help prevent osmotic demyelination syndrome 4.
• Thiamine supplementation is also recommended for patients with hyponatremia and poor dietary intake 4.
• The use of low-sodium dialysate and replacement fluids can help prevent overly rapid correction of plasma sodium concentration in patients with severe hyponatremia undergoing CRRT 3.

Clinical Outcomes

• Osmotic demyelination syndrome is a rare but potentially devastating complication of hyponatremia, with a mortality rate of 19% and significant residual neurologic deficits in survivors 4, 6.
• The overall incidence of osmotic demyelination syndrome in patients with hyponatremia is estimated to be around 0.05% 6.
• Rapid correction of serum sodium is common in patients with hyponatremia, but osmotic demyelination syndrome is rare, suggesting that other factors may contribute to the development of this condition 6.