How to manage a patient with hyponatremia (low sodium level) and decreased serum osmolality?

From the Guidelines

The patient with sodium 129 and serum osmolality 275 should be managed with fluid restriction to 1,000 mL/day, as this is a case of mild to moderate hyponatremia. According to the most recent and highest quality study 1, mild hyponatremia (Na 126-135 mEq/L) in cirrhosis without symptoms does not require specific management apart from monitoring and water restriction.

Assessment and Management

To manage this patient, first assess the volume status to determine if the patient is hypovolemic, euvolemic, or hypervolemic.

• For hypovolemic hyponatremia, administer isotonic saline (0.9% NaCl) at 100-150 mL/hour until euvolemia is achieved.
• For euvolemic hyponatremia, fluid restriction to 800-1000 mL/day is the mainstay of treatment, with consideration of 3% hypertonic saline for severe symptoms (1-2 mL/kg/hour).
• For hypervolemic hyponatremia, restrict fluid and sodium intake and administer loop diuretics like furosemide 20-40 mg IV.

Correction Rate

In all cases, sodium correction should not exceed 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome, as recommended by 1. For patients with severe hyponatremia, the use of hypertonic saline is reserved for short-term treatment of patients with symptomatic or severe hyponatremia or those with imminent liver transplant.

Monitoring and Medications

Monitor serum sodium every 2-4 hours during active correction. Discontinue medications that may cause hyponatremia, such as thiazide diuretics, SSRIs, or carbamazepine. The cautious correction rate is crucial because rapid correction can lead to permanent neurological damage, while inadequate treatment of severe hyponatremia can result in cerebral edema, seizures, and death.

Additional Considerations

As noted in 1, hypertonic sodium chloride administration may improve hyponatremia at the cost of worsening fluid overload, and is best reserved for those with severely symptomatic acute hyponatremia, especially if a transplant is imminent. The goal is to increase serum sodium by up to 5 mmol/L in the first hour, with a limit of 8-10 mmol/L every 24 hours thereafter, until the serum sodium concentration reaches 130 mmol/L.

From the FDA Drug Label

Patients should be in a hospital for initiation and re-initiation of therapy to evaluate the therapeutic response and because too rapid correction of hyponatremia can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death The usual starting dose for tolvaptan tablets is 15 mg administered once daily without regard to meals. Increase the dose to 30 mg once daily, after at least 24 hours, to a maximum of 60 mg once daily, as needed to achieve the desired level of serum sodium.

To manage a patient with hyponatremia (low sodium level) and decreased serum osmolality, the patient should be hospitalized for initiation and re-initiation of tolvaptan therapy. The usual starting dose is 15 mg once daily, which can be increased to 30 mg once daily after at least 24 hours, and up to a maximum of 60 mg once daily as needed to achieve the desired level of serum sodium.

• Key considerations:
  • Monitor serum electrolytes and volume frequently during initiation and titration
  • Avoid fluid restriction during the first 24 hours of therapy
  • Patients should be advised to continue ingestion of fluid in response to thirst
  • Monitor for changes in serum sodium and volume status after discontinuation of tolvaptan 2

From the Research

Management of Hyponatremia

The patient has a serum sodium level of 129 mEq/L, which is considered moderate hyponatremia 3. The serum osmolality is 275, which is decreased.

• The approach to managing hyponatremia should consist of treating the underlying cause 4.
• The patient should be categorized according to their fluid volume status (hypovolemic hyponatremia, euvolemic hyponatremia, or hypervolemic hyponatremia) 4, 3.
• For hypovolemic hyponatremia, treatment includes normal saline infusions 3.
• For euvolemic hyponatremia, treatment includes restricting free water consumption or using salt tablets or intravenous vaptans 3.
• For hypervolemic hyponatremia, treatment is primarily managing the underlying cause (e.g., heart failure, cirrhosis) and free water restriction 3.

Treatment of Symptomatic Hyponatremia

• Severely symptomatic hyponatremia (with signs of somnolence, obtundation, coma, seizures, or cardiorespiratory distress) is a medical emergency 4.
• US and European guidelines recommend treating severely symptomatic hyponatremia with bolus hypertonic saline to reverse hyponatremic encephalopathy by increasing the serum sodium level by 4 mEq/L to 6 mEq/L within 1 to 2 hours but by no more than 10 mEq/L (correction limit) within the first 24 hours 4.
• Overly rapid correction of chronic hyponatremia may cause osmotic demyelination, a rare but severe neurological condition, which can result in parkinsonism, quadriparesis, or even death 4, 5.

Use of Vasopressin Receptor Antagonists

• Vasopressin receptor antagonists, such as tolvaptan, can be effective in managing the syndrome of inappropriate antidiuresis and hyponatremia in patients with heart failure and cirrhosis 6.
• Tolvaptan is the only oral agent in this class approved for raising sodium levels in hypervolemic and euvolemic hyponatremia 6.
• Fluid restriction should be avoided during the first 24 h of treatment to prevent overly rapid correction of hyponatremia 6.