What is the treatment approach for hyponatremia?

Treatment Approach for Hyponatremia

The treatment of hyponatremia should be tailored to the patient's volume status (hypovolemic, euvolemic, or hypervolemic) with careful attention to correction rates not exceeding 8-10 mEq/L in the first 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

• Classify hyponatremia by severity:

  • Mild: 130-135 mEq/L
  • Moderate: 125-129 mEq/L
  • Severe: <125 mEq/L 1

• Determine volume status:

  • Hypovolemic: Signs of dehydration, orthostatic hypotension
  • Euvolemic: No edema or signs of dehydration
  • Hypervolemic: Edema, ascites, pulmonary congestion 1, 2

Treatment Algorithm Based on Volume Status

Hypovolemic Hyponatremia

1. First-line: Fluid resuscitation with isotonic saline or 5% albumin 1
2. Second-line: Discontinue diuretics if applicable 1
3. Monitor serum sodium every 2-4 hours during active correction 1

Euvolemic Hyponatremia (e.g., SIADH)

1. First-line: Fluid restriction (<1-1.5 L/day) 1, 3
2. Second-line options:
   • Ensure adequate solute intake (salt and protein) 1, 3
   • Consider vasopressin receptor antagonists (vaptans) in hospital setting 1, 4
   • Urea may be considered as an effective second-line therapy 3

Hypervolemic Hyponatremia

1. First-line: Fluid restriction (<1 L/day) 1
2. Second-line: Loop diuretics with careful monitoring 1
3. Consider tolvaptan for clinically significant hypervolemic hyponatremia, but must be initiated in hospital setting and limited to 30 days due to liver injury risk 1, 4

Management of Severe Symptomatic Hyponatremia

• For patients with severe symptoms (seizures, altered consciousness):
  • Administer hypertonic saline (3%) with initial bolus to increase sodium by 4-6 mEq/L within 1-2 hours 1, 2, 5
  • Rapid intermittent administration of hypertonic saline is preferred over continuous infusion 3
  • Target correction rate: 0.5-1 mmol/L/hour initially 1

Critical Monitoring Parameters

• Target correction rates:

  • Not to exceed 8-10 mmol/L in 24 hours 1
  • Not to exceed 18 mmol/L in 48 hours 1
  • More cautious correction (4-6 mmol/L/day) for high-risk patients (liver disease, alcoholism, malnutrition, hypokalemia, chronic hyponatremia) 1

• Monitor serum sodium levels every 2-4 hours during active correction 1

Complications and Precautions

• Watch for osmotic demyelination syndrome (ODS) signs:

  • Dysarthria, dysphagia, altered mental status, quadriparesis 1

• If correction is too rapid:

  • Stop therapy immediately
  • Consider administering hypotonic fluids and/or desmopressin to re-lower sodium 1, 3

Medication-Specific Considerations

• Tolvaptan (Vaptan):

  • Effective for euvolemic or hypervolemic hyponatremia 4
  • FDA-approved data shows significant increases in serum sodium levels compared to placebo 4
  • Must be initiated in hospital setting with close monitoring 4
  • Limited to 30 days due to risk of liver injury 1, 4
  • Contraindicated with strong CYP3A inhibitors 4
  • Common side effects: thirst, dry mouth, polyuria 4

• Kayexalate:

  • Contains significant sodium which can affect correction calculations 1
  • Monitor for hyperkalemia reversal 1

• Potassium supplementation:

  • Administer via calibrated infusion device at controlled rate 1
  • Central line placement recommended for high-concentration solutions 1

Special Populations

• Women and elderly patients are more sensitive to hyponatremic injury 1
• Postoperative patients, particularly after pituitary surgery, are at higher risk 1
• Patients with cirrhosis on tolvaptan have increased risk of gastrointestinal bleeding (10% vs 2% with placebo) 4