What is the treatment approach for hyponatremia (low sodium levels)?

Treatment of Hyponatremia

The treatment of hyponatremia must be tailored to the underlying cause, severity, chronicity, and volume status of the patient, with fluid restriction being the first-line approach for most cases of mild to moderate hyponatremia. 1

Classification and Assessment

Severity Classification:

• Mild: 130-134 mmol/L
• Moderate: 125-129 mmol/L
• Severe: <125 mmol/L 1

Volume Status Assessment:

• Hypovolemic: Signs of dehydration, orthostatic hypotension
• Euvolemic: No signs of volume depletion or overload
• Hypervolemic: Edema, ascites, signs of fluid overload 1

Treatment Algorithm Based on Volume Status

1. Hypovolemic Hyponatremia:

• Discontinue diuretics and/or laxatives if applicable
• Provide fluid resuscitation with:
  • 5% IV albumin (preferred in cirrhosis)
  • Isotonic (0.9%) saline for volume expansion 2, 1

2. Euvolemic Hyponatremia:

• Identify and treat underlying cause (medications, SIADH, hypothyroidism, adrenal insufficiency)
• Fluid restriction (1-1.5 L/day) 1
• For SIADH:
  • Ensure adequate solute intake (salt and protein)
  • Consider vasopressin receptor antagonists (vaptans) for persistent cases 1, 3
  • Urea may be an effective alternative treatment 4

3. Hypervolemic Hyponatremia:

• Fluid restriction (1-1.5 L/day)
• Sodium restriction (5-6.5 g/day)
• Diuretic therapy (spironolactone and furosemide) as needed
• For cirrhotic patients:
  • Moderate hyponatremia (120-125 mEq/L): Fluid restriction to 1,000 mL/day
  • Severe hyponatremia (<120 mEq/L): More severe fluid restriction plus albumin infusion 2
• Consider vasopressin receptor antagonists in selected cases 1, 3

Management of Symptomatic Hyponatremia

Severe Symptomatic Hyponatremia (seizures, coma, cardiorespiratory distress):

• Administer 3% hypertonic saline (100-150 mL bolus or infusion)
• Target initial correction: 4-6 mEq/L in first 1-2 hours 1, 5
• Maximum correction limits:
  • 8-10 mEq/L in 24 hours
  • 18 mEq/L in 48 hours 1, 6
• Monitor serum sodium every 2-4 hours during active correction 1

Mild to Moderate Symptomatic Hyponatremia:

• Fluid restriction as first-line treatment
• Address underlying cause
• Consider vasopressin receptor antagonists for euvolemic or hypervolemic cases 3

Critical Considerations

Avoiding Osmotic Demyelination Syndrome (ODS):

• Avoid overly rapid correction of chronic hyponatremia
• Risk factors for ODS: Advanced liver disease, alcoholism, severe hyponatremia, malnutrition, hypokalemia, hypophosphatemia, hypoglycemia, low cholesterol, prior encephalopathy 2
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 2, 4

Efficacy of Vasopressin Receptor Antagonists:

• Tolvaptan has been shown to effectively increase serum sodium levels in patients with euvolemic or hypervolemic hyponatremia 3
• Vaptans improve serum sodium in 45-82% of cirrhotic patients with hyponatremia 1
• Monitor for potential side effects including overly rapid correction of hyponatremia and increased thirst 1

Special Populations

Cirrhotic Patients:

• Hyponatremia reflects worsening hemodynamic status and is associated with increased risk of complications (hepatic encephalopathy, hepatorenal syndrome, spontaneous bacterial peritonitis) 2
• Albumin infusion has shown benefit in improving hyponatremia in hospitalized cirrhotic patients 2
• Avoid indiscriminate use of hypertonic saline as it can worsen ascites and edema 1

Acute vs. Chronic Hyponatremia:

• Acute hyponatremia (onset within 48 hours): Can be corrected more rapidly to prevent cerebral edema
• Chronic hyponatremia: Requires gradual correction to avoid ODS 2

By following this structured approach based on volume status, symptom severity, and chronicity, clinicians can effectively manage hyponatremia while minimizing the risk of complications such as osmotic demyelination syndrome.