How is hyponatremia (low sodium levels) treated?

Treatment of Hyponatremia

The treatment of hyponatremia should be tailored to the type of hyponatremia (hypovolemic, euvolemic, or hypervolemic) and severity of symptoms, with fluid restriction of 1-1.5 L/day being the cornerstone therapy for hypervolemic hyponatremia when serum sodium is below 125 mmol/L. 1

Classification and Initial Assessment

• Hyponatremia is defined as serum sodium concentration <135 mmol/L, with treatment generally considered when levels fall below 130 mmol/L 1
• Classification based on volume status is essential for appropriate management:
  • Hypovolemic hyponatremia: Caused by fluid losses (often from excessive diuretic use)
  • Euvolemic hyponatremia: Often due to SIADH (Syndrome of Inappropriate Antidiuretic Hormone)
  • Hypervolemic hyponatremia: Associated with conditions like cirrhosis, heart failure 1

Treatment Based on Type and Severity

Hypovolemic Hyponatremia

• Discontinue diuretics if they are the cause 1
• Administer sodium (normal saline) to restore plasma volume 1
• Identify and correct other causes of dehydration 1

Hypervolemic Hyponatremia (common in cirrhosis)

• Fluid restriction to 1-1.5 L/day when serum sodium <125 mmol/L 1
• Moderate salt restriction with daily intake of no more than 5-6.5g (87-113 mmol sodium) 1
• Consider albumin infusion which may improve serum sodium concentration 1
• Diuretic therapy with spironolactone (starting at 100 mg, up to 400 mg) and furosemide (starting at 40 mg, up to 160 mg) for patients with ascites 1

Severe Symptomatic Hyponatremia (any type)

• Hypertonic sodium chloride (3%) should be reserved for severely symptomatic patients with acute hyponatremia 1
• Serum sodium should be corrected slowly to avoid osmotic demyelination syndrome 1
• Target correction rate: no more than 8-10 mmol/L per day 1
• Close monitoring of serum sodium levels during correction is essential 1

Pharmacological Options

Vaptans (V2-receptor antagonists)

• Effective for hypervolemic hyponatremia by enhancing solute-free water excretion 1
• Tolvaptan has shown efficacy in clinical trials for treating hyponatremia in cirrhosis, heart failure, and SIADH 2
• Treatment should be initiated in hospital with close monitoring 1
• Caution in patients with liver disease due to potential liver toxicity 1
• Reduces need for fluid restriction compared to placebo (14% vs 25%) 2

Diuretics

• For hypervolemic hyponatremia, diuretics should be used cautiously 1
• If hypovolemic hyponatremia develops during diuretic therapy, discontinue diuretics and expand plasma volume with normal saline 1
• Spironolactone is preferred for initial management of ascites in cirrhosis 1

Special Considerations and Pitfalls

• Avoid overly rapid correction: Increasing serum sodium by >10 mmol/L within 24 hours risks osmotic demyelination syndrome 1
• Chronic hyponatremia: Requires slower correction than acute hyponatremia 1, 3
• Liver cirrhosis: Hyponatremia is associated with poor prognosis and increased risk of complications including hepatorenal syndrome 1
• Fluid restriction efficacy: While commonly recommended, fluid restriction alone is often insufficient to correct serum sodium but may prevent further decreases 1
• Monitoring: Frequent assessment of serum sodium, especially during the first 24-48 hours of treatment 1

Algorithm for Management

1. Determine type of hyponatremia (hypovolemic, euvolemic, hypervolemic) 1
2. Assess symptom severity (mild: nausea, headache; severe: seizures, altered consciousness) 3, 4
3. For severe symptoms: Administer 3% hypertonic saline with target increase of 4-6 mmol/L in first few hours 1
4. For hypovolemic hyponatremia: Administer normal saline and address underlying cause 1
5. For hypervolemic hyponatremia: Implement fluid restriction (1-1.5 L/day) if sodium <125 mmol/L 1
6. Consider vaptans for persistent hypervolemic or euvolemic hyponatremia not responding to conventional therapy 2
7. Monitor serum sodium every 4-6 hours during active correction to prevent overcorrection 1

Hyponatremia is associated with increased mortality and morbidity, particularly in patients with cirrhosis, making proper management crucial for improving patient outcomes 1, 3.