What are the interventions for hyponatremia (low sodium)?

Management of Hyponatremia

Treatment of hyponatremia should be tailored to the underlying cause, with different approaches for hypovolemic, euvolemic, and hypervolemic hyponatremia, while carefully monitoring serum sodium to avoid overly rapid correction. 1

Classification and Assessment

Hyponatremia is defined as serum sodium concentration below 135 mmol/L, but treatment is generally considered when levels fall below 130 mmol/L 1. The approach to management depends on:

1. Volume status assessment:

   • Hypovolemic hyponatremia: Dehydration signs, history of fluid losses
   • Euvolemic hyponatremia: Normal volume status (often SIADH)
   • Hypervolemic hyponatremia: Edema, ascites (common in cirrhosis, heart failure)

2. Symptom severity:

   • Mild: Nausea, headache, weakness
   • Severe: Seizures, altered consciousness, respiratory distress

3. Chronicity: Acute (<48 hours) vs. chronic (>48 hours)

Treatment Algorithms by Type

1. Hypovolemic Hyponatremia

• First-line: Plasma volume expansion with normal saline solution 1
• Mechanism: Corrects the underlying volume depletion that triggers ADH release
• Implementation:
  • Identify and correct the causative factor (often excessive diuretic use)
  • Discontinue offending diuretics 1
  • Monitor serum sodium during correction

2. Euvolemic Hyponatremia (including SIADH)

• First-line: Fluid restriction to 1-1.5 L/day 1
• Second-line options:
  • Tolvaptan: For serum sodium <125 mEq/L or symptomatic hyponatremia resistant to fluid restriction 2
    • Starting dose: 15 mg once daily
    • May increase at intervals ≥24 hours to 30 mg once daily, maximum 60 mg daily
    • CAUTION: Must be initiated in hospital setting with close monitoring
    • Limited to 30 days due to liver injury risk 2
  • Urea: Can be effective but has poor palatability 3

3. Hypervolemic Hyponatremia (cirrhosis, heart failure)

• First-line: Attain negative water balance 1
  • Fluid restriction to 1-1.5 L/day 1
  • Salt restriction to 5-6.5g daily (87-113 mmol sodium) 1
• Second-line:
  • Diuretics: Spironolactone (starting 100 mg, up to 400 mg) with or without furosemide (starting 40 mg, up to 160 mg) 1
  • Tolvaptan: For refractory cases, with same precautions as above 2
  • Albumin infusion: May improve serum sodium concentration, but limited evidence 1

Management of Severe Symptomatic Hyponatremia

For life-threatening symptoms (seizures, coma, respiratory distress):

• Hypertonic saline (3%) 1, 4:
  • Initial goal: Increase serum sodium by 4-6 mEq/L in first 1-2 hours
  • Daily limit: Do not exceed 8-10 mEq/L in 24 hours
  • Rate: After initial correction, slow to prevent osmotic demyelination syndrome
  • Monitor: Check serum sodium every 2-4 hours during correction

Critical Safety Considerations

1. Avoid overly rapid correction: Risk of osmotic demyelination syndrome

   • Maximum correction: 8 mmol/L per day for chronic hyponatremia 1
   • Higher risk groups: Malnourished patients, alcoholics, advanced liver disease 2

2. Monitor for adverse effects:

   • With diuretics: Hypovolemia, worsening renal function, electrolyte disturbances 1
   • With tolvaptan: Liver injury, dehydration, hypernatremia 2

3. Contraindications:

   • Tolvaptan: ADPKD, inability to sense thirst, hypovolemic hyponatremia, anuria 2
   • Hypertonic saline in hypervolemic states: May worsen volume overload 1

Special Considerations in Cirrhosis

Hyponatremia in cirrhosis requires particular attention:

• Associated with increased mortality and morbidity 1
• Avoid hypertonic saline except in severe symptomatic cases as it worsens ascites and edema 1
• Vaptans can be effective short-term but have safety concerns with long-term use 1

By following these guidelines and carefully monitoring serum sodium levels during correction, the risks of both untreated hyponatremia and treatment complications can be minimized.