How is hyponatremia treated?

Treatment of Hyponatremia

The treatment of hyponatremia should be based on the underlying cause, severity of symptoms, and volume status, with careful attention to correction rates to avoid complications like osmotic demyelination syndrome. 1

Classification and Initial Assessment

Hyponatremia is classified based on:

1. Severity:

   • Mild: 130-134 mmol/L
   • Moderate: 125-129 mmol/L
   • Severe: <125 mmol/L 2

2. Volume status:

   • Hypovolemic (decreased total body sodium)
   • Euvolemic (normal total body sodium)
   • Hypervolemic (increased total body sodium) 3

3. Symptom severity:

   • Mild symptoms: nausea, headache, weakness, cognitive deficits
   • Severe symptoms: seizures, coma, altered mental status 2

Treatment Algorithm

1. Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with severe symptoms (seizures, coma, altered mental status):

• Administer 3% hypertonic saline as 100-150 mL bolus or continuous infusion 4
• Target correction rate: 4-6 mmol/L within first 6 hours or until severe symptoms resolve 1, 5
• Maximum correction: Do not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 3
• Monitoring: Check serum sodium every 2-4 hours during active correction 1

2. Hypovolemic Hyponatremia

• Administer isotonic (0.9%) saline to restore intravascular volume 3, 2
• Identify and address underlying cause (excessive diuretics, gastrointestinal losses) 6
• Monitor: Serum sodium, potassium, and renal function 3

3. Euvolemic Hyponatremia (SIADH)

• Fluid restriction of 500-1000 mL/day as first-line therapy 1, 3, 4
• Second-line options if fluid restriction fails:
  • Urea supplementation (effective and safe) 4
  • Tolvaptan (vasopressin receptor antagonist) for short-term use 3, 7
    • Initial dose: 15 mg once daily
    • Can be titrated up to 60 mg daily based on response
    • Shown to increase serum sodium in 45-82% of patients 1, 7
  • Salt tablets with high protein diet 1

4. Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Fluid restriction to 1-1.5 L/day 1, 3
• Sodium restriction (<2 g/day) 3
• Diuretics: Spironolactone (100-400 mg/day) with or without furosemide (40-160 mg/day) 3
• Consider tolvaptan for refractory cases, but use with caution in liver disease 1, 7

Special Considerations

Correction Rate Monitoring

• Target correction rate: Not to exceed 8-10 mmol/L in 24 hours 1, 3
• Risk factors for osmotic demyelination: chronic alcoholism, malnutrition, liver disease, hypokalemia 2
• If correction is too rapid, consider:
  • DDAVP (desmopressin) administration to prevent further water excretion 5
  • Hypotonic fluids to relower sodium if overcorrection occurs 4, 5

Neurosurgical Patients

Neurosurgical patients have a high prevalence of hyponatremia (up to 50%) and require special attention:

• Distinguish between SIADH and Cerebral Salt Wasting (CSW) 1
• For CSW, treatment includes:
  • 3% hypertonic saline for severe symptoms
  • Fludrocortisone for 7 days 1, 3
  • Normal saline if no response to above measures 1

Pitfalls and Caveats

1. Avoid overly rapid correction which can lead to osmotic demyelination syndrome, especially in chronic hyponatremia 1, 2

2. Do not withhold treatment in severely symptomatic patients while awaiting diagnostic workup 2

3. Fluid restriction alone is often ineffective in hypervolemic hyponatremia but may prevent further decreases in sodium 1

4. Monitor for complications of vaptans including thirst, dehydration, and hypernatremia; always initiate in hospital setting 1, 7

5. Recognize that even mild hyponatremia can cause cognitive impairment, gait disturbances, and increased risk of falls and fractures 2

By following this structured approach to the treatment of hyponatremia based on volume status and symptom severity, clinicians can effectively manage this common electrolyte disorder while minimizing the risk of complications.