How is hyponatremia managed?

Management of Hyponatremia

The management of hyponatremia should be tailored to the underlying volume status (hypovolemic, euvolemic, or hypervolemic) and severity of symptoms, with treatment initiated when serum sodium is lower than 130 mmol/L. 1

Classification and Assessment

Hyponatremia is defined as serum sodium concentration below 135 mmol/L, though treatment is generally considered when levels fall below 130 mmol/L 1, 2. It is crucial to categorize hyponatremia based on volume status:

• Hypovolemic hyponatremia:

  • Clinical signs: Orthostatic hypotension, tachycardia, dry mucous membranes
  • Lab findings: Urine sodium typically <20 mEq/L (unless on diuretics)
  • Common causes: Excessive diuretic use, gastrointestinal losses

• Euvolemic hyponatremia:

  • Clinical signs: No signs of volume depletion or excess
  • Lab findings: Urine sodium >20-40 mEq/L, urine osmolality >500 mOsm/kg (in SIADH)
  • Common causes: SIADH, medications, endocrine disorders

• Hypervolemic hyponatremia:

  • Clinical signs: Edema, ascites, elevated jugular venous pressure
  • Lab findings: Urine sodium typically <20 mEq/L in heart failure or cirrhosis
  • Common causes: Cirrhosis, heart failure, renal disease

Treatment Algorithm

1. Hypovolemic Hyponatremia

• Primary treatment: Plasma volume expansion with isotonic (0.9%) saline solution 1, 2
• Correct the underlying cause (e.g., stop diuretics if appropriate)
• Monitor serum sodium levels closely during correction

2. Euvolemic Hyponatremia

• Primary treatment: Fluid restriction (1-1.5 L/day) 1, 2
• Discontinue medications that may cause hyponatremia (e.g., SSRIs, carbamazepine)
• For SIADH:
  • Salt tablets or urea may be considered for persistent cases 2
  • Vaptans (e.g., tolvaptan) can be considered for short-term use (≤30 days) in refractory cases 1, 2, 3

3. Hypervolemic Hyponatremia

• Primary treatment: Fluid restriction and management of underlying condition 1
• For cirrhosis:
  • Spironolactone (100-400 mg/day) with furosemide (40-160 mg/day) in a 100:40 ratio 1
  • Albumin infusion may improve serum sodium concentration in severe cases 1
• For heart failure:
  • Loop diuretics with careful monitoring 2
  • Maintain serum potassium in the 4.5-5.0 mEq/L range 2

4. Severe Symptomatic Hyponatremia (regardless of etiology)

• Emergency treatment: Hypertonic (3%) saline administration 1, 2
• Initial correction: 5 mmol/L in the first hour for severe symptoms 1
• Maximum correction rate: 8 mmol/L per 24 hours to avoid central pontine myelinolysis 1, 2, 4
• Monitor serum sodium every 2-4 hours during active correction 2

Important Considerations and Pitfalls

Correction Rate

• Critical pitfall: Overly rapid correction can lead to osmotic demyelination syndrome (central pontine myelinolysis) 1, 2, 4
• Signs of osmotic demyelination: Dysarthria, dysphagia, altered mental status, quadriparesis
• If correction exceeds 8 mmol/L in 24 hours, consider administration of hypotonic fluids or desmopressin 2, 5

Vaptans

• Vaptans can effectively improve serum sodium in 45-82% of cases with cirrhosis 1
• Safety concerns: Only established for short-term treatments (1 week to 1 month) 1
• Long-term use of satavaptan has been associated with higher mortality 1
• Tolvaptan may have limited efficacy in severe hyponatremia (≤125 mEq/L) in real-life settings 1

Electrolyte Balance

• Correct hypokalemia concurrently as it affects sodium balance 2
• Potassium depletion causes sodium retention in the kidneys 2

Chronic Asymptomatic Hyponatremia

• Chronic hyponatremia is associated with cognitive impairment, gait disturbances, increased falls and fractures 4
• Even mild chronic hyponatremia should be addressed to prevent these complications

By following this structured approach based on volume status and symptom severity, clinicians can effectively manage hyponatremia while minimizing the risk of complications from both the condition itself and its treatment.