What is the management of hyponatremia?

Management of Hyponatremia

The treatment of hyponatremia should be based on the severity of symptoms, volume status, and underlying cause, with correction rates not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2

Initial Assessment and Classification

• Hyponatremia is defined as serum sodium <135 mmol/L and should be further investigated when levels are <131 mmol/L 2, 1
• Initial workup should include serum and urine osmolarity, urine electrolytes, uric acid, and assessment of extracellular fluid volume status to determine the underlying cause 1
• Classify patients according to volume status: hypovolemic, euvolemic, or hypervolemic hyponatremia 1, 3

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (seizures, coma)

• Administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1, 4
• Do not exceed total correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
• Consider ICU admission for close monitoring during treatment 1
• Monitor serum sodium every 2 hours during initial correction 1

Mild to Moderate Symptomatic Hyponatremia

• Correction rate should not exceed 8 mmol/L in 24 hours 1, 2
• For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy, use more cautious correction (4-6 mmol/L per day) 1

Asymptomatic Hyponatremia

• Treatment approach depends on volume status and underlying cause 1, 3
• Correction should still not exceed 8 mmol/L in 24 hours 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1, 3
• Once euvolemia is achieved, reassess sodium levels and adjust treatment accordingly 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1L/day is the cornerstone of treatment for mild/asymptomatic cases 1, 2
• Consider pharmacological options for resistant cases 1:
  • Urea 2, 1
  • Diuretics 2, 1
  • Lithium 2, 1
  • Demeclocycline 2, 1
  • Vasopressin receptor antagonists (tolvaptan) for severe cases 1, 5

Hypervolemic Hyponatremia (e.g., cirrhosis, heart failure)

• Fluid restriction to 1000-1500 mL/day for moderate hyponatremia (Na <125 mmol/L) 1
• More severe fluid restriction plus albumin infusion for severe hyponatremia 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1

Special Considerations for Neurosurgical Patients

• Cerebral salt wasting (CSW) should be treated with replacement of sodium and intravenous fluids, not fluid restriction 2, 1
• Fludrocortisone may be considered in the treatment of hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm 2
• Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients 2
• Hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm should not be treated with fluid restriction 2, 1

Pharmacological Interventions

Vasopressin Receptor Antagonists (Vaptans)

• Consider for euvolemic or hypervolemic hyponatremia resistant to conventional therapy 1, 5
• Tolvaptan (oral) starting dose is 15 mg once daily, which can be increased to 30 mg and then 60 mg at 24-hour intervals 5
• Monitor for overly rapid correction of sodium levels 5
• Adverse effects include thirst (21%), dry mouth (7%), and polyuria (11%) 5
• Contraindicated with strong CYP3A inhibitors 5
• Risk of gastrointestinal bleeding in patients with cirrhosis (10% vs 2% with placebo) 5

Monitoring and Prevention of Complications

• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1, 5

Common Pitfalls to Avoid

• Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 5
• Inadequate monitoring during active correction 1
• Using fluid restriction in CSW, which can worsen outcomes 2, 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1

Recent Evidence and Recommendations

• The rapid intermittent administration of hypertonic saline is preferred for treatment of symptomatic hyponatremia 6
• For asymptomatic mild hyponatremia, adequate solute intake with an initial fluid restriction of 500 ml/day adjusted according to serum sodium levels is preferred 6
• Almost half of SIADH patients do not respond to fluid restriction as first-line therapy 6
• Urea and tolvaptan are considered the most effective second-line therapies in SIADH 6
• Gradual correction and clinical evaluation is preferable over rapid normalization of serum sodium 6, 7