What are the treatment guidelines for hyponatremia?

Hyponatremia Treatment Guidelines

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

Initial Assessment and Classification

• Hyponatremia is defined as serum sodium <135 mmol/L and should be classified by severity: mild (126-135 mmol/L), moderate (120-125 mmol/L), and severe (<120 mmol/L) 1
• Initial workup should include serum and urine osmolality, urine electrolytes, uric acid, and assessment of extracellular fluid volume status to determine the underlying cause 1
• Categorize patients according to volume status: hypovolemic, euvolemic, or hypervolemic hyponatremia 2

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, 3
• Total correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 4
• Consider ICU admission for close monitoring during treatment 1
• Monitor serum sodium every 2 hours during initial correction 1
• Bolus infusion of hypertonic saline (100 mL of 3% saline) produces faster initial elevation of sodium than continuous infusion with quicker restoration of consciousness 5

Mild to Moderate Symptomatic or Asymptomatic Hyponatremia

• For euvolemic hyponatremia (SIADH): fluid restriction to 1 L/day is the cornerstone of treatment 1, 3
• For hypovolemic hyponatremia: discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1
• For hypervolemic hyponatremia (cirrhosis, heart failure): fluid restriction to 1000-1500 mL/day for moderate to severe hyponatremia (Na <125 mmol/L) 1
• Consider adding oral sodium chloride 100 mEq three times daily if no response to fluid restriction in SIADH 4

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics and administer isotonic saline for volume repletion 1
• A urinary sodium <30 mmol/L has a positive predictive value of 71-100% for response to 0.9% saline infusion 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day as first-line treatment 1, 3
• If no response to fluid restriction, consider:
  • Oral sodium chloride 100 mEq three times daily 4
  • Urea (considered effective and safe) 1, 6
  • Vasopressin receptor antagonists (tolvaptan) for resistant cases 7

Hypervolemic Hyponatremia

• Fluid restriction to 1000-1500 mL/day for sodium <125 mmol/L 1
• Consider albumin infusion for patients with cirrhosis 1
• Avoid hypertonic saline unless life-threatening symptoms are present 1

Correction Rate Guidelines

• Maximum increase of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 3, 4
• For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy: more cautious correction (4-6 mmol/L per day) 1
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 6

Pharmacological Interventions

Vasopressin Receptor Antagonists (Vaptans)

• Tolvaptan is FDA-approved for clinically significant hypervolemic and euvolemic hyponatremia (serum sodium <125 mEq/L or less marked hyponatremia that is symptomatic and has resisted correction with fluid restriction) 7
• Must be initiated in a hospital setting where serum sodium can be closely monitored 7
• Starting dose is 15 mg once daily, which can be increased to 30 mg after 24 hours, and to a maximum of 60 mg daily 7
• Should not be administered for more than 30 days to minimize risk of liver injury 7
• Contraindicated in hypovolemic hyponatremia, patients unable to sense or respond to thirst, and those taking strong CYP3A inhibitors 7

Other Pharmacological Options

• Demeclocycline for SIADH (second-line treatment) 3
• Fludrocortisone for cerebral salt wasting, particularly in subarachnoid hemorrhage patients at risk of vasospasm 1
• Urea is considered an effective and safe treatment for SIADH 6

Special Considerations

Cerebral Salt Wasting vs. SIADH

• In neurosurgical patients, cerebral salt wasting (CSW) is more common than SIADH 1
• CSW requires volume and sodium replacement, not fluid restriction 1
• Fluid restriction should be avoided in subarachnoid hemorrhage patients at risk of vasospasm 1

Cirrhosis and Advanced Liver Disease

• Patients with cirrhosis require more cautious correction (4-6 mmol/L per day) 1
• Hyponatremia in cirrhosis reflects worsening hemodynamic status 1
• Serum Na ≤130 mEq/L increases risk for hepatic encephalopathy, hepatorenal syndrome, and spontaneous bacterial peritonitis 1

Common Pitfalls to Avoid

• Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 8
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1

Monitoring During Treatment

• For severe symptoms: monitor serum sodium every 2 hours during initial correction 1
• For mild symptoms or asymptomatic: monitor every 4-6 hours initially, then daily 4
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1