Treatment of Hyponatremia
The treatment of hyponatremia should be based on symptom severity, volume status, and the 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:
Initial workup should include serum and urine osmolarity, urine electrolytes, uric acid, and assessment of extracellular fluid volume status 1
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (seizures, coma)
- Administer 3% hypertonic saline with a 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, 3
- Monitor serum sodium every 2 hours during initial correction 1
- Consider ICU admission for close monitoring 1
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 1-1.5 L/day for sodium <125 mmol/L 1
Treatment Based on Volume Status
Hypovolemic Hyponatremia
- Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1
- For severe dehydration with neurological symptoms, consider hypertonic saline with careful monitoring 1
Euvolemic Hyponatremia (SIADH)
- Fluid restriction to 1 L/day as first-line treatment 1, 3
- If no response to fluid restriction, consider:
Hypervolemic Hyponatremia
- Fluid restriction to 1-1.5 L/day for serum 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 for most patients 1, 3
- For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy: more cautious correction (4-6 mmol/L per day) 1, 3
- If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1
Special Considerations
Neurosurgical Patients
- Distinguish between SIADH and cerebral salt wasting (CSW) as treatment approaches differ significantly 1
- For CSW: Treatment focuses on volume and sodium replacement, not fluid restriction 1
- Consider fludrocortisone for hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm 1
- Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1
Pharmacological Options
- Vasopressin receptor antagonists (tolvaptan, conivaptan) can increase serum sodium levels significantly in euvolemic or hypervolemic hyponatremia 5, 2
- FDA clinical trials showed tolvaptan increased serum sodium by 4.0 mEq/L vs. 0.4 mEq/L with placebo over 4 days 5
- Urea is considered an effective and safe treatment option, particularly for SIADH 4
Common Pitfalls to Avoid
- Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 3
- Inadequate monitoring during active correction 1
- Using fluid restriction in cerebral salt wasting 1
- Failing to recognize and treat the underlying cause 1, 3
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
Monitoring and Follow-up
- For severe symptoms: Monitor serum sodium every 2 hours during initial correction 1
- For mild symptoms: Monitor sodium levels every 4 hours initially, then daily 3
- Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1