Treatment of Hyponatremia
The treatment of hyponatremia should be based on the severity of symptoms, volume status, and underlying cause, with careful attention to correction rates to prevent osmotic demyelination syndrome. 1
Initial Assessment and Classification
- Evaluate volume status to determine if hyponatremia is hypovolemic, euvolemic, or hypervolemic 1
- Check serum and urine osmolality, urine electrolytes, and uric acid to determine the underlying cause 1
- Classify severity: mild (130-134 mmol/L), moderate (125-129 mmol/L), or severe (<125 mmol/L) 2
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (seizures, coma)
- Administer 3% hypertonic saline with goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1
- Do not exceed total correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 3
- Consider ICU admission for close monitoring during treatment 1
Mild to Moderate Symptomatic or Asymptomatic Hyponatremia
- Treat according to volume status and underlying cause 1
- Correction rate should not exceed 8 mmol/L in 24 hours 3, 1
- Patients with advanced liver disease, alcoholism, or malnutrition require even more cautious correction (4-6 mmol/L per day) 1
Treatment Based on Volume Status
Hypovolemic Hyponatremia
- Discontinue diuretics if applicable 1
- Administer isotonic saline (0.9% NaCl) for volume repletion 1
- Monitor serum sodium levels to ensure appropriate correction rate 1
Euvolemic Hyponatremia (SIADH)
Hypervolemic Hyponatremia (cirrhosis, heart failure)
- Fluid restriction to 1000-1500 mL/day for moderate hyponatremia 1
- More severe fluid restriction plus albumin infusion for severe hyponatremia 1
- Avoid hypertonic saline unless life-threatening symptoms are present 1
Special Considerations for Neurosurgical Patients
- Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches differ significantly 3, 1
- For CSW, treat with replacement of sodium and intravenous fluids 3
- Fludrocortisone may be considered in subarachnoid hemorrhage patients at risk of vasospasm 3
- Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients 3
- Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 3, 1
Monitoring During Treatment
- For severe symptoms: monitor serum sodium every 2 hours during initial correction 1
- 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
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 (can worsen outcomes) 1
- Failing to recognize and treat the underlying cause 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
- Ignoring mild hyponatremia as clinically insignificant 1, 4