Management of Hyponatremia
The management of hyponatremia should be based on symptom severity, volume status, and the underlying cause, with careful attention to correction rates to prevent osmotic demyelination syndrome. 1
Initial Assessment
- Hyponatremia should be further investigated and treated when serum sodium is less than 131 mmol/L 2
- Evaluation should include:
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
- Monitor serum sodium every 2 hours during initial correction 1
- Do not exceed total correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 2, 1
Mild to Moderate Symptomatic Hyponatremia
- For hypovolemic hyponatremia: discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1, 3
- For euvolemic hyponatremia (SIADH): implement fluid restriction to 1 L/day and consider oral sodium chloride supplementation 1
- For hypervolemic hyponatremia (cirrhosis, heart failure): fluid restriction to 1000-1500 mL/day and address underlying cause 1
Treatment Based on Volume Status
Hypovolemic Hyponatremia
- Discontinue diuretics 1
- Administer isotonic saline for volume repletion 1, 3
- Monitor serum sodium levels regularly 1
Euvolemic Hyponatremia (SIADH)
Hypervolemic Hyponatremia
- Fluid restriction to 1000-1500 mL/day for sodium <125 mmol/L 1
- For cirrhosis: consider albumin infusion 1
- Avoid hypertonic saline unless life-threatening symptoms are present 1
Special Considerations for Neurosurgical Patients
- Cerebral salt wasting (CSW) should be treated with replacement of serum sodium and intravenous fluids, not fluid restriction 2, 1
- Fludrocortisone may be considered for hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm 2
- Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients 2
- Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 2, 1
Correction Rate Guidelines
- Do not exceed correction of 8 mmol/L in 24 hours for most patients 2, 1
- For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy: use more cautious correction (4-6 mmol/L per day) 1
- Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
Monitoring and Safety Considerations
- Monitor serum sodium levels frequently during correction 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
- Inadequate monitoring during active correction 1
- Using fluid restriction in cerebral salt wasting 2, 1
- Failing to recognize and treat the underlying cause 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
- Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant 1, 5
Clinical Significance
- Hyponatremia is the most common electrolyte disorder encountered in clinical medicine 2
- Even mild hyponatremia is associated with cognitive impairment, gait disturbances, and increased rates of falls and fractures 4
- Hyponatremia increases risk for complications in patients with cirrhosis, including hepatic encephalopathy, hepatorenal syndrome, and spontaneous bacterial peritonitis 1