Guidelines for Correcting Hyponatremia
The correction of hyponatremia should follow a controlled rate of 4-6 mEq/L per 24 hours, not exceeding 8 mEq/L per 24-hour period, especially in high-risk patients with advanced liver disease, alcoholism, or malnutrition to prevent osmotic demyelination syndrome. 1, 2
Classification and Initial Assessment
Hyponatremia is classified based on severity:
- Mild: 126-135 mEq/L
- Moderate: 120-125 mEq/L
- Severe: <120 mEq/L 1
Additionally, hyponatremia should be categorized by volume status:
- Hypovolemic hyponatremia
- Euvolemic hyponatremia
- Hypervolemic hyponatremia 1
Treatment Guidelines by Severity
Mild Hyponatremia (126-135 mEq/L)
- No specific management required beyond monitoring and water restriction
- Continue to monitor serum sodium levels 2
Moderate Hyponatremia (120-125 mEq/L)
- Water restriction to 1,000 mL/day
- Cessation of diuretics
- Monitor serum sodium every 4-6 hours during active correction 2, 1
Severe Hyponatremia (<120 mEq/L)
- More aggressive water restriction (<1,000 mL/day)
- Albumin infusion (5% IV)
- For symptomatic patients (seizures, coma, altered mental status): 3% hypertonic saline IV
- Hospital admission for close monitoring 2, 1
Special Considerations for Symptomatic Hyponatremia
For patients with severe symptoms (seizures, coma, altered mental status):
- Administer 3% hypertonic saline IV
- Target an initial increase of 4-6 mEq/L in the first 24 hours
- Monitor serum sodium every 4-6 hours during correction 1, 3
- Hypertonic saline should be limited to severely symptomatic hyponatremia or patients awaiting liver transplantation 2
Prevention of Osmotic Demyelination Syndrome (ODS)
ODS is a serious complication of rapid sodium correction, characterized by:
- Dysarthria, mutism, dysphagia
- Lethargy, affective changes
- Spastic quadriparesis, seizures, coma 4
To prevent ODS:
- Limit correction to 4-6 mEq/L per 24 hours, not exceeding 8 mEq/L in high-risk patients 2, 1
- High-risk patients include those with:
- Advanced liver disease
- Alcoholism
- Malnutrition
- Severe hyponatremia (<115 mEq/L) 5
- If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 2
Pharmacological Management
Vasopressin Receptor Antagonists (Vaptans)
- May be considered for persistent hyponatremia despite fluid restriction
- Should be used with caution and only for short-term (≤30 days)
- Must be initiated in a hospital setting
- Starting dose for tolvaptan is 15 mg once daily, can be increased to 30 mg after 24 hours, maximum 60 mg daily 4, 2
- Contraindicated in hypovolemic hyponatremia 4
Specific Management Based on Etiology
Hypovolemic Hyponatremia
- Plasma volume expansion with normal saline (0.9% sodium chloride)
- Correction of the underlying cause 1
Hypervolemic Hyponatremia
- Fluid restriction (1,000-1,500 mL/day)
- Avoidance of excessive hypotonic fluids (5% dextrose)
- Consider salt supplementation with oral salt tablets if fluid restriction alone is insufficient 1
Hyponatremia in Cirrhosis
- Mild: monitoring and avoidance of excessive free water intake
- Moderate: fluid restriction to 1,000 mL/day, discontinuation of diuretics
- Severe: aggressive fluid restriction, albumin infusion 2, 1
Monitoring During Correction
- Serum sodium levels should be checked every 4-6 hours during active correction
- Monitor fluid status, neurological status, urine output, and specific gravity
- Be vigilant for signs of ODS, which typically presents 2-7 days after rapid correction 2, 1
Caution
Recent research indicates that ODS can occur even when following the guideline-recommended correction rates, particularly in patients with severe hyponatremia (<115 mEq/L). For these patients, consider limiting correction to <8 mEq/L per 24 hours 5.
While rapid correction increases ODS risk, it may reduce in-hospital mortality and length of stay 6. This highlights the importance of careful monitoring and individualized correction rates based on patient risk factors.