What is the treatment for critical hyponatremia?

Treatment of Critical Hyponatremia

For critical hyponatremia with severe symptoms (somnolence, obtundation, coma, seizures, or cardiorespiratory distress), administer 3% hypertonic saline boluses to raise sodium by 4-6 mEq/L in the first 1-2 hours, not exceeding 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Management

Severity Classification

• Mild: 130-135 mmol/L
• Moderate: 125-129 mmol/L
• Severe: <125 mmol/L 1

Symptom Evaluation

• Mild symptoms: Nausea, vomiting, weakness, headache, mild neurocognitive deficits 2
• Severe symptoms: Delirium, confusion, impaired consciousness, ataxia, seizures, brain herniation 1, 2

Treatment Algorithm Based on Volume Status

1. Hypovolemic Hyponatremia

• Primary treatment: Normal saline infusion 1
• Monitoring: Check serum sodium every 4-6 hours initially 1
• Target: Correction rate of 4-6 mEq/L per day, not exceeding 8 mEq/L in 24 hours 1

2. Euvolemic Hyponatremia

• For SIADH: Consider tolvaptan starting at 15 mg once daily (must be initiated in hospital setting) 1, 3
  • Caution: Tolvaptan use should not exceed 30 days due to risk of liver injury 1, 3
  • Monitoring: Close monitoring of serum sodium to prevent overcorrection 3
• Alternative: Urea (30 g/day dissolved in water or flavored beverage) 1
  • Advantage: Lower risk of liver injury compared to vaptans and doesn't increase ascites or edema 1

3. Hypervolemic Hyponatremia

• Primary approach: Fluid restriction and treatment of underlying condition 1
• For heart failure: Consider spironolactone (starting at 100 mg, up to 400 mg) 1

Management of Severe Symptomatic Hyponatremia

Immediate Intervention

• 3% hypertonic saline boluses to raise sodium by 4-6 mEq/L in first 1-2 hours 1, 4
• Continuous monitoring of serum sodium levels every 4-6 hours 1
• Prevention of overcorrection: Consider desmopressin when correction rates exceed 8 mEq/L in 24 hours 1

Important Precautions

• Avoid overly rapid correction: Limit to 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome (ODS) 1, 5
• Risk factors for ODS: Advanced liver disease, alcoholism, severe hyponatremia, malnutrition, metabolic derangements, low cholesterol, prior encephalopathy 1
• If overcorrection occurs: Relower serum sodium to keep daily increase below 10 mmol/L/24 hours 6

Special Considerations

Medication Interactions

• Tolvaptan interactions:
  • Contraindicated with strong CYP3A inhibitors 3
  • Avoid moderate CYP3A inhibitors and grapefruit juice 3
  • Monitor potassium when used with angiotensin receptor blockers, ACE inhibitors, or potassium-sparing diuretics 3

Symptomatic Management

• Consider antiemetics (ondansetron 4-8mg or metoclopramide 10mg) 30 minutes before sodium administration to reduce nausea 1

Follow-up and Monitoring

• Frequent measurements of serum sodium during correction phase are mandatory 6
• Target correction rate: 4-6 mEq/L per day, not exceeding 8 mEq/L in 24 hours 1
• Continue monitoring even after normalization of serum sodium to ensure levels remain within normal limits 3

Remember that treatment of critical hyponatremia requires balancing the risks of cerebral edema from untreated severe hyponatremia against the risk of osmotic demyelination from overly rapid correction.