How is hyponatremia managed?

Management of Hyponatremia

The management of hyponatremia should be based on the patient's volume status, with correction rates not exceeding 8 mmol/L in 24 hours to avoid osmotic demyelination syndrome. 1

Initial Assessment and Classification

Hyponatremia management begins with determining the patient's volume status:

• Hypovolemic hyponatremia: Characterized by dehydration and orthostatic hypotension
• Euvolemic hyponatremia: No signs of dehydration or fluid overload
• Hypervolemic hyponatremia: Presents with edema, ascites, or fluid overload 1

Symptoms depend on severity and rate of development:

• Mild symptoms: Nausea, vomiting, weakness, headache
• Severe symptoms: Delirium, impaired consciousness, ataxia, seizures, coma 1, 2

Treatment Algorithm Based on Volume Status

1. Hypovolemic Hyponatremia

• First-line treatment: Isotonic (0.9%) saline infusion 1
• Goal: Volume expansion to restore euvolemia
• Monitor: Hemodynamic parameters (blood pressure, heart rate) and serum sodium levels

2. Euvolemic Hyponatremia

• First-line treatment: Fluid restriction (<1-1.5 L/day) 1
• Second-line options:
  • Urea: Effective but may have poor palatability and gastric intolerance 2
  • Tolvaptan: Consider for short-term use (≤30 days) in SIADH
    • Initial dose: 15 mg once daily
    • Maximum dose: 60 mg daily
    • Must be initiated in hospital setting with close monitoring 1, 3
    • Caution: Avoid in patients with liver disease due to risk of liver injury 3

3. Hypervolemic Hyponatremia

• First-line treatment: Fluid restriction + diuretics 1
• Management focus: Treat underlying condition (heart failure, cirrhosis, renal disease)

Management of Severe Symptomatic Hyponatremia

For patients with severe symptoms (seizures, coma, cardiorespiratory distress):

• Emergency treatment: 3% hypertonic saline bolus or infusion 1, 4
• Goal: Increase serum sodium by 4-6 mmol/L within 1-2 hours to reverse encephalopathy 2
• Critical safety limit: Do not exceed correction of 8-10 mmol/L in 24 hours 1
• Monitoring: Check serum sodium every 2-4 hours initially in symptomatic patients 1

Correction Rate Guidelines

• Standard correction rate: 4-6 mmol/L per day, not exceeding 8 mmol/L per 24-hour period 1
• High-risk patients: More conservative correction in patients with:
  • Severe malnutrition
  • Alcoholism
  • Advanced liver disease
  • Children (due to larger brain/skull size ratio) 1

Monitoring Recommendations

• Serum sodium: Every 2-4 hours initially in symptomatic patients; daily until stable, then weekly for 1 month 1
• Fluid input/output: Measure carefully to guide ongoing therapy 1
• Daily weight: To assess fluid status 1

Medication Considerations

• Avoid medications that may worsen hyponatremia, including certain antibiotics with high sodium content 1
• Tolvaptan drug interactions:
  • Contraindicated with strong CYP3A inhibitors
  • Avoid with moderate CYP3A inhibitors and grapefruit juice
  • Monitor when used with angiotensin receptor blockers, ACE inhibitors, and potassium-sparing diuretics due to 1-2% higher risk of hyperkalemia 3
  • Avoid concomitant use with V2-receptor agonists like desmopressin 3

Complications to Watch For

• Osmotic demyelination syndrome (ODS): Typically presents 2-7 days after rapid sodium correction with initial symptoms such as seizures or encephalopathy 1
• Overcorrection: If sodium correction exceeds recommended limits, consider administration of hypotonic fluids or desmopressin to prevent ODS 4
• Hypernatremia: Monitor for development during treatment 3

By following these guidelines and carefully monitoring sodium correction rates, clinicians can effectively manage hyponatremia while minimizing the risk of serious complications.