What is the approach to treating hyponatremia?

Approach to Treating Hyponatremia

The treatment of hyponatremia should be guided by volume status assessment, severity of symptoms, and rate of sodium correction to prevent complications like osmotic demyelination syndrome. 1

Initial Classification and Assessment

Hyponatremia should be classified based on:

1. Serum sodium levels 1:

   • Mild: 126-135 mEq/L
   • Moderate: 120-125 mEq/L
   • Severe: <120 mEq/L

2. Volume status 1:

   Volume Status	Clinical Signs	Urine Sodium	Likely Causes
   Hypovolemic	Orthostatic hypotension, dry mucous membranes, tachycardia	<20 mEq/L	GI losses, diuretics, CSW, adrenal insufficiency
   Euvolemic	No edema, normal vital signs	>20-40 mEq/L	SIADH, hypothyroidism, adrenal insufficiency
   Hypervolemic	Edema, ascites, elevated JVP	<20 mEq/L	Heart failure, cirrhosis, renal failure

3. Symptom severity:

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

Treatment Algorithm

1. Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with severe symptoms (somnolence, seizures, coma):

• Administer 3% hypertonic saline 1, 2, 3:
  • 100-150 mL IV bolus or continuous infusion
  • Goal: Increase serum sodium by 4-6 mEq/L within 1-2 hours
  • Do NOT exceed correction of 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome 1
  • Check sodium levels every 2 hours initially, then every 4 hours 1

2. Hypovolemic Hyponatremia

• Administer isotonic (0.9%) saline 1, 4
• Treat underlying cause (e.g., GI losses, diuretics)
• Monitor serum sodium to prevent overly rapid correction

3. Euvolemic Hyponatremia

For SIADH:

• First-line: Fluid restriction (500 mL/day initially) 3
• Second-line options (if fluid restriction fails):
  • Urea: Effective and safe treatment for SIADH 3
  • Tolvaptan (vasopressin receptor antagonist) 1, 5:
    • Starting dose: 15 mg once daily
    • Maximum duration: ≤30 days
    • Monitor for overly rapid correction
    • Contraindicated with strong CYP3A inhibitors 5
    • Avoid grapefruit juice during treatment 5

4. Hypervolemic Hyponatremia

• Treat underlying condition (heart failure, cirrhosis, renal failure) 4
• Fluid restriction (primary approach) 4
• Loop diuretics may be beneficial 6
• Tolvaptan can be considered for heart failure or cirrhosis 1, 5
• Albumin infusion for patients with hypoalbuminemia and cirrhosis 1

Correction Rate Guidelines

• Chronic hyponatremia: 4-6 mEq/L per 24 hours, not exceeding 8 mEq/L per 24 hours 1
• Risk factors for osmotic demyelination syndrome:
  • Overly rapid correction of chronic hyponatremia
  • Serum sodium <120 mEq/L
  • Alcoholism, malnutrition, liver disease

Monitoring and Complications

• Monitor serum sodium every 2-4 hours during initial treatment 1
• Watch for overcorrection: If sodium rises too quickly, consider administering hypotonic fluids or desmopressin 3
• Complications of untreated hyponatremia 1:
  • Seizures, coma, death (especially when sodium <120 mEq/L)
  • 25% mortality rate when sodium <120 mEq/L vs. 9.3% when >120 mEq/L
  • Even mild hyponatremia increases risk of falls, fractures, and cognitive impairment 2

Special Considerations

• Liver cirrhosis: Associated with poor prognosis, higher risk of refractory ascites, spontaneous bacterial peritonitis, and hepatorenal syndrome 1
• Diabetic patients: When serum glucose normalizes, adjust fluid therapy appropriately 1
• Medications: Review and adjust medications that may cause or worsen hyponatremia 6

Remember that the treatment approach should be tailored based on the underlying cause, severity of symptoms, and chronicity of hyponatremia, with careful monitoring to prevent complications from both the condition and its treatment.