How is hyponatremia treated?

Treatment of Hyponatremia

The treatment of hyponatremia should be based on the underlying cause, volume status assessment, and symptom severity, with fluid restriction for SIADH, isotonic saline for hypovolemic hyponatremia, and 3% hypertonic saline for severe symptomatic cases. 1

Initial Assessment and Classification

Proper treatment requires determining the type of hyponatremia based on volume status:

• Hypovolemic hyponatremia:

  • Clinical signs: Orthostatic hypotension, dry mucous membranes, tachycardia
  • Urine sodium: <20 mEq/L
  • Common causes: GI losses, diuretics, cerebral salt wasting (CSW)

• Euvolemic hyponatremia:

  • Clinical signs: No edema, normal vital signs
  • Urine sodium: >20-40 mEq/L
  • Common causes: SIADH, hypothyroidism, adrenal insufficiency

• Hypervolemic hyponatremia:

  • Clinical signs: Edema, ascites, elevated JVP
  • Urine sodium: <20 mEq/L
  • Common causes: Heart failure, cirrhosis, renal failure 1

Treatment Algorithm Based on Symptom Severity

1. Severe Symptomatic Hyponatremia (seizures, coma, altered mental status)

• Immediate intervention with 3% hypertonic saline:
  • Goal: Increase serum sodium by 4-6 mEq/L within 1-2 hours or until severe symptoms improve 1, 2
  • Do not exceed correction of 8 mEq/L in 24 hours to avoid osmotic demyelination syndrome 2
  • For neurosurgical patients, consider ICU monitoring with q2hr sodium checks 2

2. Moderate Symptomatic Hyponatremia (nausea, headache, confusion)

• For serum sodium 120-125 mEq/L:
  • Fluid restriction to 1,000 mL/day 1
  • Consider 3% hypertonic saline if symptoms worsen
  • Monitor serum sodium every 4-6 hours 2

3. Mild or Asymptomatic Hyponatremia (126-135 mEq/L)

• For serum sodium >130 mEq/L:
  • May not require active intervention beyond monitoring 1
  • Address underlying cause

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics if applicable 1
• Provide isotonic saline (0.9% NaCl) for volume resuscitation 1, 3
• Correct underlying cause (GI losses, adrenal insufficiency)

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1,000 mL/day as first-line therapy 1, 2
• For non-responders to fluid restriction (almost 50% of cases), consider:
  • Urea (effective and safe second-line therapy) 1, 4
  • Tolvaptan (vasopressin receptor antagonist) for short-term use ≤30 days 1, 5
    • Starting dose: 15 mg once daily
    • Can increase to 30 mg, then 60 mg if needed
    • Avoid fluid restriction during first 24 hours of tolvaptan therapy 5
  • Salt tablets (NaCl 100 mEq PO TID) 2
  • High protein diet 2

Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

• Fluid restriction to 1,000 mL/day 1
• Reduce or temporarily discontinue diuretics 1
• For cirrhosis-related hyponatremia:
  • Consider albumin infusion 1
  • Tolvaptan may be considered for short-term use (≤30 days) 1, 5

Special Consideration: Cerebral Salt Wasting (CSW)

• Aggressive volume resuscitation with isotonic or hypertonic saline 1
• Consider fludrocortisone (mineralocorticoid) to correct negative sodium balance 2, 1
• Avoid fluid restriction 2

Critical Safety Considerations

1. Avoid overly rapid correction:

   • Do not exceed 8 mEq/L in 24 hours 2
   • Risk of osmotic demyelination syndrome with correction >10 mEq/L in 24 hours 6, 7

2. Monitor serum sodium frequently:

   • Every 2-4 hours in severe cases
   • Daily in mild cases

3. Adjust therapy based on response:

   • If correction is too rapid, consider administering desmopressin or hypotonic fluids 4
   • If correction is too slow, intensify therapy

4. For cirrhotic patients:

   • Even modest hyponatremia (131-135 mEq/L) increases risk of complications including hepatic encephalopathy (OR 3.4), hepatorenal syndrome (OR 3.5), and spontaneous bacterial peritonitis (OR 2.4) 2, 1

Pharmacological Options

1. 3% Hypertonic Saline:

   • Reserved for severe symptomatic hyponatremia 3
   • Can be administered as 100-150 mL boluses or continuous infusion 4

2. Tolvaptan:

   • Effective for euvolemic or hypervolemic hyponatremia 5
   • Contraindicated in hypovolemic hyponatremia
   • Limited to 30 days due to risk of liver injury 1, 5
   • Shown to increase serum sodium by 4.0 mEq/L vs 0.4 mEq/L with placebo by day 4 5

3. Urea:

   • Effective and safe second-line therapy for SIADH 1, 4
   • Better tolerated than vaptans by many patients