What is the treatment for hyponatremia?

Treatment for Hyponatremia

The treatment of hyponatremia should be based on the severity of symptoms, volume status, and underlying cause, with fluid restriction of 1-1.5 L/day for mild to moderate cases and 3% hypertonic saline for severe symptomatic cases. 1

Classification and Initial Assessment

Hyponatremia is categorized by severity:

• Mild: 126-135 mEq/L (often asymptomatic)
• Moderate: 120-125 mEq/L (nausea, headache, confusion)
• Severe: <120 mEq/L (risk of seizures, coma, respiratory arrest) 1

Volume status assessment is crucial for determining treatment:

Volume Status	Clinical Signs	Urine Sodium	Common Causes
Hypovolemic	Orthostatic hypotension, dry mucous membranes, tachycardia	<20 mEq/L	GI losses, diuretics, CSW
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

Treatment Algorithm

1. Severe Symptomatic Hyponatremia (<120 mEq/L with seizures, coma)

• Administer 3% hypertonic saline to increase serum sodium by 4-6 mEq/L within 1-2 hours 1
• After symptoms abate, slow correction rate to avoid osmotic demyelination syndrome
• Critical safety parameters:
  • Total correction should not exceed 8 mEq/L over 24 hours 1
  • If 6 mEq/L is corrected in first 6 hours, limit further correction to 2 mEq/L in following 18 hours 1
  • Avoid increasing serum sodium by >10 mmol/L/day 1
  • Monitor sodium levels every 2 hours initially, then every 4 hours 1

2. Mild to Moderate Hyponatremia

• Fluid restriction of 1-1.5 L/day is the mainstay of treatment 1
• For moderate hyponatremia (120-125 mEq/L), restrict water to 1,000 mL/day 1

3. Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Isotonic saline to restore volume status 2
• Treat underlying cause (e.g., diuretics, GI losses)

Euvolemic Hyponatremia (e.g., SIADH)

• Fluid restriction as first-line therapy 1, 3
• Tolvaptan (vasopressin receptor antagonist) for short-term treatment (≤30 days) 1, 4
  • Starting dose: 15 mg once daily 4
  • Monitor for overly rapid correction and hypernatremia 4
  • Avoid in patients with liver disease due to risk of liver injury
  • Contraindicated with strong CYP3A inhibitors 4
• Urea as an effective second-line therapy for SIADH 3

Hypervolemic Hyponatremia

• Fluid restriction and sodium restriction 1
• Diuretic management for cirrhotic patients with ascites:
  • Start with aldosterone antagonist (spironolactone 100 mg/day)
  • Increase stepwise to maximum 400 mg/day if needed
  • Consider combination of aldosterone antagonist plus furosemide for recurrent ascites 1
• For heart failure patients, optimize heart failure medications 1

Special Considerations

Tolvaptan Efficacy

Clinical trials demonstrated tolvaptan's effectiveness in increasing serum sodium levels:

• In patients with serum sodium <135 mEq/L: 4.0 mEq/L increase by day 4 vs 0.4 mEq/L with placebo 4
• In patients with serum sodium <125 mEq/L: 5.7 mEq/L increase by day 4 vs 1.0 mEq/L with placebo 4

Common Adverse Effects of Tolvaptan

• Thirst (14% vs 5% placebo)
• Dry mouth (13% vs 4% placebo)
• Increased urination (11% vs 3% placebo) 4

Cautions and Complications

• Osmotic demyelination syndrome risk with overly rapid correction of chronic hyponatremia 1, 4
• Gastrointestinal bleeding risk in cirrhotic patients (10% with tolvaptan vs 2% with placebo) 4
• Hypernatremia risk (1.7% with tolvaptan vs 0.8% with placebo) 4
• Untreated hyponatremia can lead to severe complications including seizures, coma, and death 1

Treatment of Specific Causes

• Hypothyroidism-induced hyponatremia: Primary treatment with thyroid hormone replacement therapy 1
• CSW: Aggressive volume resuscitation with isotonic or hypertonic saline; consider mineralocorticoids (fludrocortisone) 1

By following this structured approach based on symptom severity, volume status, and underlying cause, hyponatremia can be effectively managed while minimizing the risk of complications.