What is the treatment approach for hyponatremia?

Treatment Approach for Hyponatremia

The treatment of hyponatremia should be guided by severity, chronicity, and volume status, with correction rates not exceeding 8 mmol/L in 24 hours (4-6 mmol/L for high-risk patients) to avoid osmotic demyelination syndrome. 1

Classification and Initial Assessment

Hyponatremia is classified by:

• Severity:

  • Mild: 126-135 mEq/L
  • Moderate: 120-125 mEq/L
  • Severe: <120 mEq/L 1

• Chronicity:

  • Acute: developed within 48 hours
  • Chronic: developed over >48 hours 1

• Volume status:

  • Hypovolemic
  • Euvolemic
  • Hypervolemic 1, 2

Treatment Algorithm Based on Severity and Symptoms

1. Severe Symptomatic Hyponatremia (<120 mEq/L with severe symptoms)

• First-line: 3% hypertonic saline as 100-150 mL bolus or continuous infusion 1, 3
  • Goal: Increase serum sodium by 4-6 mEq/L within 1-2 hours to relieve severe symptoms 2
  • Monitor sodium levels every 4-6 hours during active correction 1
  • CAUTION: Do not exceed correction rate of 8 mmol/L in 24 hours (4-6 mmol/L in high-risk patients) 1

2. Moderate Hyponatremia (120-125 mEq/L)

• Strict fluid restriction to 1,000 mL/day 1
• Consider albumin infusion 1
• For hypervolemic or euvolemic hyponatremia:
  • Consider tolvaptan starting at 15 mg once daily (can increase to 30 mg after 24 hours, maximum 60 mg daily) 1, 4
  • Alternative: Midodrine 7.5 mg three times daily when vaptans unavailable 1

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

• Fluid restriction to 1,000-1,500 mL/day 1
• Adequate solute intake (salt and protein) 3
• Outpatient management appropriate for asymptomatic cases 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Normal saline infusions to restore volume 5
• Address underlying cause (e.g., gastrointestinal losses, burns) 6

Euvolemic Hyponatremia (including SIADH)

• First-line: Fluid restriction (initial 500 mL/day, adjusted based on sodium levels) 3
• Second-line (if no response to fluid restriction):
  • Oral urea (effective and safe) 3
  • Tolvaptan (shown effective in clinical trials) 4, 3
  • Consider salt tablets 5

Hypervolemic Hyponatremia

• Treat underlying cause (heart failure, cirrhosis, renal disease) 5
• Strict fluid restriction 5
• Loop diuretics may be useful 6
• Consider tolvaptan for heart failure patients 4, 2

Important Considerations and Pitfalls

• Avoid overly rapid correction: Risk of osmotic demyelination syndrome, especially in alcoholism, malnutrition, or liver disease 1, 2

  • Symptoms appear 2-7 days after rapid correction: dysarthria, dysphagia, oculomotor dysfunction 1
  • Diagnosed with brain MRI 1

• Monitoring requirements:

  • Check serum sodium every 4-6 hours during active correction 1
  • Consider desmopressin to halt water diuresis if overcorrection occurs 1, 3

• Special populations:

  • Patients with cirrhosis: Avoid hypertonic saline unless life-threatening symptoms present 1
  • Tolvaptan may increase risk of gastrointestinal bleeding in some patients 1

• Hospitalization criteria:

  • Severe symptoms
  • Sodium <120 mEq/L
  • Patients initiating tolvaptan 1

• Clinical impact: Even mild chronic hyponatremia is associated with cognitive impairment, gait disturbances, increased falls and fractures 2

By following this structured approach based on severity, chronicity, and volume status, clinicians can effectively manage hyponatremia while minimizing the risk of complications.