How to manage hyponatremia (low sodium levels) in patients?

Management of Hyponatremia

For patients with hyponatremia, treatment should be guided by symptom severity, onset timing, and volume status, with correction rates not exceeding 8 mmol/L in 24 hours (4-6 mmol/L in high-risk patients) to prevent osmotic demyelination syndrome. 1

Classification and Initial Assessment

Hyponatremia is defined as serum sodium <135 mEq/L and classified by severity:

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

The approach to management requires assessment of:

1. Symptom severity (mild vs. severe)
2. Onset timing (acute <48 hours vs. chronic >48 hours)
3. Volume status (hypovolemic, euvolemic, or hypervolemic)

Emergency Management of Symptomatic Hyponatremia

Severely symptomatic hyponatremia (somnolence, seizures, coma, cardiorespiratory distress) is a medical emergency requiring immediate intervention:

• Administer 3% hypertonic saline to increase serum sodium by 4-6 mEq/L within 1-2 hours 2
• Monitor sodium levels every 4-6 hours during active correction 1
• Critical safety limit: Do not exceed correction of 10 mEq/L in first 24 hours 2

Management Based on Volume Status

1. Hypovolemic Hyponatremia

• First-line: Normal saline (0.9% NaCl) infusion 3
• Address underlying cause (GI losses, diuretic use, etc.)
• Monitor for overcorrection as volume repletion may lead to rapid water diuresis

2. Euvolemic Hyponatremia

• First-line: Fluid restriction to 1,000-1,500 mL/day for mild cases 1
• For SIADH:
  • Stricter fluid restriction (1,000 mL/day) for moderate cases 1
  • Consider tolvaptan for persistent cases (starting at 15 mg once daily, can increase to 30 mg after 24 hours, maximum 60 mg daily) 1, 4
  • Urea can be an alternative treatment option 2

3. Hypervolemic Hyponatremia

• First-line: Fluid restriction and treatment of underlying condition (heart failure, cirrhosis) 1
• Consider tolvaptan for persistent cases, especially in heart failure 1, 4
• Midodrine (7.5 mg three times daily) can be considered when vaptans are unavailable 1
• Avoid hypertonic saline in cirrhosis patients unless life-threatening symptoms are present 1

Correction Rate Guidelines

• Standard maximum correction rate: 8 mmol/L in 24 hours 1
• High-risk patients (alcoholism, liver disease, malnutrition): Limit to 4-6 mmol/L in 24 hours 1
• If overcorrection occurs, consider desmopressin to halt water diuresis 1

Monitoring Recommendations

• Check serum sodium every 4-6 hours during active correction 1
• For tolvaptan initiation, hospitalization is required with close monitoring 1, 4
• Monitor for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction) which typically presents 2-7 days after rapid correction 1

Outpatient Management

• Appropriate for asymptomatic mild hyponatremia (126-135 mEq/L) 1
• Fluid restriction and monitoring of sodium levels
• Hospitalization required for:
  • Severe symptoms
  • Sodium <120 mEq/L
  • Patients initiating tolvaptan 1

Special Considerations

• Tolvaptan may increase digoxin levels by 30% and lovastatin exposure by 1.4 times 4
• Tolvaptan is a weak inhibitor of CYP3A and an inhibitor of P-gp and BCRP 4
• Even mild chronic hyponatremia is associated with cognitive impairment, gait disturbances, and increased risk of falls and fractures 2
• Avoid fluid restriction in the first 24 hours of active treatment to prevent overly rapid correction 4