How is hyponatremia treated?

Treatment of Hyponatremia

The treatment of hyponatremia should be tailored to the patient's volume status (hypovolemic, euvolemic, or hypervolemic) and symptom severity, with correction rates not exceeding 8 mmol/L per 24 hours to prevent osmotic demyelination syndrome. 1

Classification and Initial Assessment

Treatment approach depends on:

1. Volume status assessment:

   • Hypovolemic: Urine sodium <20 mEq/L, signs of volume depletion
   • Euvolemic: Urine osmolality >500 mOsm/kg, urine sodium >20-40 mEq/L (SIADH)
   • Hypervolemic: Elevated urine osmolality, urine sodium <20 mEq/L, edema (heart failure, cirrhosis) 1

2. Symptom severity:

   • Severe: Seizures, altered mental status, coma
   • Moderate: Nausea, vomiting, headache
   • Mild/Asymptomatic: No significant symptoms 2

3. Sodium level:

   • Mild: 130-134 mmol/L
   • Moderate: 125-129 mmol/L
   • Severe: <125 mmol/L 3

Treatment Algorithm by Volume Status

1. Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• First-line: Free water restriction (1-1.5 L/day) 1
• Discontinue all hypotonic fluid administration 1
• Avoid hypertonic saline in most cases as it can worsen edema and ascites 1
• Consider vasopressin antagonists (vaptans) for short-term use (≤30 days) in severe or symptomatic cases
  • Start tolvaptan at 15 mg once daily, can titrate to 30 mg then 60 mg as needed 1
  • Tolvaptan has shown significant improvement in serum sodium levels (average increase of 5.7 mmol/L at Day 4 and 10.0 mmol/L at Day 30 in severe hyponatremia <125 mmol/L) 4
• Temporarily discontinue diuretics if serum sodium <125 mmol/L 1
• Optimize underlying condition treatment:
  • For heart failure: Appropriate heart failure medications 1
  • For cirrhosis: Manage ascites with diuretic therapy once hyponatremia is stabilized 1

2. Hypovolemic Hyponatremia

• First-line: Normal saline (0.9% NaCl) for volume repletion 3
• For severe symptoms: Consider 3% hypertonic saline 2

3. Euvolemic Hyponatremia (SIADH)

• First-line: Fluid restriction, salt tablets 3
• Second-line: Consider urea or tolvaptan 5
• For severe symptoms: 3% hypertonic saline 2

Management Based on Symptom Severity

Severe Symptoms (Seizures, Altered Mental Status, Coma)

• Administer 3% hypertonic saline to increase serum sodium by 4-6 mEq/L in first 1-2 hours 1
• Transfer to ICU for close monitoring 1
• Initial infusion rate (ml/kg per hour) can be estimated by: body weight (kg) × desired rate of increase in sodium (mmol/L per hour) 6

Moderate Symptoms (Nausea, Vomiting, Headache)

• Use isotonic saline (0.9% NaCl) for volume expansion 1
• Consider 3% hypertonic saline if symptoms worsen 1

Mild/No Symptoms

• Use isotonic saline for volume repletion if hypovolemic 1
• Fluid restriction for euvolemic or hypervolemic states 1, 3

Critical Monitoring Parameters

• Monitor serum sodium levels every 4-6 hours during active correction, then daily 1
• Do not exceed correction rate of 8 mmol/L per 24 hours to prevent osmotic demyelination syndrome 1
• For high-risk patients (alcoholism, malnutrition, liver disease), use lower correction rate of 4-6 mEq/L per day 1
• If correction occurs too rapidly, consider administering hypotonic fluids or desmopressin to re-lower sodium 1, 5

Cautions and Pitfalls

1. Avoid overly rapid correction of chronic hyponatremia, which can cause osmotic demyelination syndrome 2
2. Use vaptans cautiously as they can lead to overly rapid correction 1
3. Safety of vaptans is established only for 1 week to 1 month 1
4. Fluid restriction often fails in nearly half of SIADH patients 5
5. Monitor potassium, kidney function, and urine output regularly 1

Special Considerations for Specific Patient Groups

• Heart failure patients: Sodium restriction to around 2 L/day, consider ACEi or ARB therapy for long-term management 1
• Cirrhosis patients: Manage ascites with appropriate diuretic therapy once hyponatremia is stabilized 1
• Patients with chronic mild hyponatremia: Address increased risk of cognitive impairment, gait disturbances, falls, and fractures 2