What are the treatment options for hyponatremia?

Treatment of Hyponatremia

The treatment of hyponatremia should be based on volume status assessment, severity of symptoms, and rate of onset, with fluid restriction to 1,000 mL/day as first-line therapy for moderate hyponatremia (120-125 mEq/L) and more severe fluid restriction with albumin infusion for severe hyponatremia (<120 mEq/L). 1

Classification and Assessment

Hyponatremia is defined as serum sodium <135 mEq/L and is the most common electrolyte disorder, affecting approximately 5% of adults and 35% of hospitalized patients 2. Proper management requires:

1. Classification by severity:

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

2. Classification by volume status:

   • Hypovolemic: Volume depletion (urine Na <20 mEq/L)
   • Euvolemic: SIADH (urine osmolality >500 mOsm/kg, urine Na >20-40 mEq/L)
   • Hypervolemic: Heart failure, cirrhosis (elevated urine osmolality, urine Na <20 mEq/L) 3

3. Symptom assessment:

   • Mild symptoms: Nausea, muscle cramps, gait instability, lethargy, headache, dizziness
   • Severe symptoms: Confusion, seizures, coma 1, 2

Treatment Algorithm

1. Symptomatic Severe Hyponatremia (Medical Emergency)

For patients with severe symptoms (seizures, coma, cardiorespiratory distress):

• Administer 3% hypertonic saline to increase serum sodium by 4-6 mEq/L in the first 1-2 hours 2
• Target correction rate: 4-8 mEq/L per day, with maximum safe limit of 10-12 mEq/L in any 24-hour period 3
• For high-risk patients (malnourished, alcoholic, liver disease), limit correction to 4-6 mEq/L per day 3
• Monitor serum sodium every 2-4 hours initially 3

2. Hypovolemic Hyponatremia

• Treat with isotonic saline (0.9% NaCl) 3
• Discontinue diuretics and/or laxatives 1
• Address underlying cause (e.g., dehydration, renal losses) 4

3. Euvolemic Hyponatremia (e.g., SIADH)

• Mild (126-135 mEq/L): Monitor and restrict fluid intake 1
• Moderate (120-125 mEq/L): Fluid restriction to 1,000 mL/day 1
• Severe (<120 mEq/L): More severe fluid restriction with albumin infusion 1
• For persistent cases: Consider vasopressin receptor antagonists (vaptans) for short-term use (≤30 days) 3, 5
  • Tolvaptan starting dose: 15 mg once daily 5
  • Tolvaptan has been shown to significantly increase serum sodium levels in patients with euvolemic or hypervolemic hyponatremia 5

4. Hypervolemic Hyponatremia (e.g., Heart Failure, Cirrhosis)

• Mild (126-135 mEq/L) with normal creatinine: Continue diuretic therapy with close monitoring 3
• Moderate (120-125 mEq/L) with normal creatinine: Consider stopping diuretics 3
• Moderate (120-125 mEq/L) with elevated creatinine: Stop diuretics and give volume expansion 3
• Severe (<120 mEq/L): Stop diuretics and consider volume expansion with colloid or saline 3
• Dietary salt restriction (90 mmol salt/day) 3
• Consider albumin infusion for severe cases 1

Monitoring and Prevention of Complications

• Check serum sodium every 2-4 hours initially, then every 4-6 hours during active correction 3
• Critical safety parameter: Do not exceed correction rate of 8 mEq/L in 24 hours (4-6 mEq/L for high-risk patients) to prevent osmotic demyelination syndrome (ODS) 1, 3
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 3
• For patients with liver disease, be particularly cautious as they are at increased risk for ODS 1

Special Considerations

• Cirrhosis: Hyponatremia reflects worsening hemodynamic status and is associated with increased risk of hepatic encephalopathy, hepatorenal syndrome, and spontaneous bacterial peritonitis 1
• Neurosurgical patients: Evaluate for cerebral salt wasting vs. SIADH, as treatment approaches differ 1
• Chronic hyponatremia: Even mild chronic hyponatremia is associated with cognitive impairment, gait disturbances, and increased rates of falls and fractures 2

Pharmacological Options

• Vaptans (vasopressin receptor antagonists): Effective for SIADH and hypervolemic hyponatremia, but monitor for overly rapid correction and increased thirst 2, 6
• Urea: Effective second-line therapy for SIADH but has poor palatability and may cause gastric intolerance 2, 6
• Loop diuretics: Can be used once hyponatremia is stabilized 3

By following this structured approach to hyponatremia management based on volume status, symptom severity, and careful monitoring of correction rates, clinicians can effectively treat this common electrolyte disorder while minimizing the risk of complications.