How to manage hyponatremia?

Management of Hyponatremia

The management of hyponatremia should be based on volume status assessment (hypovolemic, euvolemic, or hypervolemic) and symptom severity, with careful correction rates not exceeding 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome. 1

Assessment and Classification

Severity Assessment

• Mild: 130-135 mmol/L
• Moderate: 125-129 mmol/L
• Severe: <125 mmol/L 1

Volume Status Evaluation

1. Hypovolemic: Signs of dehydration, orthostatic hypotension, dry mucous membranes
2. Euvolemic: No signs of volume depletion or overload
3. Hypervolemic: Edema, ascites, signs of fluid overload 1, 2

Laboratory Workup

• Serum electrolytes, BUN/creatinine ratio
• Urinary sodium and potassium
• Serum and urine osmolality
• Consider thyroid and adrenal function tests 1

Treatment Algorithm

1. Severe Symptomatic Hyponatremia (Seizures, Coma, Respiratory Distress)

• Emergency treatment with 3% hypertonic saline:
  • Goal: Increase serum sodium by 4-6 mEq/L in first 1-2 hours
  • Do not exceed 8 mEq/L in 24 hours 1, 2
  • Calculate infusion rate (ml/kg/hr) = body weight (kg) × desired rate of increase 3
  • Monitor sodium levels frequently during correction

2. Hypovolemic Hyponatremia

• Normal saline infusion to restore both volume and sodium levels 1
• Treat underlying cause (e.g., gastrointestinal losses, diuretic use)
• Monitor correction rate closely

3. Euvolemic Hyponatremia

• Fluid restriction as primary management approach 1
• For SIADH:
  • Tolvaptan starting at 15 mg once daily (if appropriate) 1
  • Urea may be considered as an alternative 1
  • Demeclocycline for persistent cases 4

4. Hypervolemic Hyponatremia

• Fluid restriction and treatment of underlying condition (heart failure, cirrhosis) 1
• Loop diuretics to manage edematous states 1, 4
• Spironolactone (starting at 100 mg, up to 400 mg) for heart failure or cirrhosis 1

Critical Considerations

Correction Rate

• Target correction rate: 4-6 mEq/L per day
• Maximum correction: 8 mEq/L in 24 hours 1
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1

Medication Precautions

• Tolvaptan:

  • Contraindicated with strong CYP3A inhibitors 5
  • Avoid in patients with liver disease due to risk of gastrointestinal bleeding (10% vs 2% placebo) 5
  • Monitor for hypernatremia (occurred in 1.7% of patients in clinical trials) 5
  • Increased mortality in heart failure patients with hyponatremia (42% vs 38% placebo) 5

• Sodium chloride:

  • Excessive administration may lead to fluid overload in susceptible patients 6

High-Risk Factors for Osmotic Demyelination Syndrome (ODS)

• Advanced liver disease
• Alcoholism
• Severe hyponatremia
• Malnutrition
• Prior encephalopathy 1

Special Populations

Elderly Patients

• More susceptible to hyponatremia and its symptoms
• Chronic mild hyponatremia associated with cognitive impairment, gait disturbances, and increased falls/fractures 1, 2
• Careful monitoring during correction is essential

Monitoring

• Check serum sodium frequently during correction
• Adjust therapy to maintain target correction rate
• Monitor for neurological symptoms that could indicate ODS
• In patients treated with tolvaptan, monitor for hypernatremia and ensure serum sodium remains within normal limits 1, 5

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