How is hyponatremia treated?

Treatment of Hyponatremia

The treatment of hyponatremia should be tailored to the underlying volume status, severity of symptoms, and chronicity of the condition, with careful attention to correction rates to prevent osmotic demyelination syndrome. 1

Classification and Diagnosis

Hyponatremia is defined as serum sodium concentration below 135 mmol/L, with treatment generally considered when levels fall below 130 mmol/L. Proper management requires determining:

1. Volume status: Hypovolemic, euvolemic, or hypervolemic
2. Severity: Mild (130-134 mmol/L), moderate (125-129 mmol/L), severe (<125 mmol/L)
3. Chronicity: Acute (<48 hours) vs chronic (>48 hours)
4. Symptoms: Mild (nausea, headache, weakness) vs severe (seizures, coma, altered mental status)

Laboratory Assessment

Volume Status	Urine Osmolality	Urine Sodium	Suggested Diagnosis
Hypovolemic	Variable	<20 mEq/L	Volume depletion
Euvolemic	>500 mOsm/kg	>20-40 mEq/L	SIADH
Hypervolemic	Elevated	<20 mEq/L	Heart failure, cirrhosis

Treatment Algorithm

1. Severe Symptomatic Hyponatremia (Emergency)

• Presentation: Seizures, coma, severe neurological symptoms
• Treatment:
  • Administer 3% hypertonic saline as 100-150 mL bolus or continuous infusion 1, 2
  • Target correction: 4-6 mEq/L in first 6 hours or until symptoms improve 1
  • Maximum correction: 8 mEq/L in 24 hours, not exceeding 12 mEq/L in 24 hours 3, 1
  • Monitor serum sodium every 2-4 hours during active correction 1
  • If correction exceeds safe limits, consider desmopressin or hypotonic fluids to prevent ODS 1

2. Hypovolemic Hyponatremia

• Presentation: Clinical signs of dehydration, orthostatic hypotension
• Treatment:
  • Isotonic (0.9%) saline infusion for plasma volume expansion 1
  • Discontinue diuretics or other causative medications 1
  • Once volume status is corrected, reassess sodium levels and adjust therapy

3. Euvolemic Hyponatremia (often SIADH)

• Treatment:

  • Mild to moderate (asymptomatic):

    • Fluid restriction (1-1.5 L/day) 1
    • High solute intake (salt and protein) 2
    • Consider oral sodium chloride tablets if no response to fluid restriction 3

  • Refractory cases:

    • Tolvaptan (vasopressin receptor antagonist) starting at 15 mg once daily, can be titrated up to 60 mg daily 4
    • Tolvaptan showed significant improvement in serum sodium levels compared to placebo in clinical trials 4
    • Oral urea (30-60 g/day) can be considered as an alternative 2

4. Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Treatment:
  • Fluid restriction to 1,000 mL/day for moderate hyponatremia (120-125 mEq/L) 3
  • More severe fluid restriction with albumin infusion for severe hyponatremia (<120 mEq/L) 3
  • Treat underlying condition (heart failure, cirrhosis)
  • Loop diuretics may be needed for volume management 1
  • Consider tolvaptan for short-term use in refractory cases 1, 4

Critical Considerations

Correction Rates

• Chronic hyponatremia: Maximum 8 mEq/L in 24 hours 3, 1
• Acute hyponatremia (<48 hours): Can be corrected more rapidly at 1 mEq/L/hour 3
• High-risk patients (alcoholism, malnutrition, liver disease): Lower correction rate of 4-6 mEq/L per day 3

Osmotic Demyelination Syndrome (ODS)

• Risk factors: Chronic hyponatremia, alcoholism, liver disease, malnutrition, hypokalemia 3
• Symptoms: Dysarthria, dysphagia, altered mental status, quadriparesis 3
• Prevention: Avoid correction exceeding 8 mEq/L in 24 hours 3, 1
• Management of overcorrection: Administration of hypotonic fluids or desmopressin 1, 2

Special Populations

• Cirrhosis patients: Hyponatremia reflects worsening hemodynamic status and increases risk of complications 3
• Neurosurgical patients: At higher risk of complications from hyponatremia, with prevalence as high as 50% 3
• Subarachnoid hemorrhage: Consider fludrocortisone to prevent natriuresis 1

Medication Considerations

• Discontinue medications that may cause or worsen hyponatremia (SSRIs, carbamazepine, thiazide diuretics, NSAIDs) 1
• Tolvaptan: Effective for euvolemic and hypervolemic hyponatremia but should be used short-term 4
• Albumin: Consider for hypervolemic hyponatremia in cirrhosis 3
• Hypertonic saline: Reserved for symptomatic or severe hyponatremia 5

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