How to manage hyponatremia (low sodium levels)?

Management of Hyponatremia

Treatment of hyponatremia should be based on the underlying cause, volume status, severity of symptoms, and rate of development, with correction not exceeding 8-10 mmol/L in the first 24 hours to avoid osmotic demyelination syndrome. 1

Diagnosis and Classification

Hyponatremia is defined as serum sodium <135 mmol/L and should be further investigated and treated when levels fall below 131 mmol/L 2. Proper management requires determining:

1. Volume status:

   • Hypovolemic: Signs include orthostatic hypotension, tachycardia, dry mucous membranes, reduced skin turgor, and low central venous pressure (<5 cm H₂O) 1
   • Euvolemic: Normal volume status, often seen in SIADH
   • Hypervolemic: Edema, ascites, elevated CVP (>10 cm H₂O) 1

2. 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 (seizures, coma)

• Immediate action: Administer 3% hypertonic saline 1
• Target: Increase serum sodium by 6 mmol/L over 6 hours or until severe symptoms resolve 1
• Maximum correction: 8-10 mmol/L in first 24 hours 1
• Monitoring: Check serum sodium every 2-4 hours 1

2. Hypovolemic Hyponatremia

• First step: Discontinue diuretics if they are the cause 1
• Treatment: Administer isotonic saline (0.9% NaCl) to restore intravascular volume 1
• Monitoring: Follow serum sodium levels every 4-6 hours initially

3. Euvolemic Hyponatremia (SIADH)

• First-line: Fluid restriction of 1-1.5 L/day 1
• Pharmacologic options:
  • Vaptans (e.g., tolvaptan): Selectively inhibit V2 receptors of vasopressin, enhancing water excretion without affecting electrolyte excretion 2, 3
  • Other options: Urea, diuretics, lithium, or demeclocycline 2

4. Hypervolemic Hyponatremia (heart failure, cirrhosis)

• Primary approach: Treat underlying condition and restrict fluid intake to 1-1.5 L/day 2, 1
• Diuretic therapy: Spironolactone 100-400 mg/day with or without furosemide 40-160 mg/day for cirrhosis 1
• Consider: Vaptans for short-term use in appropriate patients 2, 1

Special Considerations

Liver Cirrhosis

• Hyponatremia in cirrhosis is associated with higher rates of complications including refractory ascites, spontaneous bacterial peritonitis, hepatic encephalopathy, and increased mortality 1
• Serum sodium has been incorporated into the MELD-Na score due to its prognostic importance 1
• Caution: Gastrointestinal bleeding risk is higher in cirrhotic patients treated with tolvaptan (10% vs 2% with placebo) 3

Neurosurgical Patients

• Fludrocortisone may be considered for hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm (Class I evidence) 2
• Hydrocortisone may prevent natriuresis in subarachnoid hemorrhage patients (Class I evidence) 2
• Important: Fluid restriction should NOT be used in subarachnoid hemorrhage patients at risk of vasospasm 2

Avoiding Complications

Osmotic Demyelination Syndrome

• Critical safety measure: Do not correct serum sodium by more than 8-10 mmol/L in the first 24 hours 1
• Risk factors: Chronic hyponatremia (>48 hours), alcoholism, malnutrition, liver disease, and hypokalemia 1
• Monitoring: If correction is too rapid, consider administering desmopressin and hypotonic fluids to re-lower sodium levels 4

Medication Considerations

• Tolvaptan: Monitor for hypernatremia, avoid in patients taking strong CYP3A inhibitors 3
• Diuretics: Monitor for worsening hypovolemia and electrolyte imbalances
• Hypertonic saline: Requires close monitoring to prevent overly rapid correction

Chronic Management

• Treat underlying causes (medication adjustment, management of heart failure or cirrhosis)
• Regular monitoring of serum sodium levels
• For mild chronic hyponatremia: Consider the impact on bone health, cognitive function, and fall risk 5

Hyponatremia management requires careful assessment of the underlying cause and appropriate, measured correction to avoid both the consequences of untreated hyponatremia and the complications of overly aggressive therapy.