How should hyponatremia be treated?

Treatment of Hyponatremia (Na 130)

Treatment of hyponatremia should be based on the underlying cause and volume status, with correction rates not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Classification and Diagnostic Approach

The first step in managing hyponatremia is determining the patient's volume status:

• Hypovolemic hyponatremia: Decreased extracellular fluid volume

  • Causes: Diuretic use, dehydration, gastrointestinal losses
  • Labs: Urine sodium <20 mEq/L, elevated BUN/creatinine ratio

• Euvolemic hyponatremia: Normal extracellular fluid volume

  • Primary cause: SIADH (Syndrome of Inappropriate ADH)
  • Labs: Urine osmolality >500 mOsm/kg, urine sodium >20-40 mEq/L

• Hypervolemic hyponatremia: Increased extracellular fluid volume

  • Causes: Cirrhosis, heart failure, nephrotic syndrome
  • Labs: Urine sodium <20 mEq/L, elevated BUN/creatinine ratio

Treatment Algorithm Based on Volume Status

1. Hypovolemic Hyponatremia

• Primary treatment: Isotonic (0.9%) saline infusion for plasma volume expansion 1
• Discontinue diuretics or other causative medications
• Reassess sodium levels after volume status correction

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

• Primary treatment: Fluid restriction (1-1.5 L/day) 2, 1
• Increase solute intake (salt and protein)
• Consider oral sodium chloride tablets if no response to fluid restriction
• For refractory cases:
  • Tolvaptan (vasopressin receptor antagonist) starting at 15 mg once daily, can be titrated up to 60 mg daily 3
  • Oral urea (30-60 g/day) can be considered as an alternative 1

3. Hypervolemic Hyponatremia (e.g., cirrhosis, heart failure)

• Primary treatment: Fluid restriction to 1,000 mL/day 2, 1
• Treat underlying condition (heart failure, cirrhosis)
• Consider loop diuretics for volume management
• Albumin infusion may improve serum sodium concentration in cirrhotic patients 2, 1
• For severe or refractory cases, consider tolvaptan (with caution in liver disease) 3

Correction Rates and Monitoring

• Maximum correction rate: 8 mmol/L in 24 hours for chronic hyponatremia 2, 1
• Target correction with 3% hypertonic saline: 4-6 mmol/L in first 6 hours or until symptoms improve 1
• High-risk patients (alcoholism, malnutrition, liver disease): Lower correction rate of 4-6 mmol/L per day 1
• Monitoring: Check serum sodium every 4-6 hours during active correction, every 2 hours in severe cases 1
• If correction exceeds 8 mmol/L in 24 hours, consider administration of hypotonic fluids or desmopressin to prevent osmotic demyelination syndrome 1

Special Considerations for Cirrhotic Patients

In patients with liver cirrhosis and hyponatremia:

• Hyponatremia is defined as serum sodium <130 mmol/L 2
• Complications increase significantly below this level, including:
  • Spontaneous bacterial peritonitis (OR 3.40)
  • Hepatorenal syndrome (OR 3.45)
  • Hepatic encephalopathy (OR 2.36) 2
• Discontinue diuretics if hypovolemic hyponatremia is suspected 2
• Avoid hypertonic saline unless severe neurological symptoms are present, as it can worsen ascites and edema 2

Potential Pitfalls and Caveats

• Misdiagnosis of volume status can lead to inappropriate treatment
• Overly rapid correction can lead to osmotic demyelination syndrome
• Cerebral salt wasting should be distinguished from SIADH in neurosurgical patients 2
• Vaptans should be used with caution in liver disease due to risk of gastrointestinal bleeding (10% vs 2% with placebo) 3
• Regular monitoring of electrolytes during recovery is necessary to prevent complications 1
• Even mild chronic hyponatremia is associated with cognitive impairment, gait disturbances, and increased rates of falls and fractures 4

By following this structured approach based on volume status and carefully monitoring correction rates, hyponatremia can be safely and effectively managed while minimizing the risk of complications.