How is hyponatremia treated?

Treatment of Hyponatremia

The treatment of hyponatremia should be tailored to the patient's volume status, severity of symptoms, and underlying cause, with correction rates not exceeding 8 mEq/L in 24 hours to prevent Osmotic Demyelination Syndrome (ODS). 1

Classification and Initial Assessment

Hyponatremia is classified based on volume status:

1. Hypovolemic hyponatremia: Treated with normal saline infusion 1
2. Euvolemic hyponatremia: Often due to SIADH, treated with fluid restriction and possibly tolvaptan 1, 2
3. Hypervolemic hyponatremia: Treated with fluid restriction and management of underlying condition (heart failure, cirrhosis) 1

Key diagnostic parameters:

• Serum sodium level (severity: mild 130-134 mEq/L, moderate 125-129 mEq/L, severe <125 mEq/L) 3
• Urine osmolality and sodium concentration 1
• Assessment of symptoms (mild: nausea, headache, weakness; severe: seizures, delirium, coma) 4

Treatment Algorithm Based on Severity and Symptoms

Severe Symptomatic Hyponatremia (Medical Emergency)

• 3% hypertonic saline boluses to increase serum sodium by 4-6 mEq/L in the first few hours 1
• Goal: Not exceeding 8 mEq/L in 24 hours 1
• Target sodium level should not exceed 123 mEq/L in first 24 hours for severe hyponatremia 1
• Monitor serum sodium every 2-4 hours initially 1

Chronic Hyponatremia due to SIADH

1. First-line: Fluid restriction to 1-1.5 L/day 1
2. For non-responders: Tolvaptan starting at 15 mg once daily 1, 2
   • Clinical trials show tolvaptan increases serum sodium by 4-6 mEq/L in first 24 hours 2
   • Must be initiated in hospital setting with close monitoring 1
   • Particularly effective for patients with sodium <130 mEq/L 2

Hypovolemic Hyponatremia

• Normal saline infusion to correct volume deficit 1
• Sodium chloride supplementation at 1-3 mmol/kg/day for adults 1

Hypervolemic Hyponatremia

• Fluid restriction and treatment of underlying condition 1
• Consider spironolactone (starting at 100 mg, up to 400 mg) for heart failure or cirrhosis 1

Monitoring and Prevention of Complications

• Monitor serum sodium every 2-4 hours initially, then every 4-6 hours once stabilized 1
• Monitor vital signs every 1-2 hours initially 1
• Daily renal function tests and electrolytes with each sodium check 1

Important Cautions

• Avoid overcorrection: Risk of Osmotic Demyelination Syndrome (ODS) if correction exceeds 8 mEq/L in 24 hours 1, 4
• High-risk patients for ODS: Those with alcoholism, malnutrition, liver disease, severe hyponatremia, metabolic derangements, low cholesterol, and prior encephalopathy 1
• Consider desmopressin (1-2 μg IV/SC every 6-8 hours) to slow correction if rate exceeds 8 mEq/L in 24 hours 1
• Volume overload in CHF can be worsened by hypertonic saline; consider lower volumes and concurrent diuretics 1

Alternative Therapies

• Urea: Effective alternative to vaptans with lower risk of liver injury 1
• Demeclocycline: Alternative when other options unavailable, but has potential side effects 1
• Loop diuretics: Useful in managing edematous hyponatremic states 5

Special Populations

• Elderly patients: Particularly susceptible to hyponatremia; chronic mild hyponatremia associated with cognitive impairment, gait disturbances, increased falls and fractures 1
• Patients with liver disease: Require more cautious correction 1

Remember that even mild chronic hyponatremia can lead to significant morbidity, including cognitive impairment, gait disturbances, and increased risk of falls and fractures 4. Treatment should always address the underlying cause while carefully managing the serum sodium level.