What is the recommended dose of 3% saline solution (3% sodium chloride solution) in milliliters per kilogram of body weight for treating severe hyponatremia?

3% Hypertonic Saline Dosing for Severe Hyponatremia

For severe symptomatic hyponatremia, 3% hypertonic saline should be administered as boluses of 100-150 mL intravenously, with the goal of increasing serum sodium by 4-6 mEq/L within the first 1-2 hours to alleviate severe symptoms. 1

Dosing Considerations

• Initial bolus approach:

  • 100-150 mL of 3% hypertonic saline administered intravenously 1
  • Monitor serum sodium levels within 6 hours of administration 2
  • Target increase: 1-2 mEq/L per hour until symptoms abate 3

• Maximum correction limits:

  • Do not exceed 12 mEq/L in 24 hours 3, 4
  • Do not exceed 18 mEq/L in 48 hours 3
  • Exceeding these limits risks osmotic demyelination syndrome

Calculation Method

For continuous infusion when needed, the infusion rate can be estimated using:

• Body weight (kg) × desired rate of increase in sodium (mEq/L per hour) 3
• This formula provides the infusion rate in mL/kg per hour

Clinical Approach Based on Symptom Severity

Severely Symptomatic Hyponatremia

• Symptoms: Somnolence, obtundation, coma, seizures, or cardiorespiratory distress 4
• Approach: Emergency treatment with bolus hypertonic saline
• Goal: Increase serum sodium by 4-6 mEq/L within 1-2 hours 4
• Caution: Stop treatment once symptoms abate or after reaching the correction limit

Moderately Symptomatic Hyponatremia

• Symptoms: Nausea, vomiting, headache, confusion
• Approach: Less aggressive correction with 3% saline
• Goal: Increase serum sodium by 0.5-1 mEq/L per hour 5

Asymptomatic Hyponatremia

• Approach: Fluid restriction may be sufficient 5
• Goal: Gradual correction without hypertonic saline

Monitoring and Safety

• Frequent serum sodium measurements (every 2-4 hours initially)
• Be prepared to slow or stop treatment if correction exceeds 0.5 mEq/L per hour in chronic cases 5
• Have hypotonic fluids or desmopressin available to manage overcorrection 1

Special Considerations

• Patients with alcoholism, malnutrition, or liver disease are at higher risk for osmotic demyelination syndrome and require more cautious correction 2
• Re-administration should not occur until serum sodium is <155 mmol/L 2
• Rapid intermittent administration is preferred over continuous infusion for symptomatic hyponatremia 1

The treatment approach must balance the risks of untreated severe hyponatremia against the risks of overly rapid correction, with the primary goal of alleviating severe neurological symptoms while preventing osmotic demyelination syndrome.