What is the recommended rate and amount of hypertonic (high concentration) saline for treating severe hyponatremia (low sodium levels)?

Management of Hypertonic Saline for Hyponatremia

For severe symptomatic hyponatremia, administer 3% hypertonic saline with an initial goal to correct serum sodium by 6 mmol/L over 6 hours or until severe symptoms resolve, with total correction not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2

Initial Assessment and Treatment Based on Symptom Severity

Severe Symptoms (seizures, coma, severe neurological deficits)

• Administer 3% hypertonic saline immediately 1, 2, 3
• Initial goal: increase serum sodium by 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
• Monitor serum sodium every 2 hours during initial correction 1
• Consider ICU admission for close monitoring 2
• Discontinue 3% saline once severe symptoms resolve, then transition to protocols for mild symptoms or asymptomatic hyponatremia 4

Mild to Moderate Symptoms or Asymptomatic with Na <120 mmol/L

• Implement fluid restriction to 1 L/day as first-line treatment 1, 2
• Monitor sodium every 4 hours 2
• For SIADH: fluid restriction is the cornerstone of treatment 1
• For cerebral salt wasting: volume and sodium replacement is required instead of fluid restriction 1

Correction Rate Guidelines

• Do not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 4, 2
• After initial 6 mmol/L correction, limit to only 2 mmol/L in the following 18 hours 4
• For chronic hyponatremia (>48-72 hours), slower correction is safer after initial symptom control 4, 5
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): use more cautious correction rates of 4-6 mmol/L per day 1, 2

Calculation of Hypertonic Saline Dose

• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
• European guidelines recommend bolus-wise administration of 150 mL of 3% hypertonic saline 6
• Rapid correction (>1 mmol/L/h) should only be used for severely symptomatic and/or acute hyponatremia (≤48 hours) 4

Monitoring and Safety Considerations

• Monitor serum sodium every 2 hours during initial correction for severe symptoms 1, 2
• After severe symptoms resolve, monitor every 4 hours 4
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1
• Monitor urine output closely as diuresis correlates with degree of sodium overcorrection 6
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 5

Special Considerations

• Continue treatment until sodium reaches 131 mmol/L 4
• Exception: Subarachnoid hemorrhage patients receive treatment even for sodium levels of 131-135 mmol/L 4
• Distinguish between SIADH and cerebral salt wasting in neurosurgical patients, as treatment approaches differ significantly 1, 2
• Avoid fluid restriction in cerebral salt wasting as it can worsen outcomes 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours can lead to osmotic demyelination syndrome 1, 5
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting 1
• Failing to recognize and treat the underlying cause 1, 2
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1

Historical Perspective

• Earlier approaches from the 1980s suggested more aggressive correction rates (2.4 mmol/L/hour) 7
• Current guidelines are more conservative to prevent osmotic demyelination syndrome 1, 2, 5
• Historical recommendations suggested that if serum sodium is >105 mmol/L, it can be corrected to 125-130 mmol/L, but if <105 mmol/L, it should be raised by only 20 mmol/L 8