Hypertonic Sodium 3% Infusion Rate for Severe Symptomatic Hyponatremia
For severe symptomatic hyponatremia, 3% hypertonic saline should be administered with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve, with a maximum correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2
Initial Management Based on Symptom Severity
Severe Symptoms (seizures, coma, severe neurological symptoms)
- Administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
- Initial infusion rate can be calculated as: body weight (kg) × desired rate of increase in sodium (mmol/L per hour) 3
- After initial 6 mmol/L correction, limit to only 2 mmol/L in the following 18 hours 2
- Discontinue 3% hypertonic saline once severe symptoms resolve 2
- Monitor serum sodium every 2 hours during initial correction 1
Moderate to Mild Symptoms
- For less severe symptoms, transition to fluid restriction of 1L/day after resolution of severe symptoms 1, 2
- Consider oral sodium supplementation (NaCl 100 mEq orally three times daily) for mild symptoms 4
- Monitor serum sodium every 4 hours after resolution of severe symptoms 2
Critical Safety Parameters
- Total correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2, 4
- Rapid correction (>1 mmol/L/h) should only be used for severely symptomatic and/or acute hyponatremia (≤48 hours) 2
- For chronic hyponatremia (>48-72 hours), slower correction is safer after initial symptom control 2
- Patients with advanced liver disease, alcoholism, malnutrition require even more cautious correction (4-6 mmol/L per day) 1, 4
Special Considerations
- For cerebral salt wasting (CSW), treatment focuses on volume and sodium replacement with 3% hypertonic saline and fludrocortisone for severe symptoms 1
- In subarachnoid hemorrhage patients at risk for vasospasm, avoid fluid restriction 1, 4
- For patients with cirrhosis and severe hyponatremia, use even more cautious correction rates (4-6 mmol/L per day) 1
- Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1
Management After Initial Correction
- After severe symptoms resolve, switch to protocols for mild symptoms or asymptomatic hyponatremia 2
- Continue treatment until sodium reaches 131 mmol/L 2
- Exception: Subarachnoid hemorrhage patients receive treatment even for sodium levels of 131-135 mmol/L 2
Risk of Overcorrection
- Monitor for spontaneous water diuresis which can lead to overcorrection 5
- If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 6
- The risk of overcorrection is higher in severely symptomatic patients 4
Recent Evidence
Recent guidelines emphasize that rapid intermittent administration of hypertonic saline is preferred for treatment of symptomatic hyponatremia, with bolus infusions of 100-150 ml of 3% saline rather than continuous infusion 5.