3% NaCl Administration for Severe Hyponatremia
For severe symptomatic hyponatremia (seizures, coma, altered mental status), administer 3% hypertonic saline as a 100 mL bolus over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms resolve, with a target correction of 6 mmol/L over 6 hours. 1, 2
Initial Bolus Dosing Strategy
Standard Bolus Protocol
- Administer 100 mL of 3% NaCl over 10 minutes as the initial bolus 1, 2
- Repeat the 100 mL bolus every 10 minutes if severe symptoms persist, up to a maximum of three boluses 1, 2
- Alternative approach: 250 mL bolus may be more effective than 100 mL (52% vs 32% achieving ≥5 mmol/L rise within 4 hours) without increasing overcorrection risk 3
Target Correction Goals
- Initial goal: Increase serum sodium by 6 mmol/L over the first 6 hours OR until severe symptoms resolve 1, 2
- Maximum correction: Do not exceed 8 mmol/L in 24 hours 1, 2
- After achieving the initial 6 mmol/L correction, limit further correction to only 2 mmol/L in the following 18 hours 4
Continuous Infusion Dosing (Alternative to Bolus)
Calculation Method
- Infusion rate (mL/kg/hour) = Body weight (kg) × Desired rate of sodium increase (mmol/L/hour) 5
- Target rate: 1-2 mmol/L per hour until symptoms abate 5
- Do not exceed total correction of 12 mmol/L in 24 hours or 18 mmol/L in 48 hours 5
Practical Example
- For a 70 kg patient targeting 1 mmol/L/hour increase: 70 kg × 1 mmol/L/hour = 70 mL/hour of 3% NaCl 5
Monitoring Requirements
Frequency of Sodium Checks
- Every 2 hours during initial correction phase (first 6 hours) 1
- Every 4 hours after severe symptoms resolve 1, 4
- Daily monitoring once sodium reaches 131 mmol/L 4
When to Discontinue 3% Saline
- Stop when severe symptoms resolve 4
- Stop when sodium has increased by 6 mmol/L in the first 6 hours 4
- Stop when total correction approaches 8 mmol/L in 24 hours 1, 4
- Transition to fluid restriction (1 L/day) and mild symptom protocol after discontinuation 4
High-Risk Populations Requiring Slower Correction
Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require more cautious correction at 4-6 mmol/L per day (not per 24 hours) 1
These patients have significantly higher risk of osmotic demyelination syndrome and should not exceed 8 mmol/L total correction in 24 hours 1
Critical Safety Parameters
Osmotic Demyelination Prevention
- Never exceed 8 mmol/L correction in 24 hours for chronic hyponatremia (>48 hours duration) 1, 2
- Never exceed 25 mmol/L correction in 48 hours 2
- Never correct past 140 mmol/L 2
- Risk factors for demyelination: chronic liver disease, hypoxic episode, correction >25 mmol/L in 48 hours 2
Overcorrection Management
- If sodium rises >8 mmol/L in 24 hours, immediately discontinue 3% saline 1
- Switch to D5W (5% dextrose in water) to relower sodium 1
- Consider desmopressin to slow or reverse rapid rise 1
Special Clinical Scenarios
Acute vs Chronic Hyponatremia
- Acute hyponatremia (<48 hours): Can tolerate faster correction (1-2 mmol/L/hour) without demyelination risk 1, 4
- Chronic hyponatremia (>48 hours): Requires slower correction after initial symptom control 4
Neurosurgical Patients
- Continue treatment even for sodium 131-135 mmol/L in subarachnoid hemorrhage patients at risk for vasospasm 4
- Distinguish cerebral salt wasting from SIADH, as both may require 3% saline but have different underlying pathophysiology 1
Common Pitfalls to Avoid
- Waiting for ICU transfer before initiating 3% saline in severe symptomatic hyponatremia - treatment should begin immediately 2
- Inadequate monitoring during active correction - sodium must be checked every 2 hours initially 1
- Continuing 3% saline after symptoms resolve - transition to maintenance therapy once initial goals achieved 4
- Using 3% saline in hypervolemic hyponatremia without life-threatening symptoms - fluid restriction is preferred 1