Dose of 3% Normal Saline for Severe Symptomatic Hyponatremia
For severe symptomatic hyponatremia (seizures, coma, altered mental status), administer 3% hypertonic saline as 100 mL boluses over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve, with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve. 1, 2
Initial Dosing Strategy
Bolus Administration:
- 100 mL of 3% saline over 10 minutes 2
- Can repeat up to 3 times at 10-minute intervals until symptoms improve 2
- Each 100 mL bolus raises sodium by approximately 1-2 mmol/L 1, 3
Alternative Continuous Infusion:
- Calculate using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) to determine total sodium deficit 1
- Infusion rate typically 0.5-2 mL/kg/hour of 3% saline for controlled correction 1
Target Correction Goals
Initial 6-Hour Period:
- Correct by 6 mmol/L over first 6 hours or until severe symptoms resolve 1, 4, 3
- This 4-6 mmol/L increase is adequate for the most seriously ill patients 3
24-Hour Maximum:
- Total correction must not exceed 8 mmol/L in 24 hours 1, 4, 3
- If 6 mmol/L corrected in first 6 hours, only 2 mmol/L additional correction allowed in next 18 hours 1, 4
Extended Correction Limits:
- 48 hours: 12-14 mmol/L maximum (not exceeding 18 mmol/L) 3
- 72 hours: 14-16 mmol/L maximum (not exceeding 20 mmol/L) 3
Monitoring Requirements
Severe Symptoms:
- Check serum sodium every 2 hours during initial correction phase 1, 4
- Monitor urine output continuously 3
After Symptom Resolution:
When to Discontinue 3% Saline
Stop 3% saline when: 4
- Severe symptoms resolve (seizures stop, consciousness improves)
- 6 mmol/L correction achieved in first 6 hours
- Total 8 mmol/L correction reached in 24 hours
Transition after discontinuation: 4
- Switch to fluid restriction of 1 L/day for SIADH 1, 4
- Continue isotonic or hypertonic saline for cerebral salt wasting 1
- Add oral sodium chloride 100 mEq three times daily if needed 1
High-Risk Populations Requiring Slower Correction
Limit to 4-6 mmol/L per day (not exceeding 8 mmol/L in 24 hours) for: 1, 3
- Advanced liver disease
- Chronic alcoholism
- Malnutrition
- Prior encephalopathy
- Severe hyponatremia (<120 mmol/L)
- Hypokalemia
Alternative Oral Route
For patients unable to access ICU or when IV access is problematic, hourly oral NaCl tablets calculated to deliver equivalent of 0.5 mL/kg/hour of 3% NaCl can provide predictable correction with careful monitoring 5
Critical Safety Considerations
Osmotic Demyelination Syndrome Prevention:
- Overcorrection defined as >10 mmol/L in 24 hours, >18 mmol/L in 48 hours, or >20 mmol/L in 72 hours 3
- If overcorrection occurs, immediately administer desmopressin to terminate water diuresis and consider D5W to relower sodium 1, 3
Peripheral vs Central Access:
- 3% saline can be safely administered peripherally with low complication rates (infiltration 3.3%, phlebitis 6.2%) 6
- Central line not mandatory but may be preferred for prolonged infusions 6
Common Pitfall: