Sodium Concentration in 3% NaCl Solution
A 3% sodium chloride solution contains 513 mmol/L of sodium (or 513 mEq/L).
Calculation Method
To determine the sodium concentration in any NaCl solution, use the following approach 1:
- 3% NaCl means 3 grams of NaCl per 100 mL of solution 1
- Molecular weight of NaCl = 58.5 g/mol 1
- Calculation: (3 g / 58.5 g/mol) × (1000 mL / 100 mL) = 513 mmol/L 1
Since sodium chloride dissociates 1:1 into sodium and chloride ions, this equals 513 mmol/L of sodium and 513 mmol/L of chloride 1.
Clinical Context for 3% Hypertonic Saline
Primary Indication
- 3% hypertonic saline is indicated for severe symptomatic hyponatremia with neurological manifestations such as seizures, altered mental status, or coma 1, 2
Standard Dosing Protocol
- Administer 100 mL boluses of 3% NaCl intravenously over 10 minutes, repeating up to three times at 10-minute intervals for severe symptomatic hyponatremia 1
- Target an initial correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1
- Never exceed 8 mmol/L correction in any 24-hour period to prevent osmotic demyelination syndrome 1
Alternative Continuous Infusion
- A continuous infusion of 500 mL of 3% NaCl over 6 hours through a peripheral vein has been shown effective in reversing hyponatremic encephalopathy without producing cerebral demyelination 2
- In one case series of 71 episodes, this protocol increased mean serum sodium from 114.1 mEq/L to 117.9 mEq/L at 3 hours and 128.3 mEq/L at 48 hours, with marked symptom improvement in 97% of cases 2
Safety Considerations
- Peripheral administration of 3% saline is safe, with low complication rates: infiltration 3.3%, phlebitis 6.2%, erythema 2.3%, edema 1.8%, and venous thrombosis 1% 1
- Monitor serum sodium every 2 hours during initial correction for severe symptoms 1
- High-risk patients (advanced liver disease, alcoholism, malnutrition) require even more cautious correction at 4-6 mmol/L per day maximum 1