Rate of Sodium Increase with 3% NaCl at 10 mL/hour
Administering 3% NaCl at 10 mL/hour will increase serum sodium by approximately 0.5-1 mEq/L per hour, though this rate varies significantly based on patient factors including volume status, ongoing losses, and renal function. 1
Calculation Basis
3% NaCl contains 513 mEq of sodium per liter (or 5.13 mEq per 10 mL), meaning that 10 mL/hour delivers approximately 5.13 mEq of sodium per hour to the patient 1
The actual increase in serum sodium depends on the patient's total body water (TBW), which equals approximately 0.6 × body weight in kg for adult males 2
For a 70 kg patient with TBW of 42 liters, delivering 5.13 mEq/hour would theoretically increase serum sodium by approximately 0.12 mEq/L per hour if distributed evenly, but clinical studies show higher rates due to concurrent fluid losses and diuresis 1
Clinical Evidence from Practice
In hospitalized heart failure patients with hyponatremia, continuous infusion of 3% NaCl at 10 mL/hour successfully corrected hyponatremia without causing hypernatremia or heart failure exacerbation 1
This infusion rate is considerably slower than emergency bolus protocols, where 100-250 mL boluses of 3% NaCl increase sodium by 5 mmol/L within 4 hours 3
The slower continuous infusion approach (10 mL/hour) provides more controlled correction, reducing overcorrection risk compared to rapid bolus therapy 3, 4
Critical Safety Parameters
Serum sodium must be monitored every 2-4 hours during active correction to ensure safe correction rates are maintained 5
Maximum safe correction limits are 6 mmol/L in 6 hours, 12 mmol/L in 24 hours, or 18 mmol/L in 48 hours to prevent osmotic demyelination syndrome 5
Serum osmolality changes must not exceed 3 mOsm/kg/hour to prevent cerebral edema 2, 5, 6
Important Clinical Caveats
Patients with lower initial sodium levels (<115 mEq/L) have significantly higher risk of overcorrection with an adjusted odds ratio of 0.84 per 1 mEq/L increase in baseline sodium 4
Early urine output and the sodium increase during the first 4 hours are critical predictors of overcorrection risk—higher early increases correlate with overcorrection 4
In patients receiving concurrent diuretics, the effective sodium increase may be higher than calculated due to free water losses exceeding sodium losses 1
Volume status significantly impacts the response: hypovolemic patients may have more rapid correction as volume is restored, while hypervolemic patients (e.g., heart failure) may have slower correction 5, 1