Question

At our institution we have developed a guideline for the use of hypertonic saline in hyponatremia.

Administration of 3% sodium chloride for acute or symptomatic hyponatremia

• Bolus doses are preferred over continuous infusion.
• Use in patients with rapid decline in serum sodium levels (>= 10 mEq decrease over 24 hours) or symptomatic (e.g. seizures).
• Do not attempt to normalize the serum sodium level in the first 24 hours.
• Serum sodium correction should be no more than 8-10 mEq/L in a 24-hour period.
  • 8 mEq/L (or less) should be used in patients at high risk for osmotic demyelination syndrome
  • High risk populations: chronic hyponatremia, hypokalemia, alcoholism, malnutrition, or liver disease
• Chronic hyponatremia should be corrected over days with a goal of 4-8 mEq/L in 24 hours.
  • Fluid restriction should be considered first-line for chronic hyponatremia.

Acute hyponatremia with severe symptoms

• Bolus 3% sodium chloride 150 mL over 10 minutes.
• If symptoms persist repeat up to 3 doses over 30 minutes.

Acute hyponatremia with moderate symptoms

• Bolus 3% sodium chloride 150 mL over 20 minutes once.

Hyponatremia Fluid Rate Calculations (**Be Careful with Online Calculators**)

FYI: 3% Sodium Chloride (1.95 mL/mEq; 513 mEq/1 L); 0.9% Sodium Chloride (6.5 mL/mEq; 154 mEq/1 L)

Equations for Calculations

1. Sodium correction for HYPERglycemia
   1. Corrected Na=Observed Na + 0.016 x (serum glucose-100)
2. Calculated Sodium Deficit
   1. Female: (Desired Na – Observed Na) x 0.5 L/kg x weight (kg)
   2. Male: (Desired Na – Observed Na) x 0.6 L/kg x weight (kg)
   3. This equation will give you the total mEq of Na needed in 24 hours.
   4. Remember: Correction should be no more than 8 mEq/L in 24 hours in most cases.
3. Calculated Infusion Rate for Sodium Correction
   1. ___ mEq Na required (from Equation 2) x ___ mL/mEq of fluid = ___ mL of fluid
   2. ___ mL of fluid / 24 hours = ___ mL/hr of fluid

***See Visual Diagnosis for an Example with Calculations***

Answer

Example:

70 kg male patient with a current sodium of 115 mEq/L (not hyperglycemic)

3% Sodium Chloride

1. Not hyperglycemic
2. Calculated sodium deficit
   1. Male: (123 mEq – 115 mEq) x 0.6 L/kg x 70 kg=336 mEq deficit of Na
3. Infusion rate calculation
   1. 336 mEq Na x 1.95 mL/mEq (3% sodium chloride) = 655 mL 3% required
   2. 655 mL 3% / 24 hours = 27 mL/hr

0.9% Sodium Chloride

1. Not hyperglycemic
2. Calculated sodium deficit
   1. Male: (123 mEq – 115 mEq) x 0.6 L/kg x 70 kg = 336 mEq deficit of Na
3. Infusion rate calculation
   1. 336 mEq Na x 6.5 mL/mEq (0.9% sodium chloride) = 2184 mL 0.9% required
   2. 2184 mL 0.9% / 24 hours = 91 mL/hr

**Popular Online Calculator Using Same Example**

3% sodium chloride: 54 mL/hr

0.9% sodium chloride: 551 mL/hr

Be aware that the default setting of the calculator is to correct by 12 mEq/L over 24 hours leading to larger rates of infusion.

References

Adult Hypertonic Aline for Use in Hyponatremia, Medication Use Guideline. University of Maryland Medical System. Accessed July 2024.

Hoorn EJ, Zietse R. Diagnosis and treatment of hyponatremia: compilation of the guidelines.
JASN. 2017; 28(5):1340-1349.

Jones GN, Bode L, Riha H et al. Safety of continuous peripheral infusion of 3% sodium chloride solution in neurocritical care patients. Am J Crit Care. 2017; 26(1): 37-42.

Sodium chloride preparations. Lexi-Drugs. Lexicomp. Wolters Kluwer Health, Inc. Riverwoods, IL. Available at: http://online.lexi.com. Accessed June 2018.

Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatremia. Intensive Care Med. 2014; 40:320-331.

Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, Evaluation and Treatment of Hyponatremia: Expert Panel Recommendations. Amer J Med. 2013; 126:S1-S42.