Hyponatremia Review Question

A 60kg female patient is seizing and has a serum sodium of 113 mEq/L with no underlying history of seizures. What should be the treatment of her hyponatremia?

A. Hypertonic saline 3% – 290 ml over 2 hours
B. Normal saline 3% – 50 ml over 30 minutes
C. Phenytoin 1 gram
D. Hypertonic saline 3% – 1000 ml IV bolus
E. Hypertonic saline 3% – 750 ml over 2 hours

Read more questions from the Kaji Review

Show Answer

Answer: A

To acutely stop seizure activity in a hyponatremic patient, you will need to raise the serum sodium by 5 mEq/liter of total body water (TBW). 290 mL of hypertonic saline will allow for an  increase serum sodium by 5 mEq/L (could be administered as 145 mL/h for 2 h).

  • The Sodium Requirement (mEq) = TBW x (Desired Na – Serum Na) where TBW = Body Weight x 0.6 (for men) or 0.5 (for women).


  • 3% hypertonic saline has 513 mEq of Na per liter.


  • Volume of Hypertonic Saline = Na Requirement (mEq)/Infusate Na Concentration (mEq/L)


  • In a 60-kg woman with serum sodium level of 113 mEq/L, the amount required is 0.5x60x5=150mEq of Na. 150/513 = 292ml of 3% hypertonic saline.


  • In general, 200-400 mL of 3% NaCl is reasonable dose in most adult patients with severe symptomatic hyponatremia, which may be given IV over 1-2 hr until resolution of seizures.  Alternatively 2 cc/kg  of 3% over 10-60 minutes can be infused with a repeat of up to 3 times.


  • Moritz ML, Ayus JC. 100cc 3% sodium chloride bolus: a novel treatment for hyponatremic encephalopathy. Metab Brain Dis. 2010 Mar; 25(1): 91-6.
  • EmCrit.org – Severe Hyponatremia http://emcrit.org/podcasts/hyponatremia/

Leave a Reply