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
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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/