Treatment of Hyponatremia:

For severe neurologic symptoms (seizures, coma, impending brain herniation) or with Na < 120 mEq/L, start 3% hypertonic saline (513 mEq/L of Na)

• Start with infusion of 100 ml and repeat up to a total of 300 ml
• STOP when symptoms improve or when serum Na rises by 4-6 mEq/L

For mild or moderate symptoms or Na between 120-130

• Use 0.9% normal saline (154 mEq/L of Na)
• Free water restriction (500-1000mL/day)
• Correct underlying etiology of hyponatremia when possible
• Stop any contributing drugs such as diuretics, SSRIs, phenothiazines, cyclophosphamide, desmopressin, amiodarone, opiates, carbamazepine
• Volume repletion in hypovolemic patients
• Correct hypokalemia

Calculating the expected change in Na after one liter of fluids to avoid overcorrection:

Androgue and Madias formula

Expected change in Na = (Infused Na - serum Na)/(TBW + 1)

• TBW = total body water = approximately 60% of weight in kg

Do not correct faster than 0.5 mEq/L/hour or 12 mEq/L24 hrs

Frequent monitoring of Na concentration during treatment is important to avoid overcorrection

To make it easy, just use this Medcalc formula which crunches the numbers for you:

http://www.medcalc.com/sodium.html

Osmotic demyelination syndrome:

Complication of treatment when Na is corrected too rapidly

• Dysarthria, dysphagia, lethargy, paraparesis, quadriparesis, seizures, coma

References:

Petrino, Roberta, and Roberta Marino.. "Fluids and Electrolytes." Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8eEds. Judith E. Tintinalli, et al. New York, NY: McGraw-Hill, 2016, pg 95-97.

Mount, David B.. "Fluid and Electrolyte Disturbances." Harrison's Principles of Internal Medicine, 19eEds. Dennis Kasper, et al. New York, NY: McGraw-Hill, 2014, http://accessmedicine.mhmedical.com.ezproxy.rowan.edu/content.aspx?bookid=1130&sectionid=79726591.