Kins 714: Exertional Hyponatremia

physiological hyponatremia

sodium deficiency in which plasma sodium concentration is at least less than 135 mEq and may or may not be accompanied by symptoms of hyponatremia

symptomatic exertional hyponatremia

sodium deficiency that involves a plasma sodium concentration of less than 130 mEq and is accompanied with typical symptoms.

hypervolemic hyponatremia

an excess of total body water (fluid overload) with an expanded extracellular fluid volume and increased whole0body sodium

• common sign of this condition is extremity edema

hypovolemic hyponatremia

a reduced extracellular volume with deficits of total body sodium and water

etiology

pathophysiology

when a large volume of hypotonic fluid is consumed, the extracellular fluid becomes dilute because the fluid moves from the intestine directly into the blood

as extracellular tonicity falls, water flows into cells and they swell

brain edema usually accompanies severe EHs

predisposing factors

• a large volume of hypotonic fluid is consumed within a few hours

• sodium losses in sweat and urine not replaced

• absence of heat acclimatization

• exercise duration

• premeditate drinking large volumes of water pre exercise

• genetic tendency for high sweat concentration

• female hikers and marathon runners were more likely than males

prevention

• consume fluids during exercises to not exceed weight loss over 2%

• consume ample dietary Na when training in hot environment and as a part of daily meals

• acclimatize to heat

• consume salty foods with water during long duration events, and avoid overconsumption

• educate athletes of risk of extertional hyponatremia

• do not gain weight during exercising by overhydrating

recognition

key differential is blood Na assessment which should be measured in collapsed athletes in medical tent

clinical symptoms combined with blood Na concentration warrant diagnosis

medical emergency

complications of correcting hyponatremia

normal saline administration does not correct fluid overload and is contraindicated for EH (need 3% hypertonic saline)

central pontine myelinolysis (CPM): brain dysfunction caused by destruction of the myelin sheath of nerve cells within the brain stem. this occurs most often when low blood sodium levels are corrected too quickly via hypertonic intravenous saline.

recovery

when treated appropriately with IV hypertonic saline EH spontaneously resolves without complications

chronic morbidity is rare

rapid recognition and appropriate treatment reduce the risk of encephalopathy or CN damage