[Hyponatremia and physical exercise]

Exercise Associated Hyponatremia (EAH) is an occurrence of endurance sports that can cause severe clinical manifestations such as cerebral edema or respiratory failure. EAH is a dilutional hyponatremia, variant of SIADH, characterized by a plasma concentration of sodium lower than 135 mEq/l. Female gender and the duration of the competitions are associated with higher risk of hyponatremia. The incidence of hyponatremia, in fact, increases with duration, especially 4-8 hours after the start of the race. Women seem to be at greater risk than men. The pathophysiological mechanisms include increased loss of sodium through sweating and excessive intake of hypotonic fluids during and after the sporting event. In the genesis of EAH seems to have a decisive role the inadequate secretion of AVP by non osmotic stimuli, including IL-6. Indications for the prevention of hyponatremia include education of athletes for adequate consumption of fluids and monitoring of changes in body weight. Following the identification of electrolyte imbalance, the treatment requires a water restriction and infusion of hypertonic solutions 3%, especially in cases of severe hyponatremia. The effectiveness of the V2 receptor antagonists needs further investigation.