[Physiopathology of accidental drowning].

The first phase of accidental drowning begins with asphyxia, due to either laryngospasm (10-15 percent of cases) or water aspiration. The second phase is characterized by water and electrolyte changes in the blood. The physiopathological modifications caused by drowning in fresh water differ from those of drowning in sea water. The hypotonic fresh water quickly diffuses in the bloodstream. The consequences are, in many cases, hypervolemia with pulmonary edema, hemolysis, hyperkalemia with risk of ventricular fibrillation, diminution of hemoglobin, and a relative decrease in plasma concentration of Na, Cl, Ca, and albumin. Further, inactivation and washing out of the anti-atelectasis factor from the alveoli by fresh water facilitate the formation of atelectasis. In cases of accidental drowing in sea water the osmotic gradient is in inverse: the electrolytes of aspirated salt water diffuse in the circulation, whereas the blood serum and the plasma albumin pass into the alveoli. Acute pulmonary edema often follows these pathological changes. Hypovolemia with circulatory collapse, hemoconcentration with rise in hemoglobin, hematocrit, sodium, potassium and albumin, and, finally, an elevated risk of thromboembolism due to increased blood viscosity, represent further complications. On the other hand, ventricular fibrillation is rare, hemolysis is absent and atelectasis usually does not occur.