Near Drowning

causing hemodilution and possible hyponatremia and hypokalemia. The resultant change in plasma tonicity and electrolyte abnormalities can lead to secondary red cell hemolysis. This hemolysis by itself can impair oxygen delivery to the tissues. Fresh water, in addition to the hemodilution, also inactivates the surfactant within the alveoli. This alters alveolar surface tension and can result in alveolar collapse and pulmonary atelectasis. The ventilation/perfusion mismatch caused by perfused but unventilated lung regions causes hypoxemia, which can be severe. This can be potentiated by the mere presence of water in the alveoli and interstitium, acting as a diffusion barrier. This intrapulmonary shunting and barrier to oxygenation of the blood further hampers oxygenation of the tissues. In contrast, salt water pulls fluid into the alveoli because of its hypertonicity. This fluid comes from the vasculature, and if significant enough, it can cause a depletion of the intravascular fluid volume. Hypovolemia, hemoconcentration, and hypotension may result. This, in turn, can lead to decreased tissue perfusion and tissue hypoxia. Salt water does not inactivate the surfactant, so atelectasis is not typically a component of this syndrome. The electrolyte abnormalities involved in salt water aspiration are primarily hypernatremia, with a possible increase in serum calcium and magnesium based on the mineral content of the water. Despite the initiating physiology, the end pathology Peer Reviewed