The results of sodium depletion are closely related to the state of water balance. If only sodium is lost and water is retained, serum sodium concentration eventually will decrease, as when water only is replaced following excessive sweating.
As a result water will migrate into the cells and symptoms of water intoxication develop: loss of appetite, weakness, mental apathy and muscle twitching.
If sodium loss is accompanied by water loss, symptoms of extra cellular fluid depletion develop: low blood volume, high hematocrit, collapse of veins, low blood pressure and muscle cramps. Most cases of dehydration seen in medical practice result from excessive loss of fluid from the gastrointestinal tract as a consequence of vomiting or diarrhea.
Following a reduction in body water, the only way to increase body water levels is to ingest fluid. This is largely controlled by the sensation of thirst although deviations in body water are not well detected by the thirst response. The thirst response is a complex concentration of physiological, psychological and behavioral factors.
Sodium depletion and water balance in human body
