Encyclopedia of Human Nutrition, Third Edition - Dehydration

An adequate water content is essential to maintain cellular homeostasis. Since there is a continuous turnover of body water, dehydration occurs when the water output (losses) is higher than the input (intake). Water is lost from the body primarily in urine, but also in feces, sweat, and evaporation from exhaled air. Dehydration most commonly occurs secondary to excess losses due to gastrointestinal illness (e.g., diarrhea) or impaired kidney function. It can also develop as a side effect of drugs, such as diuretics. Dehydration alters circulatory hemodynamics, impairs the heat transfer and thus may affect the core body temperature, and results in electrolyte and acid–base imbalances. Management of dehydration depends on the severity and on concurrent medical conditions. In mild-to-moderate cases, oral rehydration with adequate fluid solutions may be sufficient. In severe cases, or when gastrointestinal function is severely impaired, intravenous fluids may be required, along with appropriate electrolyte replacement.