Senile dehydration

Fluid loss exceeding fluid intake manifests clinically as decreased extracellular fluid volume, i.e., a hypovolemic state of insufficient fluid volume. Water loss is accompanied by sodium loss, and the degrees of the two losses may be unequal. When the proportion of water and sodium loss is consistent and extracellular fluid osmolality is maintained within the normal range, it is called isotonic dehydration; when water loss exceeds sodium loss, extracellular fluid osmolality >320 mmol/L, and serum sodium >150 mmol/L, it is called hypertonic dehydration; when sodium loss exceeds water loss, extracellular fluid osmolality <280 mmol/L, and serum sodium <130 mmol/L, it is called hypotonic dehydration. According to the amount of fluid loss, dehydration is divided into three degrees: moderate dehydration when water loss accounts for 3%–6% of body weight, and severe dehydration when water loss accounts for more than 6% of body weight. Dehydration is very common in the elderly and often coexists with other diseases. Common manifestations of dehydration in the elderly include weakness, dizziness, and personality changes. Although obvious dryness of the oral mucosa may be seen, the patient may not necessarily have obvious thirst sensation or increased drinking behavior. Severe cases often manifest as altered mental status (including hallucinations, delirium, lethargy, or coma), decreased urine output (though in dehydration caused by hypertonic diuresis, urine output may actually increase in the early stage), hypotension, and elevated hematocrit, but decreased skin turgor can also be seen in normal elderly individuals.