The main components of body fluid are water and electrolytes. It is divided into two parts: cellular and extracellular fluid, and its amount varies with gender, age and fatness. The amount of body fluid in adult males is generally 60% of body weight; in adult females, the amount of body fluid is about 55% of body weight. Children have less fat, so the proportion of body fluid volume to body weight is higher, and in newborns, it can reach 80% of body weight. The amount of body fat increases with age, and after the age of 14, the proportion of body fluid to body weight in children is similar to that in adults. Imbalance of fluid balance can cause disturbance of the balance of the body. The body mainly through the kidney to maintain the balance of body fluids, to maintain the stability of the internal environment. The regulatory function of the kidney is influenced by neurological and endocrine responses. The normal pressure of body fluids is restored and maintained by the hypothalamic-posterior pituitary-antidiuretic hormone system, and then the blood volume is restored and maintained by the renin-aldosterone system. However, when blood volume is sharply reduced, the body will prioritize the maintenance and restoration of blood volume at the expense of maintenance of body fluid osmolarity, so that perfusion of vital organs is ensured and life is maintained. When the body loses water, there is an increase in extracellular fluid osmolality, which stimulates the hypothalamic-posterior pituitary-antidiuretic hormone system, producing thirst and increased water intake, as well as contributing to increased secretion of antidiuretic hormone. The epithelial cells of the distal tubule and collecting duct, under the effect of antidiuretic hormone, enhance water reabsorption, so that urine volume decreases and water is retained in the body, resulting in a decrease in extracellular fluid osmolality. Conversely, when water increases in the body, the extracellular fluid osmolality decreases, inhibiting the thirst response and decreasing the secretion of antidiuretic hormone. The reabsorption of water by the epithelial cells of the distal tubules and collecting ducts decreases and excess water is excreted from the body, increasing the extracellular fluid osmolality. This response of antidiuretic hormone secretion is very sensitive. When the plasma osmolality increases or decreases by less than 2% from normal, there is a change in the secretion of antidiuretic hormone, which keeps the body’s water dynamic and stable. Disorders of fluid metabolism and acid-base balance are often a concomitant symptom or result of a primary disease. Prompt measures should be taken to prevent the occurrence of such disorders. Generally, about 1500ml of 5% to 10% glucose solution, 500ml of 5% grape grain saline and 130-40ml of 10% KC can be given intravenously daily to replenish the daily requirement of water and glucose to conserve proteolytic metabolism and to avoid ketoacidosis that may occur when excess fat is burned. In patients with fever, the amount of supplementation can generally be increased according to the standard of about 3 to 5 ml/kg of hypotonic body fluid lost from the skin for every 1C0 increase in body temperature. Patients with moderate sweating lose about 500-1000ml of body fluid (containing 11.25-2.50g of NaC); with heavy sweating, about 1000-1500ml of body fluid is lost. patients with tracheotomy evaporate 2-3 times more water per day from breathing than normal, counting about 1000ml. All of them need to be increased in rehydration.