Rehydration principles for fasting patients: First, the volume of rehydration fluid, generally speaking, the normal daily physiological requirement of the human body is 40 ml per kg of body weight per day, for example, the daily basic rehydration volume for a 60 kg person should be more than 2400 ml, and if fever occurs, every 1°C increase usually requires another 5 ml per kg of body weight or so. Second, we should also pay attention to ensure the nutritional status of the patient, that is, the energy supply of sugar, fat and amino acids. The daily energy requirement of the human body is normally 25 calories per kilogram of body weight per day, and the daily calorie requirement of a 60kg patient is 1500 calories, according to the sugar-fat ratio of 6:4, the energy provided by glucose should be 1000 calories, and the energy provided by fat should be 600 calories The energy provided by fat should be around 600 calories. Third, it is also necessary to ensure the water-electrolyte balance, supplementing the daily physiological requirements of sodium chloride 4.5g and potassium chloride 3g, and adding the necessary vitamins and trace elements.