Patients with acute trauma, intra-abdominal hemorrhage, and hemorrhagic shock require aggressive surgical rehydration. The principle of rehydration is to first restore the patient’s blood volume, but not necessarily to transfuse blood. Crystalloid and colloid fluids, such as Ringer’s solution and saline, can be transfused. While restoring the patient’s blood volume quickly, then actively contact the blood bank for blood transfusion. Wait until the patient’s vital signs are stable before considering surgery. In case of major surgery, a very long fast is required. For example, radical surgery for gastric cancer or radical surgery for colon cancer usually requires 3-5 days of fasting. It is necessary to calculate the amount of fluid needed by the patient per day according to the patient’s weight. And based on the patient’s weight, the amount of calories the patient needs per day is calculated, which is routinely based on 25 kcal per kg of body weight. The input of fluids includes glucose, fatty milk, amino acids, as well as electrolytes and trace elements.