Normal adult blood loss of 400ml will not cause serious problems and should be analyzed objectively according to the patient’s age and the patient’s own physical condition.1. For elderly and frail patients with long-term chronic diseases such as low-protein malnutrition and anemia. At this time, the loss of 400ml of blood in a short period of time will cause the effective blood circulation in the patient’s body to decrease significantly, and the organism will show pre-expressions of hemorrhagic shock such as cold extremities, panic, chest tightness, rapid heartbeat, and decreased blood pressure, etc. At this time, the patient needs to be actively supplemented with crystalloid to maintain effective blood circulation and avoid the occurrence of serious complications. 2. If the patient is young and strong, healthy and without any basic diseases in daily life, the loss of 400ml of blood in 1 time will not have much effect on the human body, and the patient only needs to appropriately replenish water, pay attention to rest and avoid overexertion, and can quickly recover to normal body condition.