Pathophysiology during extracorporeal circulation. Due to the presence of low temperature, low flow, altered blood flow pattern due to advective perfusion during extracorporeal circulation and the production of inflammatory mediators caused by the contact between blood and artificial materials, the internal environment of the organism can be altered, which in turn affects the function of the organs. 1, metabolic changes Stronger stress and flat-flow perfusion patterns during extracorporeal circulation are likely to cause mild metabolic acidosis and hyperglycemia. 2.Water and electrolytes Due to the temperature change and stopping fluid perfusion, the blood potassium concentration changes greatly, and both high and low potassium are more common. 3, blood changes When the extracorporeal circulation time is short, there is little damage to the blood system, but when the extracorporeal circulation time is too long and the amount of intracardiac suction is large, the blood destruction is more obvious. This is manifested by the destruction of red blood cells, the increase of free hemoglobin, the disorder of coagulation mechanism caused by the decrease of various coagulation factors and platelets, and the appearance of blood leakage after stopping extracorporeal circulation. 4, affect the function of organs Due to the change of blood flow pattern and the production of inflammatory mediators during extracorporeal circulation, the function of organs is affected to a certain extent. With the development of extracorporeal circulation management techniques and artificial materials, organ hypofunction directly caused by extracorporeal circulation is rare, except for organs with preoperative lesion base that may appear hypofunction.