Shock is usually divided into early shock, shock phase, and late shock phase. In the early stage of shock, the microcirculation is characterized by spasmodic contraction of the microarteria, posterior microarteria, and anterior sphincter of capillaries, which leads to the closure of a large number of capillaries and contraction of microvenules, and the microcirculation is in a state of ischemia, resulting in cellular metabolic disorders. In the middle of the shock period, the small blood vessels of the whole body will be continuously constricted, and the microcirculation will be continuously ischemic and hypoxic, which will slowly develop into the vasodilation and stasis of the whole microcirculation, and the amount of cardiac blood return will be obviously reduced, which will show that the resistance of peripheral blood vessels will be reduced, and the arterial blood pressure will be obviously decreased. If the shock is not corrected and the shock is advanced, there will be extensive intravascular coagulation and systemic multi-organ failure, manifested by extensive microvascular obstruction, secondary fibrinolysis and bleeding, as well as intra-microvascular hemolysis, etc., which will further reduce the amount of cardiac blood return and blood pressure will drop continuously.