The shock is triggered by the critical drop in circulating blood volume massive loss of red blood cells intensifies the tissue hypoxia. Clinically the most significant cause of hemorrhagic shock is acute bleeding from an isolated injury to a large blood vessel, gastrointestinal bleeding, nontraumatic vascular rupture (e.g., aortic aneurysm), obstetric hemorrhage (e.g., uterine atony), and hemorrhage in the region of the ear, nose, and throat (vascular erosion).

However, differences exist between the two subcategories in terms of the extent of soft tissue damage. The characteristic feature of both, hemorrhagic and traumatic hemorrhagic shock is bleeding. Hypovolemic shock is a condition of inadequate organ perfusion caused by loss of intravascular volume, usually acute. In obstructive shock, hypoperfusion due to elevated resistance shall be treated with an immediate life-saving intervention.

Cardiogenic shock is due to inadequate function of the heart, which shall be treated, depending on the situation, with drugs, surgery, or other interventional procedures. Distributive shock, on the other hand, is a state of relative hypovolemia resulting from pathological redistribution of the absolute intravascular volume and is treated with a combination of vasoconstrictors and fluid replacement. Hypovolemic shock is due to intravascular volume loss and is treated by fluid replacement with balanced crystalloids.

Hypovolemic shock relates to the blood and fluids compartment while distributive shock relates to the vascular system cardiogenic shock arises from primary cardiac dysfunction and obstructive shock arises from a blockage of the circulation.

There are only four major categories of shock, each of which is mainly related to one of four organ systems.

System shock 2018 release