Tuesday, February 05, 2008
Hemodynamics - Thrombosis, Embolism, Shock
A thrombus is a stationary mass of blood elements that remains attached to its place of origin along the wall of a blood vessel.
Thrombi are not clots although they are partially made up of clotted blood. Unlike most clots, a thrombus is always the result of a pathologic event. Clots are normal (usually) and occur outside a blood vessel.
The formation of a thrombus is not initially dependent on the clotting process. Thombi begin endothelial injury and an initial platelet clump. Layers of platelets are added followed by the adherence of white blood cells. A clot then adds volume as the thrombus grows.
You can find a full text article concerning deep vein thrombosis here and another full text article here.
An embolus is an intravascular object (air, tumor fragment, broken off thrombus, calcium fragments) that circulates in the bloodstream until it becomes lodged in a vessel obstructing the blood flow.
Ischemia is a lack of oxygen supply to a tissue usually due to obstruction of blood flow.
Lack of oxygen supply to a tissue can result in a tissue death called an infarct
See photos of an infarct of the heart here.
Shock is a state of systemic low blood flow. It can occur due to a loss of blood or because cardiac output is reduced.
Cardiogenic shock occurs when the heart is incapable of maintaining blood pressure. You can read much more about cardiogenic shock here.
Hypovolemic shock is a result of an underfilled vascular space, usually the result of hemorrhage. It can also be caused by fluid loss in cases of severe burns or diarrhea. Read more about hypovolemic shock here.
Septic shock is associated with systemic bacterial infections (sepsis) usually gram-negative bacterial infections. It is due to a massive inflammatory response to the infection. Read more about septic shock here.