Of course, an old philosopher was right when he said that the whole universe is moving and the life is motion. But there is one exclusion in pathology, stasis. Stasis is complete stop of blood flow within blood vessels. Stasis is typical pathological process. It is a result, a close consequence of other typical pathological disorders of microcirculation. The progressive slowing of blood flow may result either from advanced venous hyperemia and venous congestion, or it may result from progressing ischemia. Moving force is a pressure difference between arteriole and venule. In progressive venous congestion, the venous pressure gets higher and higher and higher, and finally, it equalizes with in-flow arterial pressure, and blood stops, or vice versa in advanced ischemia with constant venous pressure or even diminished venous pressure. Arterial pressure gets down and down, and finally, equalizes with the pressure on venous and no difference, no motion. Blood also stops. So, there are two kinds of hemodynamic stasis. Congestive stasis after venous hyperemia, and ischemic stasis after ischemia. And as you can see in this picture, they start differently, but finally, they come to the same complete stop of blood within blood vessels. The third, very important variant of stasis is so-called true stasis or capillary stasis. It is a kind of stasis caused by changes within capillaries, changes of rheological properties of blood itself, without primary ischemic or congestive disorders. So, blood pressure is still higher in arterial portion of microcirculation. It is still lower in venous portion, but within capillaries, something happened which created an obstacle for moving blood. It can be thrombi, it can be margination of leukocytes, it can be fibrin formation, or it can be sludge of erythrocytes, or all that resumes together. So, venous stasis, ischemic stasis, and true capillary stasis, which probably is most important. Sometimes, stasis may be brought by several different pathogenetic mechanisms combined, acting together, and we shall call it combined stasis. For example, in a circulatory shock after severe blood loss, person has ischemia, but also, there are changes of rheological properties of blood in capillary bed. There is intravascular coagulation and the pathogenesis of stasis in shock is not so simple. It combines ischemic mechanism and true capillary mechanism. Stasis always is precedent in dynamic by prestatic phenomena. Among them, phenomena already known to you from previous parts of our lectures. These are jerky blood motion, and pendulum-like blood motion. As a rule, before complete stasis, you can observe either a pendulum-like or jerky irregular motions of blood. Another very important prestatic phenomena is formation of so-called rouleaux. Rouleaux is French term. It is a column of coins. And as you can see in this picture, in very slow blood flow in change of rheological properties of blood, blood cell elements may stick together and produce slowly moving cylinders called rouleaux, that is prestatic phenomenon. Another prestatic phenomenon is sludge, sludge of erythrocytes. You can no longer observe the intracellular borders between separate erythrocytes in blood. They confluence, they form sludge. You can see these in visual picture, in visual microscopy, and in electronogram as well. Stasis is a very important outcome of typical disorders of microcirculation. Here, you can see the major characteristic of microcirculation in circulatory shock, severe syndrome of multiorgan hypoxia and multiorgan failure. You can see that initially, in so-called compensated phase of shock, we have centralization of blood flow and ischemia produced in many peripheral organs to spare the resources of blood for heart and brain. But because ischemic stasis will occur after some time, there will be second phase of decentralization of the blood flow and formation of different obstacles for normal organ perfusion: thrombi, fibrin, sludge, platelet adhesion, and so on. All these taken together produces disseminated intravascular coagulation in microcirculatory bed of many ischemic organs in shock. And in spite of open arteriole and decentralization of blood flow, normal perfusion is no longer possible because blood does not flow normally anymore. Its normal flow is disturbed by that prestatic phenomena. That's why the stasis is a key element in the pathogenesis of circulatory shock. One of the pioneers in studies of stasis was a famous Soviet polymath, Leonardo of 20th century, Alexander Leonidovich Chizhevsky. He is world famous for his discovery of heliobiological phenomena and relation between cyclic solar activity and social and biosocial processes on the Earth. But it is less know, but it is also true that he was one of the first who biophysically explored the electrical and the physical properties of flowing blood in microcirculatory vessels, and the well known phenomenon of erythrocyte sedimentation rate, which is now measured in every outpatient department in very many patients. The biophysical basis for that dates back to classical works by Alexander Chizhevsky. That's probably enough for today. We have resumed our lecture in typical pathological processes involving microcirculation.
