Hemorrhage (the accumulation of blood that has escaped from)

HEMORRHAGE, the accumulation of blood that has escaped from blood vessels, in the body cavities or in the tissues. Cavity hemorrhages are designated according to the name of the cavity containing the escaped blood (see Haemothorax, Haemopericard, Haematometra, Haematosalpinx, Haematocele, Haematomyelia and others). Hemorrhages into tissues give various names depending on their external appearance and size (ecchymoses, suggilatio, suffusio, vibices, petechiae, purpura and others). Significant accumulations of blood, surrounded by dense tissues such as a capsule, are called blood tumors-hematomas (see). Diffuse impregnation of tissues with erythrocytes is called hemorrhagic infiltration or hemorrhagic infarction. Blood that has exited the vessel into tissues collects in the intertissue spaces and its pressure helps to stop the bleeding. Blood that has escaped into tissues soon undergoes coagulation; if before that, during slow bleeding, the different components of blood (platelets, erythrocytes, leukocytes) have time to separate from each other, pictures are obtained that resemble thrombi ("extravascular thrombosis", according to Ribbert). Blood that has escaped into serous cavities, as was previously thought, may not coagulate for a very long time; however, it has now been established (Henschen, Herzfeld, Klinger, Israel) that it generally loses the ability to coagulate, as it undergoes defibrination. The latter is facilitated in the pericardial cavity by the movements of the heart, in the pleural cavity by the movements of the lungs, and in the peritoneal cavity by the movements of the intestines. Some significance in this may also have the properties of the mesothelium of the serous cavities. Following the coagulation of blood that has escaped into tissues, changes occur in the erythrocytes: some of them swell, some wrinkle; their hemoglobin sometimes first condenses into grains, then is leached out and impregnates the surrounding tissue, being adsorbed on fibrous structures and in cells (especially in macrophages). Subsequently, part of the hemoglobin is resorbed, but most of it is converted into an iron-containing granular amorphous pigment of brownish-yellow color-hemosiderin (see) and into an iron-free red crystalline pigment-hemoidin, identical with bilirubin. The formation of hemosiderin occurs only under the influence of the vital activity of cells (Neumann, Lubarsch), therefore it always accumulates at the border of the hematoma with normal tissue; in the deep parts of the hematoma only hemoidin is present, which is formed without the participation of cells. The presence of hemosiderin in tissue can be established using the iron reaction already 2-3 days after bleeding. The larger part of the pigment usually lies in macrophages (siderophages) of connective tissue. At the site of hemorrhage in tissues, a normal inflammatory reaction occurs, during which the escaped blood and the pigments formed from it undergo resorption. However, hemosiderin sometimes remains lying for a very long time at the site of the former hemorrhage, causing pigmentation of scars (e.g. in the brain). The presence of hemosiderin is therefore a sure sign of a former hemorrhage. More extensive hemorrhages undergo organization, growing into connective tissue. Outcomes of hemorrhage may be suppuration, necrosis, calcification. In addition to the pigments mentioned above, during the breakdown of erythrocytes in hemorrhage, a certain amount of granular fat-containing pigment-lipofuscin is formed; however, the most characteristic pigment encountered in hemorrhage is only hemosiderin. Part of the erythrocytes that have entered the tissue during bleeding are carried away unchanged and enter the regional lymph nodes, where they are destroyed in the cells of the reticulo-endothelium. Here, large amounts of hemosiderin granules formed in place and carried further by the lymph flow also accumulate. Blood that has escaped into serous cavities undergoes hemolysis very slowly (a day after bleeding), which is of great importance, as such blood can be successfully used for reinfusion (Filatov). The local effect of hemorrhage on tissue can vary depending on the size of the hemorrhage and the nature of the tissue in which it occurred. Significant hemorrhages in such tissues as muscles, adipose tissue, push the tissues apart and only compress them, just like hemorrhages into a cavity; on the other hand, hemorrhages can destroy tissue both in the sense of complete destruction of tissue at the site of hemorrhage (e.g. in hemorrhage into brain tissue), and in the sense of dissociation of tissue elements with subsequent degenerative changes or necrosis of dissociated elements (for example, hemorrhage into heart muscle, into nerves, into parenchymal organs). Finally, hemorrhages can disrupt the vital activity of tissue in the sense of weakening its resistance to various normal influences; this includes digestion and formation of erosions in the gastric mucosa with hemorrhages in it; formation of ulcers in places of hemorrhages into the intestinal mucosa. - On the moments causing hemorrhage and on the general significance of hemorrhage-see Bleeding.

H. Anichkov