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An excess of blood within an organ or tissue caused by blood vessel dilation or impaired drainage, especially of the skin.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



also plethora, an excess of blood in a tissue or organ. One may distinguish arterial and venous hyperemia. Arterial (active) hyperemia arises as a result of increased blood flow in the arteries owing to increased tonus of the vasodilator nerves or decreased tonus of the vasoconstrictor nerves. Among its causes are increased sensitivity of the blood vessels to physiological stimuli or the influence of extraordinary stimuli (such as bacterial toxins, high temperature, and products of tissue decomposition); in humans psychogenic factors (such as shame and anger) play a large role. Arterial hyperemia is characterized by dilatation of the arteries in the hyperemized area, elevation of temperature in the area, acceleration of blood flow, and reddening (for example, hyperemia of the face). It is accompanied by intensification of metabolic processes in the tissues and promotes the regeneration of tissues. Hemorrhages may occur during arterial hyperemia if there are pathological changes in the blood vessels. Arterial hyperemia is induced for therapeutic purposes by means of mustard plasters and cupping glasses. Venous (passive, static) hyperemia occurs when the outflow of blood along the veins is obstructed as a result of pressure on the venous wall (cicatrix, tumor, varicose dilatation of the veins, or edema), while the inflow remains unchanged or when there is a weakening of cardiac activity. Venous hyperemia is characterized by deceleration of blood flow to the point of complete stasis. Oxygen deficit develops in the tissues, the vascular walls become more permeable, and edema develops. Prolonged blood stasis and edema may lead to atrophy of the parenchyma of an organ.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Excitement phase; drastic reduction of spiracle beats; hyperemia of fins present, but less intensely than at other concentrations.
All patients had conjunctival hyperemia followed by limbal infiltrate and trantas dots (83.87%) each.
In group administered with AST and I/R, hyperemia, hemorrhage, edema, inflammatory cell infiltration and partial enlargement in inter alveolar septum were observed (Figure 3E).
Secondary clinical outcome measures included synovial thickness by USG, hyperemia by Power Doppler, ROM, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Short Form 36 (SF-36).
The effect on conjunctival hyperemia and papillary hypertrophy was significant.
baumannii 20 Hyperemia P aeruginosa 30 Secretion Negative 31 Hyperemia Negative 33 Hyperemia Negative 68 Hyperemia A.
No hyperemia or conjunctivitis was observed in the present case, while a mild itching was present.
Bulbar and Limbal Hyperemia. Increased conjunctival redness is often one of the first signs indicating abnormal strain or pathological changes in the eye.
It means that functioning of endothelial cells significantly affects the hyperemia response in the finger.
On the following day, the patient noticed a sudden visual acuity (VA) decline and hyperemia in the right eye.
Bilateral auricular chondritis was present, with moderate hyperemia of the right ear (Figure 2).
FMD and reactive hyperemia (the transient increase in blood flow that occurs following a brief period of arterial occlusion) of an obese adult male with chronic motor complete paraplegia.