A ischemia [ ɪsçɛmiː ] (derived from ancient Greek ἴσχειν / ἔχειν is-chein / echein , German , restrain ' and αἷμα haima , German , blood' ) is an often with pain associated hypoperfusion or a complete circulation failure of a tissue , a body part or organ , which can lead to a malfunction.
The narrowing is called stenosis , for example in atherosclerosis and arterial occlusive disease (AVK) . Functional constrictions can also occur, for example in Raynaud's syndrome or as a physiological reaction in circulatory shock .
Occurrence and consequences
Ischemia can occur temporarily ("passager", transient) and have no consequences for the insufficiently supplied tissue. If the ischemia lasts longer than tolerated by the tissue or if the insufficient supply is so severe that permanent tissue damage threatens, the condition is called critical ischemia .
The cellular metabolism is hindered or prevented by ischemia . The ischemia caused by the restriction or interruption of blood flow is associated with a lack of oxygen in the affected area. If nerve tissue is undersupplied for a longer period of time, a cascade occurs in which high intracellular calcium concentrations contribute to the uncontrolled release of the neurotransmitter glutamate and thus ultimately damage surrounding cells of the tissue in an excitotoxic manner . These processes can lead to the death of cells ( necrosis ) and thus to an infarction , e.g. B. in ischemic heart disease, in which part of the heart muscle is not supplied with sufficient blood , lead to a heart attack . Pressure-related ischemia with tissue damage leads to pressure ulcers ( pressure ulcers).
The period of time tolerated without permanent tissue damage ( ischemia time ) differs from organ to organ. For the brain it takes a few minutes, for many organs that can be transplanted such as the heart or kidneys, depending on the cooling and nutrient solution, a few hours and for extremities sometimes over twelve hours.
- Wolfgang Schwerd: suffocation (lack of oxygen). In: Wolfgang Schwerd (Hrsg.): Brief textbook of forensic medicine for doctors and lawyers. 3rd, revised and expanded edition. Deutscher Ärzte-Verlag, Cologne-Lövenich 1979, ISBN 3-7691-0050-6 , pp. 71–84, here: pp. 71–73.
- Alphabetical index for the ICD-10-WHO version 2019, volume 3. German Institute for Medical Documentation and Information (DIMDI), Cologne, 2019, p. 431
- Peter C. Heinrich, Matthias Müller, Lutz Graeve (Eds.): Löffler / Petrides: Biochemistry and Pathobiochemistry . 9th edition. Springer, Berlin / Heidelberg 2014, ISBN 978-3-642-17972-3 , pp. 977 .
- Guideline microsurgical replantation of severed body parts ( Memento from August 19, 2007 in the Internet Archive ).