12.1. Causes of ischemic injury
Ischemic injury is a type of closed injury. The extent of ischemia may differ, the lesion affecting the whole body or single vital organs (brain, heart, kidneys) or may be local when non-vital organs (e.g., limbs) are affected. at the same time, even local hypoxia can also cause both local and general complications. Local complications (necrosis) lead to local dysfunction. General complications are associated with cytolysis, release of toxic products into the body from the ischemia focus (ischemic toxicosis), which can pose a direct threat to life.
Depending on the causes of tissue hypoxia, circulatory failure may be classified as relative or absolute.
Relative circulatory failure is caused by increased functional stress when normal blood flow is insufficient to meet the significantly increasing needs of tissues (upon long-term running or racewalking, as well as other types of hours-long considerable physical effort).
Absolute circulatory failure is divided into general caused by cessation of systemic blood flow due to clinical death, as well as its significant disorder associated with decompensated shock or general hypothermia, and local.
The following are causes of local circulatory failure:
► compression by external forces, when the whole mass of tissues is pressed by an external object (under rubble of collapsed buildings, inappropriately applied plaster cast), or from within due to severe edema (compartment syndrome, tunnel syndrome);
► tourniquet ligating great vessels that supply blood to this particular area;
► lesion of a great vessel;
► embolism, when the lumen of a great vessel is blocked from within;
► traumatic avulsion of the limb with its subsequent replantation;