ischemia is a medical term that means deficiency or absence of blood supply and, consequently, of oxygen, in a certain tissue or organ.
The word "ischemia" comes from the Greek "we arecha", Where iskho = retain and haima = blood.
When the blood supply is less than the basic need for the organ or tissue in question, ischemia sets in.
Ischemia may be due to causes functional (hemorrhage, severe hypotension, vascular spasm) or mechanics (vascular obstruction/compression, decreased vascular lumen).
The intensity and severity of ischemia depends on the degree of vascular obstruction (total or partial), it can occur quickly, in the case of a thrombus, for example, or slowly, as in atherosclerosis.
If ischemia is prolonged, it can cause necrosis tissue (death), as in the acute myocardial infarction.
THE cerebral ischemia or Ischemic cerebrovascular accident (Ischemic Stroke), popularly known as "stroke", is the lack of blood supply in a certain area of the brain due to the obstruction of an artery.
The main causes of ischemia they are:
- Obstruction of vascular lumen:
- Anatomical obstruction: tumor compression, hematoma, decubitus, arterial wall thickening (atherosclerosis), thrombi, clots;
- Vascular spasms.
- Decrease in pressure between arteries and veins:
- States of shock due to reduced blood pressure;
- Reduced blood flow in capillaries.
- Increased blood viscosity: Reduces flow especially in microcirculation;
- Increased demand: In isolation, it usually does not cause ischemia, becoming important when associated with other causes.