Ischemia

Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body. A shortage of blood supply at any site causes a shortage of oxygen (hypoxia) available for cellular metabolism, (i.e., needed to keep tissue alive). Typically, ischemia is caused by problems with blood vessels and the resultant damage to or dysfunction of tissue—e.g., general hypoxia and microvascular dysfunction. It also implies local hypoxia in a part of a body resulting from constriction (such as vasoconstriction, thrombosis, or embolism). Ischemia causes not only insufficiency of oxygen but also reduced availability of nutrients and inadequate removal of metabolic wastes. Ischemia can be partial blockage (poor perfusion) or total blockage. The inadequate delivery of oxygenated blood to the organs must be resolved either by treating the cause of the inadequate delivery or reducing the oxygen demand of the system that needs it. For example, patients with myocardial ischemia have a decreased blood flow to the heart and are prescribed with medications that reduce chronotropic and inotropic effect to meet the new level of blood delivery supplied by the stenosed vasculature so that it is adequate.