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Brain ischemia is insufficient blood flow to the brain, and can be acute or chronic. Acute ischemic stroke is a neurological emergency typically caused by a blood clot blocking blood flow in a vessel in the brain. [15] Chronic ischemia of the brain may result in a form of dementia called vascular dementia. [16]
Ischemia, meaning insufficient blood flow to a tissue, can also result in hypoxia in the affected tissues. This is called 'ischemic hypoxia'. Ischemia can be caused by an embolism, a heart attack that decreases overall blood flow, trauma to a tissue that results in damage reducing perfusion, and a variety of other causes.
Brain ischemia has been linked to a variety of diseases or abnormalities. Individuals with sickle cell anemia, compressed blood vessels, ventricular tachycardia, plaque buildup in the arteries, blood clots, extremely low blood pressure as a result of heart attack, and congenital heart defects have a higher predisposition to brain ischemia in comparison to the average population.
Stroke is a medical condition in which poor blood flow to a part of the brain causes cell death. [5] There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. [5] Both cause parts of the brain to stop functioning properly. [5]
Coronary ischemia, myocardial ischemia, [1] or cardiac ischemia, [2] is a medical term for abnormally reduced blood flow in the coronary circulation through the coronary arteries. [3] Coronary ischemia is linked to heart disease, and heart attacks. [4] Coronary arteries deliver oxygen-rich blood to the heart muscle. [5]
Blood flow may increase up to twice the normal flow but no more. If the increased blood flow is sufficient to supply the brain's oxygen needs then no symptoms will result. [6] However, if blood flow cannot be increased or if doubled blood flow does not correct the problem, symptoms of cerebral hypoxia will begin to appear.
Shock is a medical emergency and requires urgent medical care. If shock is suspected, emergency help should be called immediately. While waiting for medical care, the individual should be, if safe, laid down (except in cases of suspected head or back injuries). The legs should be raised if possible, and the person should be kept warm.
Tissue hypoxia refers to low levels of oxygen in the tissues of the body and the term hypoxia is a general term for low levels of oxygen. [2] Hypoxemia is usually caused by pulmonary disease whereas tissue oxygenation requires additionally adequate circulation of blood and perfusion of tissue to meet metabolic demands. [4]