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Cerebral hypoxia is typically grouped into four categories depending on the severity and location of the brain's oxygen deprivation: [20] Aneurysm in a cerebral artery, one cause of hypoxic anoxic injury (HAI). Diffuse cerebral hypoxia – A mild to moderate impairment of brain function due to low oxygen levels in the blood.
Hypoxia can be due to external causes, when the breathing gas is hypoxic, or internal causes, such as reduced effectiveness of gas transfer in the lungs, reduced capacity of the blood to carry oxygen, compromised general or local perfusion, or inability of the affected tissues to extract oxygen from, or metabolically process, an adequate supply ...
Hypoxemia is usually defined in terms of reduced partial pressure of oxygen (mm Hg) in arterial blood, but also in terms of reduced content of oxygen (ml oxygen per dl blood) or percentage saturation of hemoglobin (the oxygen-binding protein within red blood cells) with oxygen, which is either found singly or in combination. [2] [5]
Brain ischemia is a condition in which there is insufficient bloodflow to the brain to meet metabolic demand. [1] This leads to poor oxygen supply or cerebral hypoxia and thus leads to the death of brain tissue or cerebral infarction/ischemic stroke. [2] It is a sub-type of stroke along with subarachnoid hemorrhage and intracerebral hemorrhage. [3]
The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal arterial blood oxygen saturation levels in humans are 96–100 percent. [1] If the level is below 90 percent, it is considered low and called hypoxemia. [2] Arterial blood oxygen levels below 80 percent may compromise organ function, such as ...
Unconsciousness may occur as the result of traumatic brain injury, brain hypoxia (inadequate oxygen, possibly due to a brain infarction or cardiac arrest), severe intoxication with drugs that depress the activity of the central nervous system (e.g., alcohol and other hypnotic or sedative drugs), severe fatigue, pain, anaesthesia, and other causes.
Brain death refers to an irreversible total loss of brain function. [200] [201] This is characterised by coma, loss of reflexes, and apnoea, [200] however, the declaration of brain death varies geographically and is not always accepted. [201] In some countries there is also a defined syndrome of brainstem death. [202]
A decrease in circulation in the brain vasculature due to stroke or injury can lead to a condition known as ischemia. In general, decrease in blood flow to the brain can be a result of thrombosis causing a partial or full blockage of blood vessels, hypotension in systemic circulation (and consequently the brain), or cardiac arrest. This ...