The neurological damage that results from depriving the brain of oxygen or blood, or both, for several minutes. The damage may range from a transient loss of short-term memory to persistent vegetative coma. Many conditions can result in an oxygen deficiency in the brain, which is acutely dependent on oxygen, blood, and glucose to work normally. These conditions include carbon monoxide inhalation, cardiac arrest, hypotensive episodes of any kind (e.g., any form of shock), near drowning, and suffocation. If patients are not rapidly revived and oxygenation restored, the hippocampus, and later the other cerebral structures, may be permanently injured and the patient may suffer irreversible brain damage.