How Long Can the Brain Survive Without Oxygen?
Lack of oxygen in the brain will cause permanent brain damage in as little as four minutes. Another four to six minutes without the brain receiving blood will result in increased brain damage, coma and then death. In order to reduce the chances of permanent or anoxic brain damage in a person who is unconscious, CPR should be performed until their breathing and heartbeat return or until qualified medical help arrives.
The primary causes that result in an adult not breathing or having a heartbeat are accidents and injuries, excessive bleeding, infection in the bloodstream, near-drowning, drug overdose and abnormal hearth rhythms, and heart attacks that are associated with heart disease. Health issues or accidents such as choking, suffocation, drug use, carbon monoxide poisoning from malfunctioning gas appliances, electrical shock and heart arrhythmia can increase the chances of losing consciousness, which can result in anoxic brain damage.
If a person receives mild to moderate hypoxic brain damage from experiencing any of these conditions and is resuscitated, they may end up suffering from symptoms such as seizures, confusion, headaches, decreased attention span and concentration, poor coordination, occasional loss of consciousness and personality changes or mood swings.
Evidence of brain damage in individuals is detected by running tests such as MRIs, Head CT scans and SPECT scans. Symptoms associated with decreased brain function do not always show up right away and may not appear until several days or weeks after the experience occurred.