Brain death is defined by permanent loss of all brain function.
Brain death can occur following traumatic brain injury, stroke or following a cardiac or respiratory arrest during which oxygen supply to the brain is interrupted for a prolonged period.
Well-defined protocols are followed during the care of a patient suspected of brain death. Patients with brain death are usually very unstable with respect to blood pressure, kidney function and heart rate. The main reason to continue care of a patient with brain death is for the consideration of organ donation.
Declaration of death occurs by one of two major methods. The first, and most common method, is documentation of permanent loss of spontaneous heart and respiratory function. This means that the heart has permanently stopped beating and the patient has permanently stopped breathing. The second method is documentation of brain death. Regardless of the method used, legal pronouncement of death is the doctor's responsibility. The total brain is made up of the large rounded portion of the brain, the cerebral cortex, and the stalk below the cortex, the brain stem. Irreversible and permanent loss of all brain function means that both the cerebral cortex and the brain stem have died and will never recover. Well-defined testing protocols are followed during documentation of brain death. The doctor performs most of these tests at the bedside. Sometimes additional tests such as an electroencephalogram (EEG) or a brain blood flow study are necessary.
Related LinksNational Library of Medicine
The National Library of Medicine presents information and pictures about brain death.