What is death? (when the brain can be considered dead)

What is involved in the dying process?

Cells die as they are deprived of oxygen. Some cells can live without oxygen longer than others. Clinical death occurs when the heart stops beating. At this point, it is possible to reverse death through cardiopulmonary resuscitation, ventilators or transfusions. Blood is no longer carrying enough oxygen through the body for other cells to survive. A few minutes after the heart stops, unless there is an intervention, biological death occurs. Biological death happens when the brain is deprived of oxygen for four to six minutes; the brain cells then die. At this point, there is no possibility of reversing death.

When can a person be declared dead?

Death occurs when brain activity ceases. This is based on a definition created by Harvard Medical School in 1968. Doctors there believed that irreversible brain damage or brain death was a clear indicator that the patient was dead. While Harvard’s definition can be loosely interpreted as death of the cortical brain, most countries have laws stating that the entire brain must be dead, including the brain stem. Because the brain stem regulates movement, speech and respiration, including the brain stem in the definition of death assumes that other bodily functions have ceased.

What causes brain death?

Brain death is caused by injury to the brain. Natural causes as well as traumatic injuries have the same effect. Any injury that causes the brain to bleed, swell or do both can lead to brain death.
Traumatic injuries can be open (a wound) or closed (a blunt force) and are capable of causing brain death. Anoxia or lack of oxygen to the brain can bring about brain death. Anoxia occurs when the brain is injured due to an inability of the lungs to produce oxygen for the brain to use. Smoke inhalation and drowning are two possible causes. Drug overdoses may also deplete oxygen and cause brain death.
Natural causes can include a bacterial, viral or fungal infection, a ruptured aneurysm, or a stroke. Tumors can also prevent blood flow to the brain, depriving it of oxygen and resulting in brain death.

What is death? (when the brain can be considered dead)