Brain death is caused by severe brain trauma, massive brain hemorrhage, massive cerebral infarction, cardiac arrest, drowning, severe asphyxia and other fatal diseases that cause severe damage to the brain structure and loss of all brain functions. The brain structure of a brain-dead patient is completely destroyed, the patient is in a deep coma, and there is a complete loss of consciousness and no sensation. In general, the diagnosis of brain death is equivalent to pronouncing a person’s death.