Advances in medicine, surgery, and public health have gradually increased the average life expectancy of the population. At the same time, patients with chronic diseases experience increased survival periods in relatively good health, leading to advanced single or only few organ failures, making them adequate candidates for organ replacement via transplantation. The accumulated knowledge and technological progress made up to the late 1950s in critical care medicine allowed physicians to artificially maintain body oxygenation and blood perfusion regardless of brain function. Simultaneously, the highly successful developments in the field of organ transplantation promoted an ever increasing demand and need for such organs.
The first solid organs (e.g., liver, kidney) for transplantation were obtained from donors in whom cardiac and pulmonary function had ceased, otherwise referred to as cadaveric organ donors. It was soon learned that the continued cardiopulmonary function of the brain-dead donor provided healthier, blood perfused organs. This promoted deep changes, and with it controversies in the medical, ethical, and philosophical perspectives about death. Through scientific landmark achievements, medicine empowered the dead to help the living through the wonder of organ donation.
The first set of brain death criteria were the Harvard Brain Death Committee Criteria from 1968. These, with few changes induced by newer medical development, remain the backbone for the diagnosis of brain death. In 1981, the United States Uniform Determination of Death Act established that death can occur by one of two clinical events: cessation of cardiopulmonary function or cessation of function of the entire brain. Brain death is an artificial, technologically driven, clinical condition of oxygenation of a cadaver.
For the diagnosis of brain death, clinical evidence of severe, extensive, and irreversible brain injury (metabolic or anatomic) needs to be present. Confounding factors or diagnoses that can mimic brain death need to be carefully ruled out, such as severe hypothermia or chemically induced skeletal muscle paralysis.
In the appropriate context, three clinical elements are present: coma (cessation of function of either the upper brain stem or both cerebral hemispheres), loss of reflexes from the brain stem, and inability to spontaneously breath (lower brain stem) even when a maximal respiratory challenge is provided (the apnea test).
The so-called “confirmatory” tests are only used when most of the elements for the diagnosis of brain death are present, but it is not possible to reliably satisfy all of the criteria on clinical grounds. For example, in patients with severe facial injuries or in those with advanced pulmonary disease and chronic carbon dioxide retention. These tests are classified in two subgroups: blood flow studies, such as transcranial Doppler (ultrasound), or electrical tests, such as electroencephalography. These “confirmatory” tests cannot take the place of the clinical criteria.
The diagnosis of brain death is serious and irreversible. It confirms that the person is dead. When the diagnosis is reached, the person becomes a cadaver. If the option of organ donation is not viable, all artificial means of sustaining body oxygenation and blood circulation should be discontinued.
Brain death is a difficult diagnosis for families to understand and for physicians to communicate.
- American Academy of Neurology, http://www.aan.com/public/indecfm
- American Academy of Neurology. (1995). Practice parameters for determining brain death in adults (summary statement). The Quality Standards Subcommittee of the American Academy of Neurology. Neurology, 45(5), 1012–1014.
- American Academy of (1987). Report of special Task Force. Guidelines for the determination of brain death in children. American Academy of Pediatrics Task Force on Brain Death in Children. Pediatrics, 80(2), 298–300.