Diagnosing brain death

Abstract

Throughout mankind's history, the concept of death has changed constantly in parallel with the scientific, cultural and social evolution of the various eras. Until the nineteenfifties, the interruption of the heart beat or breathing marked the point in time in which an individual was deemed to be dead. With the introduction and dissemination of resuscitation techniques as well as with the availability of total artificial respiratory and cardiocirculatory support, it is no longer sensible to equate the time of death with the time of cardiorespiratory arrest. In fact, externally controlled respiratory and cardiocirculatory techniques have made it possible to consider that a patient who is no longer able to breath autonomously is nevertheless alive. However, these cardiopulmonary resuscitation techniques may also allow a patient to continue to be well oxygenated and maintain sufficient haemodynamic stability for limited periods even when all cerebral functions have been completely and irreversibly lost. It therefore follows that the confirmation of death cannot be based on the observation or conservation of autonomous cardiopulmonary activity alone. Over the past thirty years this observation has led to the introduction of the concept of "brain death", intended as a definitive and complete loss of all functions of the CNS. In the 1960's the French school of medicine proposed the term coma depassée to describe this condition, however from a semantic point of view the term is inaccurate because, as it indicates a state of brain death, it is no longer possible to speak of coma. Coma in fact implies that brain activity is still present, albeit compromised to a greater or lesser extent. It is therefore preferable to avoid such expressions as "irreversible coma" but instead use the term "brain death" (BD) to indicate a subject whose cerebrum is no longer vital but whose cardiopulmonary function is still present. By BD, we therefore signify the irreversible arrest of all brain function, including that of the brainstem, which is precisely the structure whose loss of function is required for the verification of brain death (14). © 2006 Springer Berlin Heidelberg.