BRAIN DEATH

A widely shared conviction is that organisms are alive when their organs function in an integrated way; and that, consequently, death occurs when this somatic unity is lost. In most cases, this point is reached after heartbeat and breathing have stopped and have failed to resume spontaneously. For hundreds of years, this cardiopulmonary criterion had been the standard for determining death, until in the middle of the twentieth century three developments in intensive-care medicine called it into question: the advent of positive pressure ventilation, the promotion of cardiopulmonary resuscitation, and the first successful heart transplantation. What had previously been deemed permanent, suddenly became reversible.

In 1968, an ad hoc committee of the Harvard Medical School ultimately argued that the cardiopulmonary criterion was no longer applicable under these circumstances and suggested that neurological criteria be used instead. This proposal proved to be very influential, and most legal systems around the world adopted brain death as the new standard.

Identifying the destruction of a single organ with the death of the organism as a whole requires an exceptionally well-founded justification. I investigated if such a justification can be given in the case of the brain. I compared brain death with conditions that are universally accepted as constituting living organisms – the persistent vegetative state and anencephaly – to show that cognitive capacities are not essential to organismic functioning and that, hence, only brainstem-mediated functions can be relevant to biological definitions of death. With cognitive capacities excluded, five major differences remain between a brain-dead body and a body in a persistent vegetative state, whose respective significance to integrated functioning I evaluated by contrasting them with high cervical spine transection, locked-in syndrome, bilateral vagotomy, and panhypopituitarism. I concluded that the dissimilarities between bodies in these conditions and brain-dead bodies on life support do not warrant considering the former alive but the latter dead.

I then took these physiological considerations to a more abstract level by introducing a classification of the different ways in which vital functions can cease to be performed. This enables one to see why it is highly problematic to base one’s judgement of whether a biological entity is dead or alive on the status of the neurological control mechanism of a function, rather than on the execution of the task itself: the growing sophistication of life-support systems has given rise to a dangerous decoupling of the performance of a function from the retention of neurological control over it.

Provided that the level of internal coordination between the different organs is still high enough to account for a sufficient degree of somatic unity, the existence of an organism is not conditional on the means by which a certain vital function is directed, but rather on its being performed or having ceased. In intensive-care settings, the status of the brain does therefore not reliably indicate whether an organism is dead or alive since the former need not correspond to the functions that are being carried out in the body – a discrepancy that can yield false positives. I thus concluded that, for these reasons, the brain is not a suitable locus for determining the death of an organism in the presence of extensive life support. Fifty years after its introduction, the neurological criterion is now facing the same fate as its cardiopulmonary predecessor.

Associated Publication:

Meier, L. J. (2022): The Demise of Brain Death. The British Journal for the Philosophy of Science 73 (2): 487-508. DOI: 10.1093/bjps/axz045.