Cryonics, Death, Neuroscience

Robert White on brain death

Robert J. White is most known, or perhaps most notorious, for his work on primate head transplants. Less known, but more relevant to the practice of human cryopreservation, is his work in cerebral ischemia, hypothermia, and brain preservation. Most of White’s innovative work was published in the 1960s and 1970s. White also published a substantial number of opinion pieces on a variety of topics. One of these topics is brain death.

In an 1972 editorial for the publication Hospital Progress, “The Scientific Limitation of Brain Death,” White notes that:

…we have to acknowledge the probability that eventually all of the major cellular complexes of the human body will be replaceable either by transplanted organs (man or animal) or by sophisticated engineering modules.

As a consequence, the clinical definition of death is shifting from cardiopulmonary criteria to the central nervous system. But unlike other organs,

…this system is not replicatable, representing as it does the repository of the highest functions of man…when this elite cellular system fails it would seem reasonable to assume that what is characteristically ‘human’ is also being lost from the body.

But just as the cardio-respiratory definition of death has evolved and changed with the clinical practice of cardiopulmonary resuscitation,  a similar fate may be in store for the definition of brain death. The clinical use of general anesthesia and hypothermic circulatory arrest, in which the brain can be put “on pause,” emphasize how important the aspect of “irreversibility” is.

As presently defined, the definition of brain death puts much emphasis on brain function upon physical examination. A major limitation of this definition is that it categorically ignores the prospect that brain function could be restored in the future by technologies more advanced than practiced today, provided the material basis of brain function is preserved.

Another challenge is that the science of cryobiology has advanced to such a state where brain slices can be preserved at subzero temperatures and recovered without loss of viability through vitrification. When recovery of organized electrical activity can be demonstrated in vitrified mammalian whole brains, the prevailing definition of brain death will need to be challenged again because it will open the practical possibility to maintain critically ill people in a state of low temperature circulatory arrest without producing one of the indicators of irreversible brain death. Such advances would be an extension of the  experiments Robert White did on isolated hypothermic brains.

As White stresses in the final paragraph of his paper:

…like all biological activity, life and death merge into one another representing a continuum and the neuro-scientist can only in the final analysis determine the point of irreversibility of this highly complex system at which the possibility of organized activity that characterizes human behaviour  has been exceeded.