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The Clinical Determination of Brain Death: Rational and Reliable
03 April 2015 (online)
Any physician is able to confidently diagnose the death of a human being. Most of the time it is cardiac standstill, and the event—using simple clinical criteria—is determined by no consciousness, no breathing, no circulation, and no capacity of resuscitation. To diagnose absent brain function—some call it death by neurologic criteria—is a more detailed examination best done by a neurologist or neurosurgeon. Of course, in principle, any clinically experienced physician is qualified to determine death by neurologic criteria, but in our hospitals we noticed an increase in consulted neurointensivists, and perhaps this can be attributed to a poor comfort level of physicians less familiar with disorders of the nervous system. The diagnosis of brain death is neurocritical care territory because it gets to the fundamentals of pathophysiologic processes associated with acute brain injury.
What is brain death? When do we conclude the patient is brain dead? Every so often I want to emphasize that we must look under the tentorium. The main structure of interest for neurologists is the brainstem and always has been. Thus, the irreversible absence of functions of the brainstem is the necessary and sufficient component of brain death, and this can be assessed and diagnosed clinically at the bedside. Any type of brain stem injury is already very important in prognostication. In fact, assessment of outcome is more reliable when there is permanent brainstem injury, and neurosurgeons usually do not intervene anymore when the brainstem is substantially injured (with the notable exception of acute hydrocephalus and cerebellar hematomas). No clinically measurable brainstem function equals brain death and death. It is unconscionable that some brain death guidelines have stipulated that even more electrical and blood flow tests are needed when the brainstem is primarily damaged. There is so much irrelevance in these ancillary tests, and one can easily argue that patients who are clinically dead do not need confirmation. There should be little misunderstanding that irreversible cessation of brainstem function is the indicium of loss of all other brain function. I am particularly baffled when it is suggested that patients with no brainstem function might be “locked in” with functioning thinking parts of the brain. In cats, acute isolation of the brain from the upper brainstem through complete cut through transection (cerveau isolé) produces persistent coma with a continuous pattern of spindles and slow waves on electroencephalogram (EEG), and there is no reason to believe it is different in humans.
In virtually every situation, brainstem injury is secondary to massive hemispheric injury shifting and damaging the brainstem, or it is part of a global insult to all parts of the brain (i.e., prolonged cardiac arrest). In essence, when all brainstem reflexes are absent in an undrugged apneic patient—and after all medical and neurosurgical options have been considered and tried—there is an irreversible finality. Not only personhood, but also life as we define it is gone.
The medical profession and its medical organizations consider brain death the death of the individual. There are those who would claim that the definition of death cannot be based simply on medical judgment, but should be based on philosophical, religious, and other conceptional categories. Some scholars opine based on theoretical analysis, and claim death after catastrophic brain injury is unknowable. Some may think that a clinical diagnosis infers a characteristic pathology, but not so. Prolonged comatose states and brain death may have similar neuroimaging and autopsy findings. All of these discussions are somewhat pointless if we simply accept that permanent loss of all measurable brainstem function equals death.
The diagnosis of brain death should be straightforward, clear, and reliable. From time to time, it is useful to revisit this topic. This collection of reviews summarizes the main areas of interest concerning clinical determination of brain death, but also ventures into current debates. The authors have been carefully chosen and present the current state of affairs partly based on their own work and partly based on review of current studies. Unavoidably, as the editor of this series of papers I may leave my imprimatur, but I think both sides of the arguments are presented well, though I accept that some of the readers may not fully endorse the opinions voiced in this compilation and I may disagree with some of the statements. Readers can find summaries of clinical criteria of brain death in adults and children in the United States and a thorough discussion of guidelines used elsewhere in the world. The degree of variability is dizzying, and with so much technical variation in guidelines one would feel an urge to do something and improve uniformity of practice, but there are some who would say, “Vive la différence.” Given this tremendous variation among countries and lack of progress since a survey a decade ago, it remains unclear whether a worldwide consensus on brain death determination can be achieved. The American Academy of Neurology practice guideline is a possible starting point because it has eliminated unnecessary tests, observation delays, and summarized the procedure in 25 simple verifications. Some options are presented to standardization, but let's face it, progress is doomed if we continue to focus on increasing safeguards that only lead to more requisites, more tests, and more regulations. A physician who is not confident (or capable) should not do it.
There is a sense that medical training— even at a fellow level—is insufficient also because brain death determination is infrequently done. Education of physicians can be improved and teaching brain death determination through complex simulation scenarios is discussed. There is a review of legal obligations in the United States and how courts can get involved and how the whole situation can journey away from a few simple medical facts. The legality of determination of death after a neurologic examination has not been disputed, but it is alarming to realize that challenges surface sporadically. Finally, and most importantly, support of the family of the patient is reviewed because care of the family member is paramount and its need is greatly underappreciated. Patients are typically unexpectedly acutely comatose and on a ventilator, with little time for the family to wholly grasp the nature of the situation. Many are flustered, unbalanced, and unable to take in information.
The diagnosis of brain death allows organ retrieval after consent is obtained. Although the two processes are completely different, they clearly overlap, which puts the attending physician in the role of a gatekeeper. When care is undeniably futile, contact with organ procurement agencies can be made for a quick orientation in eligibility. Organ donation agencies become active only after brain death is declared and both parties have always wanted it that way. Much good can come out of organ transplantation. There is no disagreement there.