Brain death, the social construct
Before we realized the true importance of the human brain, and its role in human consciousness, communication, and behavior, whenever the body would die, the brain would die. It all kind of happened together. The heart would stop beating, the lungs would stop breathing, and eventually oxygen and vital nutrients would not be transported into the nervous system. Once the heart or lungs stopped, the brain stopped. At least that’s what happened until the middle of the twentieth century. Death was a total body experience. Until we learned how to artificially support failing organs. But how did our definition of “death” change once a pulse could be maintained almost indefinitely? In this week’s installment of BrainWaves, Drs. Mike Rubenstein and Joshua Levine join me to discuss the history of the semantics behind brain death, and why with all of its problems, we still need it.
In 1780, Chaussier invented the first commercialized device to apply positive pressure in surgical patients, a bag-and-mask mechanical ventilator. A negative-pressure ventilation device wasn’t available until 1838 when Scottish physician John Dalziel invented the “tank ventilator.” Imagine crouching inside of an airtight box with what looks to be an accordion pumping air in and out of the box. Eventually modifications were made to this small box, and patients could lie down inside of it with only their heads exposed. The use of such a ventilator was immediately obvious to many hospitals given the polio outbreaks of the early twentieth century. Boston Children’s Hospital actually developed multi-person ventilators that would have enough room for 4 patients in a single machine (below).
And in 1947, Claude Beck successfully defibrillated a human heart. So now cardiac death could be prevented. Where once the absence of pulses indicated death, now pulses could be restarted, and failing lungs could be ventilated. But what did this mean for patients whose brains did not so easily recover from massive anoxic injury, trauma, infection, tumor, or hemorrhage? You can imagine that the usefulness of an artificial breathing apparatus created an unprecedented ethical dilemma. Physicians asked themselves, “Is this patient whose heart is still beating and lungs are still breathing alive?”
In the podcast, we talk about the limitations of the term, “brain death”. For instance, it suggests that the units constituting the brain (the neurons, glia, blood vessels, and associated tissue), are all individually dead cells. That is not the case. “Brain death” also indicates that there is more than one kind of death. Previously, I guess you would say there was just “cardiac death”. But death is death. There just happen to be other ways to do it now. Because of these, and other criticisms of the semantics behind “brain death” (lots of air quotes in this episode), some have referred to it as “death by neurologic criteria.” And in 1968, when the concept really took hold in the US following publication of the Harvard Ad Hoc Committee’s Report, the term “irreversible coma” was used as a criterion for death. Whatever you believe, the 1981 United States Uniform Determination of Death Act allows death to be determined in two ways: by cardiac evaluation or by neurologic evaluation. But how does one proceed with a neurologic determination of death, and where did these steps originate?
As one of the authors for our institution’s policy on determining brain death, Dr. Levine’s expertise is much appreciated here. Our current standards, based on the 1995 American Academy of Neurology Guidelines, rely on 3 criteria for determining death by neurologic criteria.
- Coma, or lack of responsiveness to external stimuli
- Absence of brainstem activity, by physical assessment
What becomes apparent in this week’s episode is that these three criteria aren’t much different than the original criteria proposed by Pierre Mollaret and Maurice Goulon in 1959. These physicians described the neurologic exam findings of 23 patients who eventually progressed to multi-organ failure and death, and they call this physical state, coma dépassé. It was not death, per se, but it was a condition that invariably led to death. Four years later, in Boston, Robert Schwab proposed a triad of criteria for “death in spite of cardiac action”, which built on concepts divined by Mollaret and Goulon. These included:
- Fixed and dilated pupils, no elicitable reflexes, and no spontaneous movements
- An isoelectric EEG
At the same time that critical care physicians were resuscitating patients and maintaining them on artificial life support, and neurologists were trying to define whether the brain was reversibly or irreversibly injured, surgeons began transplanting organs. It seems to be a bit of a coincidence, but just at the time when living, perfused organs were needed for healthy transplant recipients, defining whether the organ donor was alive or dead became a major biological, legal, and ethical dilemma. It became obvious to surgeons in the mid-twentieth century that organs harvested from living donors were more viable than organs obtained from deceased donors, organs from cadavers. So, now that people could be placed on artificial life support even if they otherwise would have died, when could a surgeon take a liver or a lung from a patient whose heart was still beating, or lungs were still breathing?
- (1954) First successful live kidney transplant between identical twins
- (1962) First successful cadaveric kidney transplant
- (1963) First successful lung and liver transplants
- (1967) First successful cardiac transplant by Christiaan Barnard in South Africa
Regardless of whether there may have been a conflict of interest among twentieth century surgeons, at the dawn or organ transplantation, there was no consensus among physicians as to when a patient may be dead if he or she were mechanically ventilated. Surgeons needed something more concrete in order to justify organ harvesting from people whose bodies were no more than vessels for organ viability. So, in 1968, a group of physicians in Boston published a consensus statement titled, “A definition of irreversible coma.” The 1968 report of the Ad Hoc Committee was important for many reasons. First, it emerged out of a growing need to identify irreversible injury regardless of the advances made in critical care and resuscitative medicine. Also we needed to clarify which patients could be organ donors, now that they were officially declared dead. The Harvard report also required that irreversible coma be confirmed on a second exam 24 hours later. And to meet criteria for irreversible coma, the following must be true:
- No response to external stimuli
- No spontaneous movements or breathing
- No reflexes
- Isoelectric EEG
Are you seeing the theme here? And while there was not much in the way of updates in clinical practices between each of these definitions, even this Harvard report was not without flaw. It did not require that confounders be excluded, for one. A patient could be hypothermic, sedated, or severely hyponatremic. And these can mimic brain death. For another, the Harvard report did not discuss limitations of testing, and what to do when results were inconclusive. How we get to these results, and how we actually do a brain death examination today, will be the subject of next week’s episode. Additionally, next Thursday, we’ll dive a little deeper into all the shortcomings of a brain death evaluation. So don’t die on me before then.
BrainWaves’ audio podcasts and online content are intended for medical education only and not for routine clinical practice. Anything discussed here should not be used to determine brain death or any other kind of death. Please refer to your local, regional, or national policies.
- Kacmarek RM. The mechanical ventilator: past, present, and future. Respir Care. 2011;56:1170-80.
- De Georgia MA. History of brain death as death: 1968 to the present. J Crit Care. 2014;29:673-8.
- West JB. The physiological challenges of the 1952 Copenhagen poliomyelitis epidemic and a renaissance in clinical respiratory physiology. J Appl Physiol (1985). 2005;99:424-32.
- A definition of irreversible coma. Report of the Ad Hoc Committee of the Harvard Medical School to Examine the Definition of Brain Death. JAMA : the journal of the American Medical Association. 1968;205:337-40.
- Wijdicks EF, Varelas PN, Gronseth GS, Greer DM and American Academy of N. Evidence-based guideline update: determining brain death in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2010;74:1911-8.