Monday, February 9, 2009

When Do We Die?

We’re confused about death, despite the fact that is it so familiar and so common. Part of our confusion arises from a set of powerful superstitions and muddled myths about it.

The question of when a person dies is relevant to the God issue because so many evidential claims related to the afterlife, souls, immortality, transcendence, and even resurrection are so frequently made in conjunction with cases of human near death and death. It’s surprisingly common to encounter someone who insists that at one point during a medical procedure or after a car wreck they were “officially dead.” People who have undergone some physical trauma frequently claim to have had a near death or after death experience that is taken to be evidence of immortality or the survival of the soul. Such stories are titillating and get repeated endlessly to the point that they have substantially fortified views about the soul’s independence from the body. The stories fuels people’s false hopes, and amplifies the confusion. The more of these hope inducing cases people hear about, the less likely they are to face the brute medical facts and the less willing they are to acknowledge what we now know about death beyond any serious doubts.

The details: When a human being dies, accept under some extraordinary circumstances, it is better to consider their death to be a process that could take hours or even days surrounding the official pronouncement. There is no abrupt moment biologically when all bodily functions, all neurological functions stop. There are stages of increasing levels of tissue damage to more and more of the body’s systems, and as these stages advance, the likelihood of any resuscitation drops off dramatically. In the case of the brain and nervous system, as the damage proceeds, every indication is that the correlated functions of consciousness cease as well. (See my numerous other posts about the evidence concerning brain function and mental function.)

Clinical death is the cessation of blood circulation and breathing. As medical technology has advanced, the number of cases of clinical death where the patient is resuscitated and restored to full function has grown large. It has become increasingly possible to restore the beating of the heart and breathing.

Clinical death then, is not the irreversible end. The point at which resuscitation becomes exceedingly unlikely is brain death. After clinical death, oxygenated blood ceases to flow through the body. Without it, tissues begin to starve. Very soon, those tissues begin to die. Some of the most vulnerable tissues to destruction from blood and oxygen deprivation are neurons. After a few minutes, many areas of the brain are injured beyond repair. If resuscitation occurs 3 minutes or more after clinical death, then complete brain recovery is very rare. Damage to brain tissues occurs very soon after clinical death, but there is no established point or time beyond clinical death at which all brain functioning ceases.

The American Academy of Neurology’s guidelines for brain death are that the patient is unresponsive, there are no brainstem reflexes, and there is no breathing. http://www.aan.com/professionals/practice/guidelines/pda/Brain_death_adults.pdf

If a patient is clinically dead and brain dead, by these definitions, then the irreversible destruction of vital organs and tissues is rapid and widespread. It should be noted, however, that our methods for detecting brain activity or the proper function of brain tissues are still relatively crude. There are 100 billion neurons in the brain. All of them require oxygenated blood in order to function. During normal functioning, they develop ionized charges or action potentials that can be triggered by other neurons and that cascade outward to trigger the activations of other neurons.

When clinical death occurs, however, there are still countless electrical and chemical interactions that unfold. The cessation of all neural activity and the point at which there is irreversible damage to all of the brain could take a long time. The measures that doctors look for like the absence of brainstem reflexes indicate macro failures of vital systems in the brain, but they do not signal the end of all metabolic processes in the brain or body. Crude measures like EEGs capture large scale brain events, but not even the most powerful fMRI scanning machines we have today are capable of resolving the activity of individual neurons. fMRI machines detect relatively large volumes of oxygenated blood flow to regions of the brain. So it is reasonable to think that some neural activity will continue even after the macro indicators of brain function reveal no reactions. But even these lagging few neural events will taper off rapidly after the heart stops or there is other damage. It is not clear yet exactly how many and which neurons must continue to fire normally for the subjective experience of anything like consciousness or awareness to be sustained.

Let us call the absolute cessation and failure of function of all of the nerve cells in the body, absolute brain death. No one is revived from or survives absolute brain death. Occasionally people are resuscitated from clinical death. Even more rarely, patients have survived brain death. In many of those cases, the brain damage from the event remains and their cognitive functions are vastly impaired. In extreme cases, like Terry Schiavo, all of the so-called higher functions are gone and only the most rudimentary involuntary functions remain.

What about near death experiences? Can’t they provide us with evidence for life after death? The simple answer is no, not the ones that we typically hear about. For the most part, the stories about NDEs that we hear, if they are not fabrications, exaggerations, or mistakes, occur before clinical death, or perhaps between clinical death and brain death. No one is resuscitated from absolute brain death and comes back to tell us stories about the other side. This is important because that is precisely what would be required to make those stories interesting from a metaphysical perspective. If we could establish that someone’s brain had reached the point of absolute death, and yet despite lacking any neural function that might explain it, that subject had an experience of floating, moving towards the light, seeing Jesus, and so on, then we might have some testimonial evidence that would be important concerning the immortal soul.

The matter is further complicated by a timing problem. Suppose that Smith goes unconscious in the operating room at 10:00am on Monday, and then Smith becomes clinically dead at 10:45. But the doctors revive his heart and breathing by 10:46. And then Smith remains unconscious, recovering in ICU for two more days before gaining consciousness on Wednesday. After he wakes, Smith tells us that he has had a NDE, and that it has convinced him that there is an immortal afterlife.

In this particular scenario, and it is probably a common pattern, there was no point at which all brain function ceased. Smith never reached absolute brain death. He didn’t even reach brain death. The problem is that it is well established that the brain can produce all sorts of extraordinary experiences on its own without those experiences indicating anything real. Yours does it every night when you dream. So even though Smith can claim that he was dead (“clinically dead”), we have no reason to think that any sort of brainless existence occurred. And without that, there simply is no case whatsoever for any autonomous existence, or some separation of the soul from the body.

The other substantial problem here concerns the time. When exactly did Smith have his NDE? We are prone to assume that if someone says that they were “dead” and that they had an extraordinary experience, then they must have had it during the period when they were dead. We have seen that merely being clinically dead isn’t sufficient for out of body experience. But more importantly, how is it that Smith knows when the experience occurred? In our example, Smith is unconscious from 10:00am Monday until Wednesday. Are we convinced that if Smith says he went to some other place without his body that the experience could not possibly be something his brain cooked up over the course of two days of unconsciousness? We don’t have any reason here to think that the experience occurred at the same time as the spell of clinical death. And besides, given that clinical death is just the stopping of the heart and lungs, we don’t have any reason to attribute it to anything but faulty brain function.

Another important point is that despite the fact that there are billions of people now and in the past who have died on the planet, we do not have, that I am aware of, a single case of anything anomalous happening that might lend support to the afterlife claims. We don’t seem to have a single case that stands up to any serious scrutiny. No real communication with the dead, no one whose NDE can’t be easily explained neurologically, no significant empirical evidence.

But the question has been hopelessly muddled by so much widespread confusion about what it means to be clinically dead, brain dead, and what I have called absolutely dead. Human brains do weird and remarkable things when they suffer trauma or when the are subjected to extraordinary circumstances. And usually that makes it easy to explain what has happened when someone believes they have gone over to the other side.

8 comments:

Beer Drinking Lutheran said...

For me, it was in my baptism (Romans 6).

I'm glad that's out of the way.

Carlo said...

We haunt the Sac state philosophy department :)

Matt S said...

Kevin Nelson at the University of Kentucky, is actually writing a book about NDE's, and published an abstract last year or in 2007. His hypothesis, which seems to be well enough supported not just through medical research but a holistic kind of study of literature and anthropology and stuff (Or at least I remember seeing him reading old greeks and books about cannibals for his book), seems to suggest that when we "die" our body will release adrenaline and we go into REM sleep, producing a waking sleep state where the boundaries between dream and reality become blurred.

Additionally, it seems that Westerners see the light at the end of the tunnel and other "western" end of life images, while people in other cultures see triangles, rectangles, shinto temples, and whatever else is relevant to their culture...

M. Tully said...

When there is no further significant (and I'll leave to the philosophers what significant is) probability of restoring consciousness, defines human death.

The one thing that makes us human is our ability to communicate ideas. Without that ability, or anything other than a temporary cessation of that ability we are dead.

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