Part II: The Hand of God?—Looking at Brain Death
By Edison McDaniels, MD | surgeonwriter.com
You might want to read the first article in this nonfiction series first. [Click Here]
Keywords: nonfiction, brain death, coma, CT, MRI, miracle
Recently, I proposed a heart-breaking scenario, a badly injured man, surrounded by loved ones, apparently brain dead—who lives to defy his physicians.
Do such miracles really happen? Can a person really come back from brain death?
As a neurosurgeon, I have been involved in too many brain death scenarios to count. Let me say at the outset I have never encountered a hand of God miracle—not around the issue of brain death anyway.
That said, I have seen several patients I didn’t expect to survive—let alone thrive—do both. But that’s not the same thing. These patients were badly injured, but not brain dead. Some were in a coma, but that’s not the same as brain death. As a brain surgeon, I can tell you unequivocally it’s not possible to foretell how well a badly injured brain will recover. I’ve been surprised by this more than a few times. People I expect to do well don’t, and people I expect won’t do well do.
It’s a matter of pathophysiology—we can often see the injury on our tests, but not how that injury will play out functionally with the rest of the brain. It’s a matter of function. We can’t see physiology in action on a CT or MRI. Note: we can see physiology in action on a PET scan, but these are used more for research than clinical decision making and not widely available in most hospital settings.
That’s fundamentally different however from brain death. In brain death, we aren’t looking at physiology but function—or rather the lack thereof.
Here’s a truism. The best test of how somebody is doing neurologically (that is, how their brain is functioning) is not a CT scan, MRI, or EEG. The best test to see how somebody is doing neurologically is to observe how they actually behave. That’s right. Forego all the expensive state of the art tests and actually observe the patient.
Do they respond to their own name?
Are they moving their arms and legs? Either spontaneously or to stimulus (such as the prick of a needle to draw blood)?
Do they speak, or attempt to speak?
Do they open their eyes?
Do they gum the breathing tube with their mouths?
Do their pupils respond to light?
Do they move when the sedation is removed?
Do they attempt to breathe on their own when the ventilator is turned off?
If a patient does any of these things, their brain may still be badly injured but they aren’t brain dead. And if they aren’t brain dead, it is extraordinarily difficult to foretell how far somebody will progress along the road to recovery (though if the injury is severe enough to be asking these questions it is unlikely they will recover to be the exact person they were before the injury).
But this still doesn’t help us with brain death. A patient who does none of the things listed above is not necessarily brain dead. Indeed, most of the time such a patient is not brain dead, but in a coma. Coma is not brain death.
So how do we, as physicians, know when a patient is truly brain dead and not just comatose?
The definition of brain death is an irreversible cessation of all functions of the brain, including the brainstem (which houses the most primitive brain functions necessary to support life: heart rate, maintenance of blood pressure, and control of breathing). It must be noted that a patient determined to be brain dead is legally and clinically dead.
But, practically speaking, when is a person brain dead?
Answering that question can be surprisingly difficult for the neurologically unsophisticated. It turns out there are, in fact, several ways in which to show brain death. The summation of these will provide unequivocal evidence of brain death. All of these have to do with function and not just physiology:
- A cerebral angiogram that shows no blood flow to the brain. It is not possible for the brain to function in the absence of blood flow. This test is unequivocal.
- A CT of the brain with IV contrast that shows no blood flow to the brain. This test is unequivocal.
- An EEG that is flat line. The functions of the brain are transmitted via electrical pulses, which can be captured on EEG. In the absence of these pulses, there is no function and the brain is dead.
- The absence of all of these on exam: no pupillary light reflex; no movement or response of any sort to stimulation (such as grimacing or an increase in heart rate to a painful stimulus); no eye movement when the middle ear is stimulated with ice water (this is a severely uncomfortable stimulus in the living); no corneal response; no attempt at breathing when the ventilator is turned off (this is referred to as the apnea test).
For the apnea test to confirm brain death, the CO2 must rise above a certain threshold since, oddly, it is actually the level of CO2 and not the level of oxygen that stimulates breathing (this is why swimmers who hyperventilate and blow off CO2 may drown when the oxygen level falls before the CO2 level builds enough to force a breath; they pass out and drown when the rising CO2 causes them to inhale water).
In addition to the above, the patient must not be cold (hypothermia may simulate death), and there can be no sedating medications or paralytic drugs on board—a condition which is not always met in ICU patients who are frequently sedated and paralyzed to facilitate ventilation.
The law usually requires, and hospital policies usually demand, that two separate brain death exams be repeated six or more hours apart to confirm the results before they become official.
In my experience, and that of every neurologically sophisticated physician I have ever discussed this with, if the above conditions are confirmed, recovery is not possible and is never seen. So how then do we explain the all too common cases of so-called recovery from brain death?
That’s next time at Neurosurgery101—TheBlog.