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Brain Death


Brain Death

Part 1: [8 minutes  47 seconds]
alt Part 2: [6 minutes  48 seconds]
alt Part 3: [7 minutes  26 seconds]

Brain Death: Developing an Understanding
Discussions with Neurosurgeons
HODS on CNN
Date:
Participants:
William Sweet, MD, D.Sc.
Neurosurgery
Massachusetts General Hospital
Peter McL. Black, MD PhD
Chief of Neurosurgery
Brigham and Women’s HospitalLawrence Pitts, MD
Neurosurgery
San Francisco General HospitalBrian Andrews, MD
NeurosurgeryNarrator:
The diagnosis of death had always been a rather straightforward affair. (Film excerpt) Death was a condition which almost anyone could recognize. (Film excerpt) The deceased individual lay motionless and unresponsive and there were no signs of respiration or heartbeat. (Film excerpt) But times have changed. In his more than 50 years of medical practice, William Sweet, emeritus professor at Harvard has witnessed profound changes in the diagnosis of death.

William Sweet:
Yes, originally the millennia-honored method of diagnosing death, namely when you can’t feel any heartbeat, was the criteria. Indeed when I first began in medical school we weren’t aware that it was feasible to effectively start a heart that had stopped beating. When I went over to work with the British in WWII, here I found that they were starting the stopped heart and it would go on beating, and the individual would be usefully and effectively resuscitated, revived and lead a normal life. I found that pretty astonishing just by itself. It did make clear however, that the criterion of stopping of the heart being equivalent to death was wrong. Clearly the heart is just a pump; its work is effectively handled by a mechanical pump as by the human pump. And as we scrutinized the whole problem, then, we realized that the essence of the personality in the individual is the functioning brain. And that not until the heart has stopped long enough for the brain to die is the individual dead.

Peter McL. Black:

We’re built in a very peculiar way in the sense that we need to have the brain to breathe. We don’t need to have the brain to have the heart beat. and so if you can devise a way of keeping the respiration going, keeping us breathing, then you can keep the heart going even though the brain is completely destroyed and that’s the change that occurred in the middle of the 20th century. The development of good ventilators, the development of

intensive care units that allowed you to keep patients ventilated and perfused using their own hearts in situations that 20 years before would not have been possible because when the brain stopped, the patient would stop breathing, the heart would stop, and that would be the end.

William Sweet:

And it’s only gradually that we grasped the point that it’s only when the brain is dead, that the individual is dead. Not only is there such a thing as brain death, that’s the only death there is! You’re not dead until your brain is dead.

Narrator:

The real impetus to think hard about this problem came with the advent of heart transplantation. In 1968, the Harvard Medical School asked Harry Beecher, the Chief of Anesthesiology of the Massachusetts General Hospital, to examine brain death. Realizing the broad medical and social implications of this issue, Beecher created a special Ad Hoc committee. The committee members represented many areas of medicine, the law, history and theology. William Sweet was a member of the committee. After months of deliberation the Ad Hoc Committee arrived at a consensus, and in August 1968 their report appeared in the journal of the American Medical Association. The report contained a set of characteristics of a permanently non-functioning brain: the so-called Harvard Criteria. Although the criteria were widely accepted by many members of the medical community, some centers found them too conservative. In the decade that followed, medical centers from around the country, and indeed from around the world, studied brain death and presented their own guidelines, over thirty different criteria in all. Part of the controversy was just how much of the brain has to be dead before the person is dead.

Peter McL. Black:

Roughly speaking there are three positions to take on the question of how much of the brain has to be gone before a patient is dead by brain criteria. One says it’s the cortex. Now the cortex is what allows us to interrelate. And you can say that then if your crucial issue is can you make relationships with other people, then cortical death is enough. Another possibility is to say that brainstem death is enough, this is what’s done in England. That what you have to show is that the brainstem isn’t functioning. In America, being the great compromisers we are, we say let’s put ‘em all together. You have to have the cortex, you have to have the brainstem and you have to show that both of those are irreversibly gone before you can make the diagnosis.

Narrator:

The most comprehensive examination of brain death was the collaborative study conducted by the National Institutes of Health which was completed in 1973. Nine centers from across the country studied the outcomes of 503 patients. Finally in 1981, a Presidential Commission reviewed all the existing criteria and presented a report which represented a consensus of opinions from around the nation. Lawrence Pitts was an advisor to the Commission.

Lawrence Pitts:

They, with their large agenda, took on brain death as one of the issues, examined it carefully from a legal standpoint – – looked at the laws in the various states, looked at from a medical or technical standpoint- just how one declares brain death. And I think pulled together, I think, appropriate experts and were able to crystallize the medical issues surrounding brain death.

Narrator:

The criteria which emerged from the President’s Commission are now the cornerstone of most protocols. There are two key factors in the diagnosis of brain death: the loss of all cerebral and brainstem function, and irreversibility. The basis of this determination for the neurological examination of the patient.

Lawrence Pitts:

The technical diagnosis of brain death is really a low technology, fairly straightforward neurologic examination in the main and the tools that you need for that are no more complex than one uses for a routine neurologic exam. You need a flashlight, you need a pen, you need a reflex hammer, you need a tongue blade, that’s about all you need fro the brain death examination.

Narrator:

The neurological examination can asses the status of both the cerebral hemispheres and the brainstem.

Brian Andrews:

Specifically, functioning of the cerebral hemispheres can be assessed by evaluating the patient’s level of responsiveness. The brain dead patient has no responsivity to any stimulation including verbal stimuli or painful stimuli. Most frequently we use superorbital nerve compression to provide our painful stimuli. This avoids the possible lack of transmission of painful stimuli from the digits or the body if there’s an associated spinal cord injury.

Peter McL. Black:

What we’re trying to do is to show that the brain has been destroyed. The spinal cord is not relevant to what we’re talking about and therefore the tendon reflexes which are really segmental reflex to spinal cord function are almost a priori excluded from the determination of brain death. When I’m talking about tendon reflexes, I’m not talking about posturing which is something that as a response requires part of the brain.

Narrator:

The examination of the brainstem focuses on the presence or absence of the cranial nerve reflexes. First, the pupillary reflex is tested, and there should be absolutely no responsiveness of the pupils to light. Second, the corneal response, a fifth nerve reflex is tested and there should be no blinking in response to touching the cornea. Third, the oculocephalic reflex should be tested, and there should be no response to the so-called dolls eye maneuver with rotating the head from side to side. Fourth, the occulovestibular reflex must be evaluated, and there should be no deviation of the eyes from midline

despite irrigation of the ears with a cold saline solution. Fifth, an assessment of the lower brainstem should be performed, and there should be no gag or cough. And finally, determining if apnea is present.

Lawrence Pitts:

At the very bottom of the brainstem, that is in the medulla, are the centers that drive respiratory function and in the brain dead individual there will be no respiratory drive and no breathing. And it’s important to prove that. In most instances where one is determining brain death, the patient is already on a ventilator, and one doesn’t know whether some minor ventilation drive may be present or not. So it’s important to test for that and determine reliably if the patient shows any ventilatory effort or not. And it’s done simply by a thing called apnea testing.

Narrator:

The following procedure is recommended. The patient should be ventilated with pure oxygen or an oxygen and carbon dioxide mixture for ten minutes. A baseline blood gas should be measured and in most cases the PaCO2 will be in the range of 35 to 40 millimeters. The ventilator is then turned off and oxygen is allowed to flow passively through an endotracheal catheter. The patient should be watched for any efforts to breathe or any indications of cardiac instability such as bradycardia or cardiac arrhythmias, in which case ventilator support should be reinstated immediately.

Lawrence Pitts:

It’s kind of the last test that you do testing for brain death. The reason for that is that it’s the bottom of the brainstem it does require stopping the ventilator, gearing up a little bit to do it. So it’s slightly harder to do than just checking the pupil response. And probably the most important reason for saving it for last is that if one plans to terminate the care of the patient at that point then you would just not put them back on the ventilator and the heart would stop within a matter of minutes.

Narrator:

After 10 minutes blood gases should again be measured and the ventilator reconnected. If the PaCO2 has risen to 60 millimeters or above and the patient has not made efforts to breathe apnea has been established. In certain cases, brain death cannot be determined on the basis of a neurological examination alone. In these cases, confirmatory tests may be used.

Lawrence Pitts:

Once in a while it is helpful to have technical confirmation of brain death. The best example I can think of is when a patient has been placed in a barbiturate coma by the physicians as a treatment for elevated intracranial pressure–being the most common use. When that occurs you cannot use the neurologic examination because you have put the exam to sleep basically with a barbiturate. You may still strongly believe at some point that a patient is brain dead, persistently high intracranial pressure. If ICP is as high as arterial pressure then no blood is flowing to the brain and the brain cannot live in that circumstance. One way to prove there is no blood flow to the brain is to do specific blood

flow tests; there are a variety of ones can that can be done. One that is easiest to do is a radionucleide study where an isotype is injected in a vein and a gamma camera is placed over the head and when one can show no radioisotope going into the brain then there is no evidence of blood flow. Another form of blood flow is the old style angiogram where contrast material is injected into the carotid artery, and if it doesn’t flow into the brain then blood is not flowing into the brain and the brain cannot live without oxygen and nutrients being delivered by the bloodstream. So, absence of blood flow is indeed brain death.

Lawrence Pitts:

The EEG test may be useful when there is substantial physician uncertainty about the diagnosis of brain death. For instance, if a stroke perhaps has occurred, the magnitude of the stroke or the exact importance of the stroke is a little hard to determine say from a CT scan which would take perhaps days to evolve to the point where you would see overwhelming brain injury. There is no requirement for an EEG in the determination of brain death. There is a requirement that you be as sure as you can be that irreversible damage has occurred and so if the physician feels unclear and wants the extra information then one EEG or, if the physician is particularly uncertain, EEG’s separated in time, perhaps six or twelve hours might be useful. But the EEG is not invariably reliable; there are times when very low level signals appear to be brain activity, but subsequently turn out to be artifact or some other technical problem, and in fact the patient is brain dead. If bonafide EEG traces are available, and one can be certain about that then, by definition, brain death is not present and one would negate the tentative diagnosis of brain death with a truly positive EEG.

Peter McL. Black:

Even the Harvard group did not say the EEG was absolutely necessary; it was recommended and subsequently we’ve moved back even from that kind of approach to say that the EEG is a good idea as an ancillary test, but there are other ancillary tests. And in fact, none of those is necessary. In fact, it’s enough looking at the clinical state of the patient in the appropriate setting to be able to make the diagnosis without any EEG, without blood flow tests, without anything else.

Narrator:

The second element in determining brain death is establishing the irreversibility of the condition.

Peter McL. Black:

In the most recent formulations, the important elements in irreversibility have been having a known cause of the coma, so that you know that the natural history of that disorder is to go on to increase trouble and then to exclude some conditions which may mimic brain death. Specifically, drug intoxications of various kinds, very low body temperature, very low blood pressure.

Lawrence Pitts:

For instance, a patient who is intoxicated with barbiturates to a very deep level will look brain dead. They will have no demonstrable brain function and yet if you didn’t know the diagnosis that’s a completely reversible intoxication with barbiturates you’d call them brain dead incorrectly because they would have lost all brain function but not irreversibly.

Peter McL. Black:

I think that a screening for barbiturates, perhaps Valium, needs to be done on most patients in whom you’re trying to make the diagnosis. But I think that if, especially if there is a huge hematoma or a huge infarct in the brain, that a small amount of intoxicant drug really isn’t going to make a big difference.

Narrator:

A key to determining irreversibility is the persistence of the loss of brain function over time.

Peter McL. Black:

The period of time, required to make the diagnosis of brain death has varied a little depending on the criteria that is used. When the Harvard committee first set up its criteria the main goal was to be as conservative as possible. And under that framework the concept was that 24 hours would be a minimum time to be absolutely certain that there was nothing reversible about the patient’s state. When the collaborative study was done, by the National Institutes of Health, it appeared that 6 hours was a minimum time that was required to stabilize a patient and to try to be sure that drug intoxication or some of the other kinds of conditions that can mimic brain death were not relevant to this particular patient. And so subsequent criteria have varied between the 6 and the 24 hour period. But, one can think of a situation where at least from the time that the patient enters the emergency room, it may well be the case that 24 hours is not enough. I think most of us would feel, though, that if you have the appropriate pre-conditions for making the diagnosis that in fact 24 hours is long enough to establish that that condition is irreversible.

Narrator:

The final factor influencing the determination of brain death is the age of the patient. The NIH study and the President’s Commission stated that their criteria did not apply to children under five years of age. In 1987, a national task force was organized to examine the criteria for the determination of brain death in children.

Peter McL. Black:

My interpretation of the recent task force guidelines for children is that they more or less extend the kinds of criteria we’ve used for adults to children with some very important exceptions. One is that premature infants need to be excluded still, and also that neonates up to at least a week need to be excluded. They emphasize the importance of knowing the cause of the coma, and then there are a series of recommendations for the time period required for the determination which must be followed depending on the age of the patient.

Narrator:

All of the protocols for determining death by neurological criteria allow the clinician the flexibility necessary to tailor the diagnosis to each case.

Peter McL. Black:

I think there are two critical points in this business of the variation of brain death criteria. One is that the institution somehow have a policy which is clear for making the diagnosis in its patients. The second thing, and something that I can’t emphasize too much, is the importance of good documentation of whatever criteria you use. It’s certainly not enough in a record to say “No neurologic function; patient fulfills brain death criteria.” What you have to put down — what the things you tested were, how you did the tests, the time that they’re done and make absolutely sure that the record demonstrates that the appropriate kinds of tests for that determination were done in this particular patient. I think that that’s terribly critical in making the diagnosis no matter what the criteria you use are.

Narrator:

The key to establishing trust in the diagnosis of brain death is confidence in the validity of the criteria which are used.

Peter McL. Black:

I think the question of how confident we can be about brain death criteria in the end boils down to what the justification for the criteria themselves might be. The recent Presidential Commission guidelines really came out of the National Institutes of Health collaborative study. Now the fact that these criteria came out of that study suggests that they really are legitimate in some important sense. The steps that we’ve taken so far in the United States have been well-justified by data collected in a careful way. And I think that we can therefore be confident about the criteria being careful, progressive steps in our understanding of how one makes the diagnosis of a dead brain in a body whose heart is beating.

William Sweet:

As far as I know, there has never been a case reported of an individual who met the criteria that original Harvard Committee who survived to tell the tale.

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