Part-3
Brain Death
[Part 3: 7 minutes 26 seconds]
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.