WHAT IS "BRAIN DEATH" AND HOW IS IT DIAGNOSED?

The concept of total "brain death" as an alternative to the older definition of irreversible circulatory-respiratory failure was first introduced in a 1968 report authored by a special committee of the Harvard Medical School [1] and was later adopted, with some modifications, by the President's Commission for the Study of Ethical Problems in Medicine and Biomedical Research, as a recommendation for state legislatures and courts [2]. The "brain death" standard was also employed in the model legislation known as the Uniform Determination of Death Act which has been enacted by a large number of jurisdictions and the standard has been endorsed by the influential American Bar Association. While New York is one of the few jurisdictions that does not have a "brain death" statute, it has adopted the identical rule through the binding decisions of its highest court. The rapid, and near universal, acceptance of neurological criteria of death is probably attributable to three factors. First, moving the time of death to an earlier point facilitates organ transplants, and indeed makes such transplants possible. Organs, especially hearts and livers, are suitable for transplantation only if they are removed at a time when blood is still circulating. Once cardiac arrest stops circulation, rapid tissue degeneration makes the organ unsuitable for such use. Given the increasing success of these operations and the relative uselessness (from a secular standpoint!) of sustaining "brain dead" patients on respirators, there is a natural temptation to redefine death so that organs become available to serve higher ends. It is no coincidence that the movement towards acceptance of "brain death" coincided with the development of cyclosporine and other anti-rejection drugs.

Additional considerations involve triage and allocation of scarce medical resource. It is extraordinarily expensive (in terms of equipment and labor) to maintain patients on respirators and other life support and using these resources for "brain dead" patients prevents their deployment for those who stand a better chance of recovery. Yet a third impetus towards redefinition is an understandable desire to spare families the agony and anguish of watching a loved one experience a protracted death.

For whatever the reason, the current definition of "death" is now a composite one: death is deemed to occur when there is either irreversible cessation of circulatory and respiratory functions (the "old" definition) or irreversible cessation of all functions of the entire brain including the brain stem. The principal utility of this second standard permits declaring as dead a comatose, ventilator-dependent patient incapable of spontaneous respiration but whose heart is still beating due to the provision of oxygen via an artificial breathing apparatus.

At the outset, two points must be made absolutely clear. First, contrary to the misperceptions of many lay people, "brain death" is not synonymous with merely being comatose or unresponsive to stimuli. Indeed, even a flat EEG (electro-encephalogram) does not indicate brain stem destruction. The human brain consists of three basic anatomic regions: (1) the cerebrum; (2) the cerebellum; and (3) the brain stem consisting of the midbrain, the pons, and the medulla, which extends downwards to become the spinal chord. The cerebrum controls memory, consciousness, and higher mental functioning. The cerebellum controls various muscle functions while the brain stem controls respiration and various reflexes (e.g., swallow and gag). A patient may be in a deep coma and nonresponsive to most external stimuli but still very much alive. At most, such patients may have a dysfunctional cerebrum but, by virtue of the brain stem remaining intact, are capable of spontaneous respiration and heartbeat. Indeed, the most famous of these cases, Karen Ann Quinlan, was able to live off a respirator for almost a decade. While such persons may be popularly referred to as brain dead, they are more accurately described as being in persistent vegetative state [PVS] and are very much alive under both secular and Jewish law. Removal of organs such a donor would indisputably be homicide. This is even more true for the phenomenon known as being "locked-in" where the patient is fully conscious but unable to respond.

A second point to keep in mind is the relationship among respiration, circulation, and the brain. The heart, like any organ, or indeed cell, needs oxygen to survive and without oxygen will simply stop beating. Respiration, in turn, is controlled by the vagus nerve whose nucleus is located in the medulla of the brain-stem. The primary stimulant for the operation of the nerve is the presence of excess carbon dioxide in the blood. When stimulated, the nerve causes the diaphragm and chest muscles expand, allowing the lungs to fill with air. Spontaneous respiratory activity can therefore not continue once there is brain stem destruction or dysfunction. The heart, on the other hand, is not controlled by the brain but it is autonomous. It is obvious, of course, that the brain­stem will inevitably lead to cardiac cessation not because of any direct control the brain stem exercises over the heart but simply because the heart muscle is deprived of oxygen. Where, however, the patient's intake of oxygen is being artificially maintained, the heart may continue to beat blood and circulate for a considerable amount of time after the total brain-stem destruction. The time lag between brain death and circulatory death is on the average only two to ten days, though there is at least one case on record where a woman's heart continued to beat for 63 days after a diagnosis of brain death. (Indeed, she delivered a live baby through Caesarean section.) It is this crucial gap between cessation of spontaneous respiration and cessation of the heart beat that defines the parameters of the phenomenon called "brain-stem death."

The steps taken in a clinical diagnosis of "brain-death" vary from medical center to medical center and those differences may have significant halachic repercussions but will typically involve the following: (1) a determination that the patient is in a deep coma and is profoundly unresponsive to external stimuli; (2) absences of elicitable brain-stem reflexes such as swallowing, gag, cough, sigh, hiccup, corneal, and vestibulo-ocular (ear); (3) absence of spontaneous respiration as determined by an apnea test; and (4) performance of tests for evoked potentials testing the brain-stem's responsiveness to a variety of external stimuli. These tests are to be repeated between 6-24 hours later to insure irreversibility - with life support supplied for the interim - and a specific cause for brain dysfunction must be identified before the patient will be declared dead.

An additional test that is sometimes employed (when other clinical tests are deemed inconclusive) is radionuclide cerebral angiography [nuclide or radioisotope scanning]. A harmless radioactive dye is injected into the patient's blood-stem, typically through the intravenous tubing already in place. In brain-dead patients, scanning will reveal an abrupt cutoff of circulation below the base of the brain with no visible fluid draining away. While many observers have described this test as nearly 100% accurate, others have claimed the brain-stem circulation, especially in the medulla, is not well visualized and absolute absence of blood flow to this region cannot be diagnosed with certainty.

Note that a patient who is brain dead may theoretically continue to have muscle spasms or twitchings or even sit up. Whether this so-called Lazarus Reflex is an indicator of life will be discussed in due course; what is undisputed is that such movements are coordinated from the brain from the brain but solely from the spinal cord. It should also be noted that there are several instances of clinically brain dead patients carrying live babies to term. Again, this may or may not be significant.

2. President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research, Defining Death: Medical, Legal, and Ethical Issues in the Determination of Death (Government Printing Office, 1981).

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