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Dr. Noam Stadlan, Assistant Professor
Department of Neurosurgery
Rush University
Chicago
What is the definition of death?
What is brain death?
What is whole brain death?
What is brain-stem death?
What is the difference between whole brain death and brain-stem death (BSD)?
Can a person wake up from brain-stem death?
Has anyone who is brain-stem dead ever started to breathe on their own or regain any mental or voluntary bodily life function?
How is brain-stem death determined?
What is Confirmatory testing?
How is whole brain death determined?
What do autopsy of dead patients by neurological criteria show?
Can any doctor declare a patient to be brain dead?
What is the difference between coma and brain-death?
What is persistent vegetative state (PVS)?
Will doctors refrain from administering full medical care if they know a patient has a signed organ donor card?
Question: What is the definition of death?
Answer: Historically, death was defined as unconsciousness coupled with irreversible cessation of breathing (respiration) and heartbeat (circulation). This definition is still very much in use today.
However, with the invention in the late 1950’s of ventilators, artificial breathing can support the heartbeat and the brain (Christopher Reeve was supported by a ventilator from the time of his accident until his death). In addition to ventilators which mimics breathing, artificial hearts and heart transplants can continue to supply oxygenated blood to the brain. The realization then came to the medical community that death is not defined as those functions which can be re-instituted artificially (breathing and heartbeat), but by the irreversible cessation of the most function and the beneficiary of both breathing and blood circulation, the brain. Therefore, a more advanced understanding of death was accepted by the medical community, and that is when the brain dies before the heart and respiration ceases, and this is known as neurological death or brain-death.
Accordingly, it is misleading to call a patient “brain-dead”, since that sounds as if the patient is alive and merely suffering from a condition. The brain dead patient is dead and the medical community knows this by the fact that the brain is dead.
Question: What is brain death?
Brain death is the cessation of life due to the irreversible loss of critical brain function. In other words, the brain has stopped working and will never start again. Brain death can happen in two different ways: by whole brain death, and by brain-stem death.
Question: What is whole brain death?
Answer: The brain mainly consists of the larger part of the brain (the cortex) and the smaller part of the brain (the brain-stem). Whole brain death is when the entire brain (both cortex and brain-stem) is not functioning, and medical tests show this to be irreversible.
Question: What is brain-stem death?
Answer: This is where the lower part of the brain, called the brain-stem, is not functioning and has no chance of ever functioning again. The brain-stem has many crucial functions, including the reticular activating system, an area responsible for activating and deactivating the rest of the brain. As a result of brain-stem death, none of the brain (including the cortex) will show any external evidence of working. The brain-stem also controls breathing, so that someone whose brain-stem isn’t working cannot breathe at all on their own, and is unconscious and whose beating heart is totally dependent on getting oxygen from a ventilator.
Question: What is the difference between whole brain death and brain-stem death (BSD)?
Answer: In both cases, there is a total absence of any response whatsoever to stimulation, and a total lack of breathing and total unconsciousness and no chance of recovery. The difference lies in the results of testing. In BSD there are instances where blood succeeds in reaching other areas of the cortex and there can be measurable electrical tracings as indicated by an EEG. This is not necessarily indicative of brain function but rather that some cells have electrical activity. Very much like a heart that stops beating has cells that that have electrical activity. Even with this activity, if the patient is brain-stem dead, there is no chance of recovering consciousness or breathing.
Question: Can a person wake up from brain-stem death?
Answer: No. No patient that was ever diagnosed brain-stem dead by adequate criteria (Clinical bedside testing, Apnea, and Brain Blood Flow Studies) has ever woken up from brain-stem death. Brain Stem death, according to the medical community, is death. And even though the heart now continues to beat because it is artificially being supplied with oxygen (by means of ventilator), ultimately there will be complete systemic failure and the heart will stop beating, usually with a few days.
Question: Has anyone who is brain-stem dead ever started to breathe on their own or regain any mental or voluntary bodily life function?
Answer: No.
Question: How is brain-stem death determined?
Answer:
STEP 1
The first step is to establish that a competent cause of brain-stem death exists. In other words, just because someone is unconscious, we don’t suspect that they are whole-brain or brain-stem dead. There has to be significant injury (trauma, stroke, swelling, etc.) to the brain that makes one suspect death by neurologic criteria. Sometimes, when the medical history is unclear, imaging studies, such as CT or MRI, are able to supply evidence that a trauma has occurred to the brain. In addition, reversible causes of deep coma, such as hypothermia (low body temperature), hypotension (low blood pressure), overdose of certain drugs (such as barbiturates, paralytics, etc.), and a small group of neurological conditions, must be ruled out.
STEP 2
Next is the physical examination of the patient. First and foremost, the patient must be unconscious in a very deep coma state, unresponsive to any stimulation, and not breathing on his or her own. In other words, there can be no response of any kind to voice, pain, or any stimulation. If there is any response, the patient by definition is not brain-stem dead.
STEP 3
Then the specific functions of the brain-stem are tested for even the slightest function. This means looking for reflexes whose pathways run through the brain-stem. If any of the reflexes are present, it means that those pathways still work, and at least part of the brain-stem is alive. Of the many neurological reflexes of the brain-stem, the 6 main reflexes are:
- Eye Reaction (Pupillary Reflex): Ordinarily pupils react to light (pupillary reflex). When a bright light is directed into the eyes, in a normal patient the pupils (the dark center of the eye) react and contract, becoming smaller. If pupils are fixed (no response) and dilated (large) there is no neurological response.
- Eye Movement (“Doll’s Eyes”)1: In a patient with a working brain-stem (even if asleep or unconscious) if the head is turned rapidly from side to side, the eyes will move in their sockets and remain fixed, “staring” straight ahead as if they are focusing on one spot. This is the result of a neurological reflex. If the eyes stay fixed in their sockets and the movement of the head from side to side bring the eyes along with it (called ‘doll’s eyes’), this demonstrates that the brainstem is not working.
- Eye Movement (“Cold Caloric”): When ice-cold water is injected into the ear of a normal person, it cools down the balancing mechanisms in the inner ear and triggers eye movement (called nystagmus.) When the brain-stem isn’t working, there is no eye movement in response to injection of cold water into the ear canal.
- Eye Reflex (The Blink, or Corneal, Reflex): When the brain-stem is working, the eyes blink when the cornea (the transparent part of the eye) is touched. When the brain-stem is not working, no blinking occurs, no matter what the stimulation to the cornea.
- Gag reflex: If you touch the back of the throat of a healthy person with a working brain-stem, it elicits a gagging reflex. When the brain-stem is not working, there is no gagging, no matter how great the stimulation.
- Apnea Test (absence of autonomous breathing): This is the most important test used to confirm brain-stem death. The short description is that the ventilator is shut off and if the patient is not breathing then this shows that the brain stem is not function.
The long is description involves understanding breathing. When breathing occurs, oxygen is brought into the body, and carbon dioxide is expelled. Therefore, breathing serves to increase the amount of oxygen in the bloodstream, and decrease the amount of carbon dioxide.
The impulse to breathe occurs when the level of carbon dioxide rises to a significant degree. The best test of the impulse to breathe is under conditions where the oxygen level is normal, but the carbon dioxide level is too high. This test can easily be done with appropriate attention to detail.
The respirator artificial ventilation tubing attached to the ventilator is removed from the patient (the tube going into the patient’s trachea is left in place), and oxygen is blown into the lungs. The patient is monitored either for a specific period of time (8-10 minutes), or until the carbon dioxide reaches a specific level. Any movement of the chest during the test is considered a sign of breathing and there are also monitors that can measure even the minutest movements of respiratory muscles. If the brain-stem is totally destroyed, no sign of breathing or attempted breathing will be seen.
Most hospital protocols require testing for brain-stem activity (some specifically require a repeat apnea test and not a reflex test) to be repeated anywhere from 6-24 hours later, in order to confirm absence of brain-stem activity.
Question: What is Confirmatory testing?
Answer: In addition to observing lack of neurological reflexes controlled by the brain-stem, (e.g. lack of breathing), there are a number of tests available to help assess brain function.
Imaging - CT and MRI scans are able to show the brain and see if any damage (e.g. trauma, bleeding, and swelling) is evident. If it is not, the diagnosis of brain death is doubtful.
EEG (Electroencephalogram) – The EEG measures the activity of brain cells. In some cases of brain-stem death, some electrical activity is sometimes seen in areas of the brain outside the brain-stem. In whole brain death, the EEG is totally silent. Other tests, such as brain-stem audio-evoked responses (BAER) measure the electrical activity of a specific pathway. The BAER measures how the brain responds to sound. In both brain-stem death and whole brain death, the BAER should show the absence of any response from the brain and the brain-stem.
Brain Blood Flow Studies – Brain Blood Flow studies document the presence or absence of blood flow to the brain:
- Angiogram - The standard (but most invasive) test is an angiogram. In this test, a dye that shows up on x-ray is injected into the arteries, and motion-picture x-rays (fluoroscopy) are taken to observe whether the dye enters the brain or not. The absence of blood flow to the brain confirms whole-brain death. In brain-stem death, there can be blood flow to parts of the brain, but not to the brain-stem.
- B. Nuclear Blood Flow - The most common blood flow test used today is a nuclear blood flow test. In this test, a mildly radioactive tracer is injected into the bloodstream (usually a vein). Measurements of radioactivity are taken, again to see if any tracer enters the brain. This test may be less accurate than the angiogram because very slow blood flow to the brain might be missed. However, brain cells, highly sensitive to oxygen deprivation, would have trouble staying alive if supplied with only that very small blood flow, so the significance of that small blood flow is probably negligible as far as brain function is concerned.
- C. Transcranial Doppler (TCD)- In this test, an ultrasound wave is sent-through the skull to measure the amount and direction of blood-flow in the arteries inside the skull. Sometimes it is difficult to find the exact area on the skull to place the sensors and in some patients with thick skulls (no joke) the TCD sensors won’t be effective. However, when done properly, the TCD can show an absence of blood flow in the arteries supplying blood to the brain.
Question: How is whole brain death determined?
Answer: The findings on examination in whole brain death are the same as in brain-stem death (no breathing, no reflexes, deep coma, etc.). The only difference is that the confirmatory studies (EEG, blood flow, etc.) show that there is no function or blood flow to any part of the brain.
What do autopsy of dead patients by neurological criteria show?
Answer: Examinations (at autopsy) of the brains of patients who have been declared brain-dead, even whole-brain-dead, do not always show that every single brain cell was dead. This does not mean that the brain was capable of functioning or that those cells were capable of function. Even people declared dead based on cardiac criteria, show evidence of cellular life in the cells of the heart for a short time even after the beating of the heart has stopped. This does not mean the heart or the person was “alive.”
Question: Can any doctor declare a patient to be brain dead?
Answer: Criteria differ from state to state, and hospital to hospital. Although any physician can legally make this declaration, it is best done by a Neurologist or Neurosurgeon or by a physician who is very familiar with the protocols and proper means of testing, in order ensure that a patient who appears brain dead is actually brain dead.
Question: What is the difference between coma and brain-death? (Are all patients in a coma also brain dead?)
Answer: Brain death is quite rare. Patients can be in a coma or have severe brain damage but still have some brain function and not brain dead. Most patients in a coma are not brain dead, and they sometimes recover. Patients who are brain dead (whole brain dead and brain-stem dead), on the other hand, have no chance of recovery.
Question: What is persistent vegetative state (PVS)?
Answer: PVS is a type of coma. A PVS patient is not dead according to American law or Israeli law. PVS describes severe brain damage where the patient is unconscious and does not respond significantly to most stimulation. The unconscious patient sometimes responds to some pain and has some reflexes, but does not respond to voice and does not communicate. Most often PVS patients are breathing on their own. The diagnosis of PVS is given only after this medical situation has persisted for a period of months.
There have been rare cases where PVS patients have regained consciousness. Persistent vegetative state differs from whole brain-death in that patients who are brain dead have absolutely no observable function or reflexes of the do not breathe autonomously, and have no chance of recovery.
Question: Will doctors refrain from administering full medical care if they know a patient has a signed organ donor card?
Answer: Some people believe that if doctors know you have a donor card they will prematurely declare you dead before you really are dead in order to get your organs. First, it is difficult to imagine that a doctor in good conscience would kill one patient in order to save another. Such action is unethical and illegal, exposing the physician and the hospital to criminal and civil liability. Second, most hospitals have established protocol that demands a separate medical team – a team that was not taking care of the patient and is unaware that the patient is a potential donor – to determine if the patient is brain-stem dead or not.
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