Brains are far more complex machines than even the most sophisticated computer. We turn on our computer with a simple switch. The screen entertains us as it boots up, and we start checking our email, lingering on Facebook to catch up with friends, or reading the latest headlines. Have you ever wondered what your brain is doing in the early morning when you wake up and your automatic coffee machine is brewing the first cup of coffee?
The main part of our brain, the cerebrum, sits in our skull and is connected to our spinal cord via the small but important brain stem. The brainstem contains a small but important group of neurons known as the Reticular Activation System (RAS) that send messages to the brain not only to wake us up, but also to keep us awake. We call this process arousal – no, not the tingling sensation you feel when you kiss the man or woman of your dreams, but stimulation that keeps us awake. But just being awake is not enough.
We need an intact upper brain to perceive ourselves and our surroundings. Consciousness is a higher-level function that requires areas of the cerebrum to process the information we see and hear. A patient may have their eyes open and look awake, but if the brain is severely damaged, they can no longer perceive their surroundings. We call this a vegetative state.
People who are in a coma, on the other hand, are not awake and are not aware of themselves or their surroundings. You can talk to them, pinch them, show them pictures of their family – they will not respond. However, these patients are not brain dead.
What Does It Mean to be Brain Dead?
A brain-dead person may appear alive – they may have a heartbeat, they may look like they are breathing, their skin may still feel warm.
Brain death occurs when a person suffers an irreversible, catastrophic brain injury that results in the complete cessation of all brainstem functions. Brain death is not synonymous with coma or persistent vegetative state. A patient who is in a coma or waking coma usually still has some brainstem function (controlling breathing) and possibly other brain functions. When a person is brain dead, no part of the brain is still functioning.
Brain death is usually caused by:
- Trauma to the brain (e.g., severe head injury from a car accident, fall, or blow to the head)
- Cerebrovascular injury (e.g., stroke or aneurysm)
- Anoxia (i.e., when a patient is resuscitated after drowning or a heart attack, but not until the lack of blood flow/oxygenation to the brain has led to brain death)
- Brain tumor
There are strict criteria for brain death, and these criteria (PDF) are carefully followed before a patient is considered an organ donor or has their ventilator turned off. The patient must be in a coma and have no brainstem or pupillary reflexes. They do not breathe on their own when taken off the ventilator, and an electroencephalogram (EEG) shows a complete lack of brain activity. Although in most states only a single physician’s diagnosis is required, the patient’s family can always seek a second opinion.
How is it Decided that a Person is Brain Dead?
A doctor performs tests to make a diagnosis of brain death. These tests are based on sound and legally accepted medical guidelines. Tests include a clinical exam that shows a person has no brain reflexes and cannot breathe on their own. In some situations, more tests may be needed. You may ask your doctor to explain or show you how brain death was determined in your loved one.
The person may show spinal cord activity or reflexes, such as twitching or muscle contractions. Spinal reflexes are caused by electrical impulses that remain in the spine. These reflexes can occur even though the brain is dead.
What Happens to a Person While These Tests Are Being Done?
The person is hooked up to a machine that breathes for them, called a ventilator. This machine is needed because the brain can no longer send signals telling the body to breathe. Special medications may also be administered to maintain blood pressure and other body functions. During the brain death examination, the ventilator and medications continue to run, but they do not affect the results of the examination.
Are There Medications That Can Turn Off the Brain and Give a Wrong Diagnosis?
Certain medications such as muscle relaxants and sedatives can affect brain function. Testing can only be done if the person has low levels of these medications in their body. It may be necessary to wait until these levels have decreased. Then the doctor can accurately measure brain activity. Sometimes other tests are done to confirm brain death if certain medications are present in the body.
Once Brain Death Is Confirmed, Why Does a Person’s Heart Continue to Beat?
As long as the heart is supplied with oxygen, it can continue to work. The ventilator provides enough oxygen to keep the heart beating for several hours. Without this artificial help, the heart would stop beating.
Is It Possible That the Brain Dead Person Is in a Coma?
No. A patient who is in a coma continues to have brain activity and function. When brain death occurs, all brain function ceases and there is no chance of recovery.
Is There Anything Else That Can Be Done?
Before brain death is confirmed, everything possible is done to save a person’s life. After brain death is diagnosed, there is no chance of recovery.
What Happens When a Person is Declared Brain Dead?
Once a diagnosis of brain death is made, a person is declared dead. This is the time that should appear on the death certificate. The time of death is not when the ventilator is removed.
What is the Difference Between a Coma and Brain Death?
A coma is a deep state of unconsciousness with eyes closed, in which a person is unable to respond to people or their environment. In a coma, the patient is still alive and has some brain activity. Depending on the severity of the injury, the recovery time varies, and the coma may be temporary or permanent.
Patients in coma may have brainstem responses, spontaneous breathing, and/or motor responses that are not purposeful. Coma has three possible outcomes: brain death, regaining consciousness, or evolution to a state of chronic impaired consciousness, such as a vegetative state.
Patients in coma are not eligible for organ, eye or tissue donation.
Brain death is death. There is no longer any brain function. Brain death results from swelling of the brain; blood flow to the brain ceases, and without blood to supply oxygen to the cells, the tissue dies. It is irreversible. Once the brain tissue dies, nothing can be done to heal it.
The brain performs many functions, including thinking, movement, and all the neurological functions that allow the body to maintain blood pressure, heart rate, body temperature, hormones, breathing, etc. When a person suffers brain death, the body’s entire system suspends. One can no longer breathe, the heart stops beating, and the body can no longer function once the brain dies. Massive artificial medical interventions must be initiated to maintain organ function (e.g., ventilatory support), but these interventions are only a temporary measure.
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