Brain Death

What is Brain Death?

Death in the United States is determined by the Uniform Determination of Death Act (UDDA), which was proposed in 1981. According to this act, a person is declared dead under two main conditions:

1. If the heart and lungs have stopped working in an irreversible way.
2. If the entire brain, including the brainstem (a part of the brain responsible for fundamental life functions), has irreversibly stopped functioning.

This act was introduced in response to new medical advancements in life support technology in the 1970s that allowed doctors to keep patients’ hearts and lungs functioning even if their brains had completely stopped working.

The UDDA, however, was not clear on what medical standards should be used to determine these conditions. In response, the American Academy of Neurology (AAN) set the initial standards in 1995 and updated them in 2010.

In their most recent guidance, the AAN explains that death from brain failure means there has been a complete loss of consciousness (coma), brainstem reflexes (basic responses to stimuli), and the natural ability to breathe. This must be irreversible–meaning, no medical treatment can help recover these functions. Even the use of sophisticated life support machines, which can keep a person’s heart and lungs working, does not change this definition of death.

In 2012, the World Health Organization (WHO) and an international forum agreed to make brain death the official diagnosis of death. However, the criteria for brain death can vary globally and even within the different states of the United States. This includes differences based on the age of the patient. Therefore, health providers must be aware of the specific criteria applicable to each patient under their care.

It’s important to explain the difference between the terms ‘brain death’ and ‘coma’ to the public. ‘Coma’ can suggest a minimal level of life, whereas ‘brain death’ is equivalent to being dead. Knowing this difference can help doctors and families of patients make informed decisions about stopping medical treatment and can prevent the unnecessary use of resources.

This definition of death also affects organ transplants. Under the “dead donor rule,” organs can only be taken from a person for transplantation after they have been officially declared dead. This means that if a person’s brain has stopped working (they are brain dead), their organs can be used for transplantation, even if their heart and lungs are still working. This rule can stir up debate and controversy.

Finally, it’s also important to distinguish brain death from other severe brain conditions, like vegetative state and minimally responsive state. In these conditions, some parts of the brain still function, and there is a slight chance of recovery, especially in patients who have suffered traumatic brain injuries.

What Causes Brain Death?

Brain death is when the brain is severely damaged due to a sudden and severe injury. This can happen when the pressure inside the skull is too high, causing a decrease in blood flow to the brain. To put it simply, brain death occurs when the pressure inside the skull is greater than the pressure created by the heart to pump blood. This can cause lack of oxygen in the brain tissues, leading to damage.

This condition could be from two types of causes:

Inner skull causes: In adults, the most common causes of such severe injuries that lead to brain death include traumatic brain injuries and bleeding in the brain. These events increase the pressure inside the skull, decrease blood flow to the brain, and reduce the oxygen reaching the brain tissues, which can result in damage to the nerve cells. In children, severe head injuries caused by accidents can also lead to a similar increase in pressure and subsequent damage.

Causes outside the skull: In both adults and children, a critical cause of brain death that originates outside the skull is when the heart and lungs stop working, and help doesn’t arrive soon enough. This situation leads to a prolonged stop of blood flow to the brain, causing a lack of oxygen, breakdown of the cell’s essential functions, and severe brain swelling. Because the skull is a confined space, this increased pressure then leads to even less blood flow to the brain, causing more nerve cell injury.

Risk Factors and Frequency for Brain Death

Brain death is most commonly caused by four things: cardiopulmonary arrest, traumatic brain injury (TBI), subarachnoid hemorrhage, and intracerebral hemorrhage, listed here in order of how often they happen. When someone has a heart or lung failure (cardiopulmonary arrest), there is a 8.9% chance that they could become brain dead after they are revived. Those with TBI, the chance of becoming brain dead is between 2.8% to 6.1%.

• For those with a subarachnoid hemorrhage (bleeding in the space between the brain and the tissue covering the brain), the rate is 8.5% to 10.7%.
• Those with an intracerebral hemorrhage (bleeding within the brain itself), the rate is 6.1% to 9.6%.

It’s also important to note that by definition, brain death always results in death.

Signs and Symptoms of Brain Death

When deciding to determine if a person is brain dead, three conditions must be confirmed: coma, lack of brainstem reflexes, and absence of breathing.

The coma is checked by ensuring the person doesn’t respond to harmful stimuli. They shouldn’t have any reflexive eye or muscle movement. Though certain reflex movements related to the spine might still occur despite brain death. Usually, doctors use scans like an MRI, medical history, physical exams, or lab tests to determine the cause of the coma.

For brainstem (and related cranial nerve) reflex tests, each of the following reflexes must be absent for brain death to be declared:

• Pupillary light reflex (related to cranial nerves II and III): Pupils should be fixed, mid-size/dilated (4-9 mm), and not reactive to light. They might use a magnifying glass or special device to check this if results are unclear.
• Oculovestibular reflex (controlled by cranial nerves III, VI, VIII): This reflex can be tested with head movement or with a procedure that involves pouring cold water in the ear. In brain death, the eyes will turn in the same direction the head turns or won’t move toward the side where cold water was poured in the ear.
• Corneal reflex (controlled by cranial nerves V and VII): The corneal reflex, or blink reflex, can be checked with a cotton swab or drops of water or saline. In brain death, there would be no blinking in response to the stimulus.
• Gag reflex (related to cranial nerve IX): In brain death, a person won’t react by gagging when the back part of the throat is made touchy.
• Cough reflex (controlled by cranial nerve X): In brain death, a person won’t cough or react when their windpipe is suctioned.

Testing for Brain Death

Before doctors can diagnose a patient with brain death, there are several conditions that must be met. Here are some of them:

Firstly, the cause of the coma should be known and other potential causes such as severe metabolic diseases, endocrine disorders, and imbalances in the body’s acid-base status should be ruled out. If drug intoxication is suspected, doctors need to wait long enough (around five drug half-lives) for the drug to be cleared by the body, taking into account any kidney or liver dysfunction that could slow this process down.

Secondly, the patient’s core body temperature must be over 36°C and their systolic blood pressure (the pressure exerted when the heart beats) must be over 100 mm Hg. If it’s lower than this, blood pressure-boosting medicines may be given. Also, tests checking for brainstem reflexes (our responses to certain stimuli, like blinking when something rapidly approaches your eye) are needed. This is usually done by one supervising doctor, although some places might require two doctor’s examinations.

If these conditions are met, and there’s an identified cause of coma and complete lack of brainstem reflex, the doctor may proceed with apnea testing. Apnea testing checks if the patient spontaneously attempts to breathe when their oxygen levels go down. It’s usually done at the end, mostly to prevent brain swelling, which can lead to worsening conditions, from the raised carbon dioxide levels that come about during the test.

The procedure for apnea testing includes maintaining blood pressure, giving a high concentration of oxygen for at least 10 minutes, adjusting the breaths given by the ventilator, getting a baseline blood test, looking for signs of breathing for about 8 to 10 minutes and finally, repeating the blood gas tests if no involuntary breathing is observed.

If no involuntary breathing is observed and particular levels of carbon dioxide are detected in the blood, the apnea test result is positive, which would support a diagnosis of brain death.

If during the test, movements indicating breathing are seen, if the blood pressure drops, or if oxygen levels drop too low, then the test must be stopped. Also, the test may have to be retried using a specific device (T-piece) that maintains airway pressure, with administration of oxygen at particular levels.

While not always needed, hospitals often have additional tests available to confirm the diagnosis of brain death. These extra tests come in handy if the apnea test wasn’t clear enough or if the patient’s health is too fragile to undergo the apnea test. They include:

Cerebral angiography: This test involves using a special dye and X-rays to see how blood flows through the brain. This test can confirm brain death because it can show if blood flow to the brain has stopped. Limitations of this test include its invasiveness and the fact that taking the patient to the appropriate place for the test (the radiology suite) puts additional stress on the patient’s body. Also, the contrast medium (the dye used in the test) could potentially cause kidney damage, affecting the viability of the kidney for transplant. This test could potentially give false negatives if the pressure in the skull has been lowered by surgery or ventricular shunts—these are tubes used to relieve pressure on the brain by draining away excess cerebrospinal fluid.

Transcranial ultrasound: This test uses sound waves to create images of the brain’s blood vessels and can confirm brain death by showing weakened or absent blood flow signals. Limitations include the need for a skilled examiner, difficulty getting a clear image due to thick skull bones, and lowered brain pressure affecting the results.

Radionuclide brain imaging: This test involves using small amounts of radioactive materials called radiopharmaceuticals and a special camera to produce pictures of the brain. The test becomes positive for brain death when there’s an absence of tracer in cerebral circulation (the hollow skull phenomenon). The test could potentially give false results if images are not taken from more than one viewing angle.

Somatosensory evoked potentials (SSEPs): These tests measure the nerve signals generated when the nerves are stimulated. In patients with brain death, SSEPs are absent due to the brain’s lack of response to stimulation. The test results provide supportive data for EEG findings and are less likely to be influenced by drug intoxication. However, they can still be affected by very low body temperature conditions.

All these tests and observations help doctors reach a well-supported diagnosis of brain death—a very severe condition where the brain has stopped functioning completely.

Treatment Options for Brain Death

When doctors diagnose someone with brain death, it means that the person is considered legally and medically dead. This diagnosis is made following specific tests. After this, there are generally two main approaches the medical team can take, depending on the wishes of the family and the previously expressed preferences of the patient.

One option after this diagnosis is to switch off the machines that are helping the patient’s heart and lungs to function, also known as cardiopulmonary support. The other option is to prepare for the process of organ donation, if the patient or their family has given consent.

It’s essential that every step taken to diagnose brain death is recorded in the patient’s medical record. Including even the smallest details ensures that doctors have followed all the necessary steps in the diagnosis process. To make this easier, doctors often use a type of checklist, which helps to make sure they complete each step in the diagnosis of brain death.

What else can Brain Death be?

Brain death can sometimes be confused with other conditions. These can include:

• Vegetative state
• Minimally responsive state
• Locked-in syndrome
• Low body temperature (hypothermia)
• Being affected by drugs (drug intoxication)
• Guillan-Barre syndrome, a condition that affects the nerves
• Delayed paralytic clearance, a recovery condition after paralysis

Medical professionals must thoroughly evaluate a patient to rule out these other conditions before concluding that a patient is brain dead. It’s extremely important to be certain of the difference between a coma and actual brain death. When physicians follow the guidelines set out by the American Academy of Neurology, there is virtually no chance of misdiagnosing brain death.

What to expect with Brain Death

Simply put, “brain death” means the brain has stopped working and won’t start again. This condition, unfortunately, is always fatal, meaning that once someone is declared brain dead, recovery is not possible.

Possible Complications When Diagnosed with Brain Death

Doubts about the diagnosis of brain death usually come up when the guidelines or protocols set by the American Academy of Neurology (AAN) for identifying brain death are not properly followed. The risks attached to this are mistaking another neurological condition for brain death or mistakenly declaring a patient who is not brain dead as deceased.

Common Risks/Complications:

• Misinterpreting another neurologic condition as brain death
• Declaring a person as brain dead when they are not

Preventing Brain Death

Understanding that a loved one is brain dead can be hard for families. However, studies suggest that allowing the family to see the medical assessment of brain death can make the condition easier to comprehend. To fully accept the diagnosis, the family might need to have several discussions with more than one healthcare professional. These could include doctors, members of religious institutions, social workers or other members of the hospital staff.