Brain death is the permanent and irreversible loss of brain function, which could also mean the cessation of an individual's involuntary survival mechanisms. It's not the same as a persistent vegetative state, in which the person is aware and some of their body's processes still work. It is not the same as locked-in syndrome and is not like a coma because some brain and body movement and function still goes on. Using a differential diagnosis, doctors can tell the difference between all these diseases.
Brain death is used as a sign of formal death in many places, but the public has different ideas about what it means. Different parts of the brain can keep working even after others have stopped, and the word "brain death" has been used to describe a wide range of situations. One major medical reference says that "brain death" is the same as "cerebral death," which is the death of the brain. However, the US National Library of Medicine's Medical Subject Headings (MeSH) system says that "brain death" includes the brainstem. For example, a person with a dead cerebrum but a functioning brainstem may still be able to breathe on their own, whereas in whole-brain death, which includes brainstem death, only life support equipment would be able to maintain breathing. In some countries, organs from people who are brain-dead can be taken out during surgery and given to people who need them.
Background in Medical Law
In medical law and medical jurisprudence, there are clear repercussions when operational definitions of death are different. In both the legal and medical worlds, death has usually been defined as the permanent end of different biological processes, like breathing and heartbeat. As doctors became better at reviving people who were not breathing, had no heartbeat, or showed no other signs of life, they needed a new way to define death, which led to problems in the law. This is more important now that life support equipment is used more often and that organ transplants are possible and needed more often.
Since the 1960s, all countries with organ transplantation schemes have had rules about how to decide if someone is dead. In 1971, Finland was the first European country to use brain death as a legal meaning (or sign) of death. In the United States, however, Kansas had already passed a similar law before Finland.
In 1968, an ad hoc group at Harvard Medical School put out a study that set the standard for what a permanent coma is. The Harvard criterion was finally used to define what is now called "brain death." In the United States, state lawmakers started to accept brain death as a sign of death after the case of Karen Ann Quinlan in 1976. Defining Death: Medical, Legal, and Ethical Issues in the Determination of Death, published in 1981 by a presidential commission, rejected the "higher-brain" theory of death in favour of a "whole-brain" definition. The Uniform Determination of Death Act, which has now been put into place in 39 states, was based on this study. In the United States, "brain death" is used as a legal definition of death by both the legal and medical groups. This means that a person can be declared legally dead even if life support technology keeps the body's metabolic processes going.
In 1995, the Royal College of Physicians in the United Kingdom put out a report in which they said they no longer believed that the tests released in 1976 were enough to determine brain death. Instead, they proposed a new meaning of death based on the loss of brain-stem function for good. This new definition, which is the irreversible loss of consciousness and the inability to breathe on one's own, and the tests used to determine this state in 1976, which are almost the same, have been used as the basis for certifying death for organ transplants in successive Codes of Practise. In a clinical environment where these findings are irreversible, the Australia and New Zealand Intensive Care Society (ANZICS) states that "determining brain death requires an unresponsive coma, the absence of brain-stem reflexes, and the absence of respiratory centre function." There must be clear clinical or neuroimaging signs of acute brain pathology (such as traumatic brain injury, intracranial haemorrhage, or hypoxic encephalopathy) that is consistent with irreversible loss of neurological function." Brazil's Federal Council of Medicine updated its regulations in 2017 to include "a requirement that the patient meet specific physiological prerequisites and that the physician provide the patient with optimal care before starting procedures for diagnosing brain death and performing complementary tests, as well as the need for specific training for physicians who make this diagnosis."
The World Brain Death Project, an international group of experts, released a guideline in 2020 that: offers recommendations for the minimum clinical standards for determining brain death/death by neurologic criteria (BD/DNC) in adults and children, with clear instructions for various clinical situation.
Natural moves can happen in a brain-dead person whose organs are being kept alive by life support. This is known as the Lazarus sign or the Lazarus reflex. These moves are caused by living cells, but they are not from the brain or brain stem. Instead, these cells come from the spinal cord. Sometimes these body moves give family members false hope.
A brain-dead person shows no signs of brain function when they are physically examined. This means that they don't react to pain and don't have any cranial nerve reactions. Reflexes include a set pupillary response, an oculocephalic response, a corneal response, no response to the caloric reflex test, and no breathing on its own.
Brain death can be hard to tell apart from other medical conditions, such as an overdose of barbiturates, acute alcohol poisoning, an excess of sedatives, hypothermia, low blood sugar, a coma, or a long-term vegetative state. Some people who are in a coma can get back to their pre-coma level of functioning or close to it, and some people with severe, irreversible neurological dysfunction will still be able to breathe on their own, even though their cortex and brain stem are no longer working. The same is true of anencephaly.
Electrical activity in the brain can stop totally or drop so low that most tools can't pick it up. So, an EEG will be flat, though this can also happen during heavy anaesthesia or when the heart stops beating. A flat EEG test is still used to confirm death in the United States even though it is not required to do so. It is not regarded as helpful in the UK since the Code of Practise states that whatever persistent activity it may reveal in brain regions above the brain stem is not significant for the diagnosis of death.
To be sure that brain death is permanent, it is often necessary to be very careful when diagnosing it. Various laws have varying standards, but two different doctors must examine your brain. A total and irreversible loss of brain function-referred to as brain stem function in the UK-must be evident from the tests. They could consist of two isoelectric (flat line) EEGs obtained 24 hours apart (or fewer in other countries where it is understood that there is no need to wait that long to verify irreversibility if the malfunction is caused by a clear physical trauma). If the diagnosis is based on EEG factors, the patient should have a normal temperature and not be taking any drugs that can slow down brain activity.
Additionally, additional testing must be considered when a radionuclide cerebral blood flow scan reveals no intracranial blood flow. A patient's test results could be falsely positive due to temporary brain enlargement, especially in the first 72 hours, even if they might improve better with additional time.
CT angiography is neither needed nor enough to figure out what's wrong.
Confirmatory tests are only needed for children younger than 1 year old. Children and adults can choose whether to be tested. Other cases where confirmatory testing might be needed include severe facial trauma that makes it hard to find brainstem reflexes, abnormalities in the pupils that were already there, and patients with severe sleep apnea and/or lung disease. Tests that can be used to support a diagnosis include cerebral angiography, electroencephalography, transcranial Doppler ultrasound, and cerebral scintigraphy (technetium Tc 99m exametazime). Cerebral angiography is thought to be the most accurate way to prove that a person has died from brain damage.
Even though a diagnosis of brain death is now used as proof of death for legal reasons, it is very different from biological death, which is what everyone knows and agrees is death. If mechanical ventilation and other life-support measures are kept up after a person is declared brain dead, their important organs will continue to work. This gives the best chance for their transplantation.
When mechanical ventilation is used to keep an organ donor's body alive until it can be transplanted into another person, the date that brain death was discovered is recorded as the donor's date of death.
Everyone who satisfies the legal definition of death is automatically an organ donor in various nations, including Spain, Finland, Wales, Portugal, and France. However, people can choose to opt out of the system in Singapore, Spain, Wales, France, the Czech Republic, Poland, and Portugal. In other places, organ giving may need permission from a family member or next-of-kin. When applying to be a driver in New Zealand, Australia, the UK (except for Wales), and most U.S. states, people are asked if they want to be listed as organ donors.
In the United States, if a patient is about to die or is already dead, the doctor must tell an Organ Procurement Organisation (OPO) and keep the patient alive while the patient is checked to see if they are a good donor. The OPO looks to see if the person who died was registered as a donor, which is legal consent. The OPO will request authorization from the next of kin if the deceased person wasn't registered as a donor or didn't provide it in another manner (such as on a driver's licence). The patient is kept alive with the help of a ventilator until the organs have been taken out carefully. Some important organs, such as the heart and lungs, may not be able to be saved if the patient has said in an advance health care directive that they do not want artificial ventilation or a do-not-resuscitate (DNR) order and that they want to donate their organs.
Brain death is the cause of 2% of all hospital deaths in adults and 5% of all hospital deaths in children in the United States. In 2019, a national survey of paediatric intensive care units (PICUs) in the United States found that more than 3,000 of the 15,344 children who died in PICUs had died from brain problems. "Brain death evaluations are not done often, even in large PICUs," says a national study.