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For a very long time, "death" existed when the heart stopped beating and breathing stopped. Then, machines were invented in the 1930s to allow people to get air even though they could not take themselves out. In the 1950s, machines were developed to help maintain the heart rate.
But no machine could bring an irreversibly damaged patient to the brain to function. As a result, the concept of "brain death" was introduced as an additional definition of death to supplement death by heart-lung insufficiency.
The concept of brain death, although legally adopted in the United States and in many parts of the world, remains a topic of ongoing discussion. It is often about the death of a person when the heart beats and the body is hot, even if this function is fully achieved through artificial support. Brain death is also harder to conceptualize because it is a less visible form of death. And is not it so much easier to believe what we can see?
On April 17, a study published in Nature who showed signs of activity in the pork brains after their death added more fuel to the discussion. I am a neurologist specializing in neurocritical care, whose clinical and research interests include acute brain injury and broad exposure to catastrophic brain injury and brain death. My analysis of the study is that it reinforces much of what we already know, that death is a continuum.
When pigs die, can their brains be revived?
In this study, scientists took brains from pigs slaughtered at USDA-regulated facilities and then connected them to a machine that injected a blood-like artificial food fluid into the brain four hours after their " died "and measured the activity of brain cells. . They discovered that even several hours after death, blood circulation – or artificial blood circulation – and certain brain cell functions could be restored in this experimental setting.
The conclusion was that death in the brain after the heart has stopped beating follows a prolonged process rather than occurring at a specific time, and that our brain may have a better healing capacity than what it does. we know now.
Is it new? Yes, at the scientific level – that is to say under the microscope, because such an experiment has never been performed before. But have we not known for a long time that death does not happen in the blink of an eye?
The historical accounts of decapitated bodies vividly describe decapitated bodies taking a few steps or even running.
This means that such a body was not immediately dead. And, conceivably, if such a body was connected to a blood supply and healed wounds, most people could probably imagine that it could continue to be maintained with parts or cells of the living body.
Can a head still be alive after decapitation?
Worse to imagine: could the decapitated head still be conscious for a moment? Maybe yes.
When the heart stops beating, we consider that someone has died. But once the heartbeat has stopped, we also know that sometimes the heartbeat can come back on its own. This is called autoresuscitation. In this case, a person who has appeared dead for a few minutes may not be really dead.
But the situation is different for the brain and for the heart. When there is no blood circulation in the absence of a heart that pumps it, or when there is intrinsic brain injury and that the blood can not penetrate in the blood, the situation is delicate. Brains are very sensitive to lack of oxygen and energy supply, and various types of brain damage occur. Depending on the length of time that the brain's energy fuel is absent, brain function may remain alive to varying degrees and be revived to a degree that we neuroscientists do not yet fully know. We know that brain function is severely disrupted, with a variable permanence of loss of function as a function of time during which the brain has not had energy.
The end result of the functional capacity of such a damaged brain is one of the biggest challenges.
After an injury, a complete sequence of consecutive processes occurs, called secondary brain injury and triggered first by the insult of the brain. And these processes often cause considerable damage, sometimes more than the first real injury.
For example, a hard blow to the head can cause bruising or bleeding in the brain, which can be removed surgically in some cases. Despite stopping or eliminating bleeding, the surrounding brain will sometimes begin to swell and injure itself even more during the following days, such as a large bruise in the thighs passing through stadiums and changing color. There is no preventive treatment yet, but we know that certain factors can make this process worse, such as low blood pressure or lack of oxygen in the brain during the healing phase.
Imagine a broken bone: melting is only the first step and there will be swelling, pain and weakness for weeks. In the brain, the process is more granular. And in neuroscience, we are just beginning to understand this cascade of events.
What to learn from the study on pork
The study of resuscitated pork brain cells does not even address this much larger picture. It is limited to showing that the duration and spectrum of nerve cell function that can persist and be at least partially restored are longer than those shown until now. Therefore, he supports the idea that death is a process and adds additional data on the duration of this process.
But this does not show that these brain cells were able to function as a network of nerve cells leading to higher brain functions such as consciousness or consciousness – the characteristics that distinguish us as human beings. It also looks at the immediate restoration of cell function, and not how these brains manage, when the ongoing process of secondary brain injury sets in.
To sum up, in the absence of blood flow, the brain, including all its individual cells, will die – eventually. And this study may have broadened the understanding of "finally".
Death is a process and not a moment. It is the human desire to classify things in black and white and to have definitions that allow us to function in everyday life. Death – it's becoming increasingly clear – is a big gray area, and we'll have to expect this gray area to grow as science progresses.
Katharina Busl, Associate Professor of Neurology. Chief, Division of Neurocritical Care, Department of Neurology, University of Florida.
This article first appeared on The Conversation.
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