What is brain death? Is it irreversible?

Brain death is one of the most relevant medical phenomena, Since this is a state that serves as a criterion to determine when a person ceases to be resurrected. Although there are exceptional cases, in general, brain death is what we commonly mean by “dead”, dryness.

In this article, we will see what are the characteristics that define this state of health.

    What is brain death?

    When we think of death, we usually think of a more or less prolonged process in which little by little our heart stops beating and our lungs stop working. The term expire for death or expressions such as the expiration of the last breath are a clear reference to this way of seeing death.

    However, we now know that it is possible that the cardiorespiratory functions stop and can still remain alive thanks to mechanical supports. However, there is another aspect that definitely reflects the death of a person as such, and the end of brain activity. We are talking about brain death.

    It is believed that a person’s brain death occurs when the complete and irreversible shutdown of all brain functions, Both by the hemispheres and by the brainstem. It is important to consider the nuances of complete and irreversible, as different types of brain damage are capable of causing similar symptoms which may be recoverable or involve only partial cessation of function. Thus, in order to diagnose brain death, it is necessary to certify that there is no possibility of recovery, and for this it is necessary to carry out verification tests and the application of highly systematized protocols.

    Brain death is usually caused by massive brain damage, especially when the brainstem is injured (Responsible for regulating aspects such as breathing and heart rate). One of the most common causes of brain death occurs when intracranial pressure passes the systolic artery, resulting in the cessation of blood flow to the brain. In this state, the blood usually loaded with oxygen and nutrients does not reach the brain and therefore stops functioning due to hypoxia.

      Diagnosis: key aspects to check

      Diagnosing brain death is not easy, And for this it is necessary to prove the non-existence of different brain functions through different protocols. Specifically, it is stipulated that at least two different specialist physicians should perform patient recognition, performing at least two physical exams and two separate EEGs over time.

      In the case of children under one year of age, the observation period is usually longer, which requires a higher level of checking and more repetitions because their brains are more immature and it costs more to perform a test. neurological examination.

      To diagnose brain death, it is essential to consider whether the subject is in conditions allowing this verification. This is why the organism must have a respiratory cardiac stability, either naturally or by artificial mechanisms, an adequate level of oxygenation in the blood. and a temperature level that reflects the absence of hypothermia (Which in itself can cause symptoms similar to brain death). In the latter aspect, the body should be at least above 32 ° C.

      too much it must be excluded that the body is in a state of intoxication due to drugs or under the effects of psychotropic drugs, because some substances can cause apparent death, and even many psycholeptic or depressant type substances can be misleading by preventing responses to different stimuli. Conditions due to metabolic problems, such as insulin coma, should also be excluded.

      Once these aspects prior to neurological analysis have been taken into account, the following aspects can be analyzed.

      1. Irreversible and reactive coma

      To be able to diagnose brain death, the subject must be in a coma due to a known cause and well established (excluding aspects such as those mentioned above of hypothermia or intoxication, for example). One of the main aspects to check is that the subject in question has no reaction to the stimulation. To verify this, the application of painful stimuli such as activation of the trigeminal nerve is used and no vegetative or motor reaction should occur.

      2. Brain activity: flat encephalogram

      Through the encephalogram bioelectric activity of the brain is measured. Thus, the fact that it appears flat indicates that no brain activity is recorded, which proves that the central nervous system has stopped acting.

      In addition to the encephalogram, many other neuroimaging techniques can be used to check brain activity, such as evoked potentials or various types of CT scans. However, it should be borne in mind that in order to get these images it is necessary to decide which algorithms to use, and depending on this the result will be different.

      3. Respiratory functions dependent on artificial elements

      One of the aspects that is checked when establishing brain death of a person is that he is not able to breathe on his own. The apnea test is used for this, Through which artificial respiration is temporarily stopped (after having previously oxygenated the blood) to observe whether the individual is breathing alone by observing the respiratory movements and measuring the partial pressure of carbon dioxide in the blood of the arteries ( PaCO2).

      If no respiratory movement is observed and the PaCO2 exceeds 60 mmHg (indicating maximum stimulation of the respiratory centers), the test is considered to give a positive result indicating the absence of breathing, reconnecting to the subject to artificial respiration.

      4. Lack of proper cardiac functions

      To check that the heart is not working on its own without mechanical assistance, the atropine test is applied, injecting the substance that gives the test its name into the bloodstream. In subjects with their own heart rate, this injection would mean an increase and acceleration of the heart rate, so no reaction is a negative indicator. In this way, it serves to obtain an effective criterion for establishing whether or not there is brain death.

      5. Absence of reflexes derived from the brainstem

      When the brain dies, the different reflexes and reactions typical of different types of stimuli cease to occur. The brainstem is the area of ​​the brain that regulates the most basic aspects and functions of life, so the reflexes that develop in this area are among the most basic, so its absence is reminiscent of existence. of brain death.

      One of the reflexes to explore is the photomotor reflexIn other words, whether or not the eye has a pupillary reaction to the light level (for example by focusing a flashlight directly on the pupil). In the event of brain death, there should be no reaction to light stimulation.

      Another reflex to consider is the cornea, in which it is observed whether there is a reaction to pain and friction by tactile stimulation through the use of gauze. Cold fluids are also introduced into the ear, which, in subjects living in the brain, would cause a reaction in the form of eye movement (oculovestibular reflex). The oculocephalic reflex is also checked, Quickly turn the patient’s head horizontally to check for eye movement

      In addition to the reflexes of the oculomotor system, the existence of reflexes linked to the nerves that govern the mouth and the digestive tract is also verified. For example, he tries to induce nausea by stimulating the palate and phalanx. The trachea is also stimulated in an attempt to elicit responses in the form cough or nausea. In either case, if it is a case of brain death, there should be no reaction.

        Confusion between brain death and other concepts

        Brain death is a concept that, while it may be easy to understand at first, is often confused with other terms. The most common of all is the concept of coma.

        Although a coma can result in the subject’s brain death and indeed for diagnosis, it is usually necessary that the patient has entered an irreversible coma, the latter is not identified with brain death.

        The patient in a coma, even if he remains unconscious and is in many cases unable to respond to stimuli, he still has some level of brain activity so he is still considered alive if he needs vital support to keep his heart pumping blood and breathing artificially. Although it is not always reversible in many cases, this possibility exists. People who come out of this condition usually do so within the first two to four weeks, but in some cases the coma can last for several decades.

        Another related aspect can be found in cloister syndrome. In this strange syndrome, the subject does not show any kind of stimulating reaction, but is nevertheless fully aware of what is going on around him. In some cases, they can even move their eyes. It is usually caused by damage to the brainstem resulting from injury, overdose or problems or a stroke.

          Contradictory cases: coming back from the dead

          As we have seen, one of the main characteristics of brain death is its irreversibility. The diagnosis is made once very rigorous, systematic and strict controls have been carried out. However, although it is not very common, some cases of people who were considered brain dead and who were subsequently resuscitated.

          The explanation for this phenomenon seems simple: although it is possible, it is extremely difficult to say that a brain is unrecoverable, as in some cases resulting from hypothermia or substance use. Thus, some people who were not yet brain dead may have been misdiagnosed.

          Some of the possible causes of this misdiagnosis they may be due to the alteration of the tests carried out due to not taking into account certain conditions of the subject (state of shock, hypothermia, drug use or metabolic disturbances) or confusion with conditions similar to brain death but not reaching it.

          It may be possible to find that the brain dies for a short time and manages to recover the patient if the reason for the cessation of functioning is reversible and the brain is reactivated, but in principle, brain death conceptually assumes that there is has irreversibility. in this state. So at least today (although it may not seem likely in the future, scientific research may find ways to restore functionality to an already dead brain if it is preserved) brain death it means the end of life as such.

          Organ donation

          Once the patient’s brain death is diagnosed, artificial life support can be disconnected. However, if the patient wanted to donate the organs or their relatives have given permission, these organs can be removed and transplanted, including organs that have been artificially maintained, such as the heart.

          In this regard, it should be borne in mind that the donation of some of them is only possible if the organ remains functioning, to be transplanted directly after death while the organ is still alive. . Therefore, it is an urgently developed process, something that partly puts pressure to determine when a person ceases to be “resurrected”.

          The relative of the absence of life

          The phenomenon of brain death not only tells us that the most important element to determine whether or not a person is alive is brain active.

          Moreover, it shows that the line between life and death is not as clear as one might think right now, and that it is a relative thing. With the right technical means, it would be possible to revive virtually anyone as long as brain tissue is not damaged and a way has been found to reactivate several relevant groups of neurons at once. Lack of a heartbeat is also not an objective sign that someone is gone not to come back, nor does it make sense.

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          • Racine, E .; Amaram, R .; Seidler, M .; Karczewska, M. and Illes, J. (2008). Media coverage of persistent vegetative state and end-of-life decision making. Neurology, 23; 71 (13): 1027-32.
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