Brain death: causes, development, criteria and statement

Brain death means a complete and irreversible cessation of its vital activity, when the heart continues to beat and breathing is maintained through artificial ventilation (ALV).

Unfortunately, the number of patients who have irreversible events in the brain is large. Their treatment is carried out by resuscitation specialists, ensuring the maintenance of the main life support systems - breathing and circulation. From a medical and ethical point of view, it is always difficult to establish the fact of irreversibility of brain death, because this means declaring a person dead, although his heart continues to contract.

The brain lives after a person’s death for about five minutes, that is, after cardiac arrest, it is still able to maintain its activity for some time. During this period, it is very important to have time to carry out resuscitation, then there will be a chance for a full life. Otherwise, irreversible neuronal death will be fatal.

For relatives and friends, the issue of recognizing a sick relative as non-viable due to brain death is very difficult: many believe that a miracle will happen, others believe that doctors are not making enough efforts to “revive” the patient.

There are frequent cases of litigation and disputes when relatives consider the disconnection of the ventilator to be premature or erroneous. All these circumstances force us to objectify the data of symptoms, neurological and other types of examinations, so that an error is excluded, and the doctor who turned off the ventilator does not act as an executioner.

In Russia and most other countries, brain death is identified with the death of the whole organism, when maintaining the vital functions of other organs through medication and hardware treatment is impractical, which distinguishes brain death from a vegetative state and coma.

As already mentioned, under normal conditions, brain death occurs 5 minutes after breathing and heartbeat stop, but at low temperatures and various diseases this period can be lengthened or shortened. In addition, resuscitation measures and treatment can restore cardiac activity and provide ventilation of the lungs, but brain function cannot always be returned to its original state - comas, a vegetative state, or irreversible death of nervous tissue are possible, requiring different approaches from specialists.

Brain death established through clear criteria is the only reason when a doctor has the right to turn off all life support devices without the risk of being held legally liable. It is clear that such a formulation of the question requires compliance with all diagnostic algorithms for this condition, and an error is unacceptable.

Stages of diagnosing brain death

To accurately determine whether the brain is alive or whether irreversible and incompatible changes have already occurred in it, clear recommendations have been developed that should be followed by every specialist who encounters a patient in serious condition.

Diagnosis of brain death includes several stages:

Accurate determination of the cause of the pathology.
Exclusion of other brain changes that are clinically similar to his death, but under certain conditions can be reversible.
Establishing the fact of cessation of activity of the entire brain, and not just its individual structures.
Accurate determination of irreversibility of brain damage.

Based on clinical data, a doctor has the right to make a diagnosis of brain death without using additional instrumental diagnostic methods, since the developed criteria make it possible to determine the pathology with absolute accuracy. However, in our time, when the conclusion about any disease is based on a variety of objective results, instrumental and laboratory tests are involved in the diagnostic process.

brain perfusion on MRI is normal (left), with brain death (center), with a vegetative state (right)

Additional examinations are not excluded from diagnostic algorithms for brain death, but are not strictly required. Their purpose is to speed up the establishment of the fact of brain death, especially in clinically complex cases, although it is quite possible to do without them. In Russia, only electroencephalography and angiography of the carotid and vertebral arteries are allowed as the only reliable ones in determining signs of irreversibility of brain disorders.

Forecasts

Clinical death does not always mean that the patient will definitely die. Sometimes doctors manage to bring a person out of a state of clinical death. The prognosis will be influenced by what circumstance led to such a condition and what resuscitation measures were taken. The main condition is to restore blood circulation in the first 3-5 minutes. Sometimes resuscitation is carried out for up to 20-40 minutes.

Even if partial extinction and death of neurons has occurred, the functions of the medulla can be restored. If biological death or brain death is established, it is impossible to bring the patient back to life, you need to come to terms with this.

The peculiarity of the human brain is that it strives to preserve its functions by any means. If some neurons die, their tasks can be redistributed to other zones. Patients who have suffered a stroke, ischemia, and even serious TBI often return to a full life.

Features and criteria for declaring brain death

In medicine, the concepts of clinical and biological death refer to the entire body, implying the reversibility or irreversibility of changes occurring. Applying this parameter to nervous tissue, we can speak of clinical brain death in the first 5 minutes after breathing stops, although the death of cortical neurons begins already in the third minute. Biological death characterizes a total disorder of brain activity that cannot be reversed by any resuscitation or treatment.

The need to assess the state of the brain usually arises in comatose and similar conditions, when the patient is unconscious, contact with him is impossible, hemodynamics and heart function may be unstable, breathing is usually supported by a device, the pelvic organs are not controlled, there is no movement and sensitivity, reflexes and muscle tone fades away.

Reanimation

The consequences of brain death are irreversible. Just because a person is unconscious does not mean that he needs to perform resuscitation measures (ventilation, cardiac massage).

Cardiac massage is strictly contraindicated if the victim’s heart is beating, even abnormally. In this case, massage can, on the contrary, interfere with the correct contraction of the heart muscles.

Mouth-to-mouth or mouth-to-nose breathing, as well as chest compressions, are performed only if there is no heartbeat. Such events can save a person's life. If you ensure the supply of oxygen to the body and improve blood circulation, irreversible necrotic changes will not occur. Body functions can be completely restored.

If a pregnant woman is injured, it is important to monitor not only her vital signs, but also the condition of the fetus. The patient must be taken to the hospital as quickly as possible, since the child may die due to injury and stress.

It is extremely important to thoroughly master resuscitation techniques. Any of us can master them and, if necessary, save a person’s life.

Assessment of causes of brain death

A doctor has the right to begin diagnosing biological brain death only when the causative factors and mechanisms of changes in nervous tissue are precisely known. The causes of irreversible brain disorders can be primary, caused by direct damage to the organ, and secondary.

Primary brain damage leading to brain death is provoked by:

Severe traumatic brain injuries;
Hemorrhages, both traumatic and spontaneous;
Cerebral infarctions of any nature (atherosclerosis, thromboembolism);
Oncological diseases;
Acute hydrocephalus, edema;
Previous surgical operations inside the skull.

Secondary irreversible damage occurs due to pathology of other organs and systems - cardiac arrest, shock, severe hypoxia against the background of systemic circulatory disorders, severe infectious processes, etc.

An important diagnostic step is the exclusion of all other pathological conditions that could manifest symptoms similar to brain death, but which, nevertheless, are potentially reversible with proper treatment. Thus, the diagnosis of brain death should not even be assumed until a specialist makes sure that there are no influences such as:

Intoxication, drug poisoning;
Hypothermia;
Hypovolemic shock due to blood loss, dehydration;
Coma of any origin;
The effect of muscle relaxants, anesthetics.

In other words, an indispensable condition when diagnosing brain death will be the search for evidence that the symptoms are not caused by drugs that depress the nervous tissue, poisoning, metabolic disorders, or infections. In case of intoxication, appropriate treatment is carried out, but until its signs are eliminated, a conclusion about brain death is not considered. If all possible causes for the lack of brain functioning are excluded, then the question of its death will be raised.

When monitoring patients with brain disorders potentially associated with other causes, the rectal temperature is determined, which should not be less than 32 C, the systolic blood pressure is not less than 90 mm Hg. Art., and if it is lower, vasopressors are administered intravenously to maintain hemodynamics.

Symptoms of brain diseases

The most common brain diseases include atherosclerosis, stroke, tumor, vascular aneurysm, and Alzheimer's disease. According to statistics, up to 85% of people are predisposed to developing diseases related to the blood supply to the brain. Such data are a consequence of the unhealthy lifestyle of modern man. The danger of brain diseases lies in their asymptomatic nature. That is, for a long time they do not make themselves felt.

Common symptoms of brain diseases include:

Frequent headaches that do not go away even after taking medications.
Memory impairment.
Constant fatigue.
Fainting.
Cramps.
Fever. Body temperature can reach up to 40 degrees.
Weight loss to the point of exhaustion.

Specific symptoms of atherosclerosis:

Noise in ears. It occurs when a cholesterol plaque has blocked 60% of the blood flow in an artery.
Decreased erection. If a man under 50 years of age has decreased erection, then such a patient's risk of dying from a myocardial infarction is many times higher than that of the same person with normal erectile function.
Coldness in the extremities. The vessels become stiffer and blood flows through them worse.

Specific symptoms of stroke:

Numbness of the face and limbs.
Double vision.
Difficulty moving.

Every third death in Russia is associated with this pathology.

Stroke happens:

Ischemic. Associated with blockage of arteries, cessation of blood flow to the brain and necrosis of its tissue. The cause of the appearance is blockage of blood vessels leading to the brain due to atherosclerotic plaque. The second reason is the occurrence of a blood clot in the heart when it is not working properly (for example, during an arrhythmia). As a result, the blood clot “runs” into the brain vessels, causing thrombosis.
Neurological. Associated with hemorrhage and hematoma formation inside the skull. It occurs due to high blood pressure when, at its peak, a small vessel inside the brain ruptures and a hematoma appears.

There are signs of a stroke that, if recognized in time, can save a life. To make it easier to memorize, they can be combined into the word “IMPACT”:

Smile. If a person cannot smile and one of the corners of his mouth is drooping.
Movement. A person cannot move both arms or legs at once.
Articulation. A person cannot say anything clearly, not even his name.
Solution. To save a person, you should take him to the hospital and carry out the necessary examinations within 1-2 hours.

Specific symptoms of Alzheimer's disease:

Avoiding contact with people.
Lost in space.
Decreased emotionality and interest in life.
Hallucinations.

Alzheimer's disease is a form of dementia that occurs in older people. It is most often found in patients who have crossed the threshold of 65 years. At the moment it is incurable.

Specific symptoms of a brain tumor:

The headache does not go away within two weeks to a month.
Headache is accompanied by vomiting, hearing loss and coordination.
Motor perseverations (inability to stop performing an action).
Inattentiveness and forgetfulness progresses.

Brain tumors are divided into benign, malignant and metastases. In the case of benign, the disease develops gradually, slowly and gently over several years.

Types of brain tumors:

Intracerebral. The most common and aggressive form is glioblastoma. It is almost impossible to defeat her. The tumor grows through healthy tissue and cannot be localized.
Extracerebral. They grow on the base or surface of the skull.
Metastases are secondary brain tumors. The main cancer cells penetrate the bloodstream into the brain and cause the growth of metastases.

Clinical data analysis

The next stage in diagnosing brain death, which begins after establishing the causes and excluding other pathologies, will be the assessment of clinical data - coma, absence of brainstem reflexes, inability to spontaneously breathe (apnea).

Coma is a complete absence of consciousness. According to modern concepts, it is always accompanied by total atony of the muscular system. In a coma, the patient does not react to external stimuli, does not feel pain, changes in the temperature of surrounding objects, or touch.

Brainstem reflexes are determined in all patients without exception with possible brain death, while the following signs are always taken into account to verify the diagnosis:

There is no response to sufficiently intense pain effects in the areas of exit of the branches of the trigeminal nerve or the absence of other reflexes, the arcs of which close above the cervical part of the spinal cord;
The eyes do not move, the pupils do not react to a light stimulus (when it is clearly established that there is no effect of medications that dilate them);
Corneal, oculovestibular, tracheal, pharyngeal and oculocephalic reflexes are not detected.

The absence of oculocephalic reflexes is determined by turning the patient's head to the sides with raised eyelids: if the eyes remain motionless, then there are no reflexes. This symptom is not assessed for cervical spine injuries.

checking oculocephalic reflexes

connection of oculocephalic and oculovestibular reflexes with brain stem vitality

To determine oculovestibular reflexes, the patient's head is raised, and cold water is pumped into the ear canals using a thin catheter. If the brain stem is active, the eyeballs will deviate to the sides. This symptom is not indicative of injury to the eardrums with a violation of their integrity. Pharyngeal and tracheal reflexes are checked by displacing the endotracheal tube or inserting a bronchial suction catheter.

One of the most important diagnostic criteria for brain death is the inability to breathe independently (apnea). This indicator is the final one at the stage of clinical assessment of brain functioning and can be determined only after checking all of the above parameters.

To determine whether a patient is able to breathe on his own or not, it is unacceptable to simply disconnect him from the ventilator equipment, since sudden hypoxia will have a detrimental effect on the already suffering brain and myocardium. Disconnection from the equipment is carried out on the basis of an apneic oxygenation test.

An apneic test involves monitoring the gas composition of the blood (the concentration of oxygen and carbon dioxide in it), for which a catheter is installed in the peripheral arteries. Before disconnecting the ventilator, ventilation of the lungs is carried out for a quarter of an hour under conditions of normal CO2 content and high oxygen pressure. After these two rules are observed, the ventilator is turned off, and humidified 100% oxygen is supplied to the trachea through the endotracheal tube.

If spontaneous breathing is possible, then an increase in the level of carbon dioxide in the blood will lead to activation of the stem nerve centers and the appearance of spontaneous respiratory movements. The presence of even minimal breathing serves as a reason to exclude brain death and immediately return to artificial ventilation of the respiratory system. A positive test result, that is, absence of breathing, will indicate irreversible death of the brain stem structures.

Characteristic symptomatic criteria

The symptoms characteristic of the respiratory brain condition are in many ways similar to the clinical picture of a very deep coma, differing from it in its complete irreversibility.

As a result, this condition is sometimes also called “extraordinary coma.” There is a complete loss of central nervous system functions (consciousness, speech, reaction to external stimuli) while maintaining cardiac activity. Blood pressure is maintained or maintained with medication.

The respiratory function is ensured by artificial ventilation of the lungs. Characterized by complete loss of skeletal muscle tone, total areflexia, hypothermia, urinary and fecal incontinence. A very typical symptom is doll eyes: when you turn your head in any direction (up, down, to the sides), your eyes involuntarily shift to the opposite side.

Observation and proof of irreversibility of pathology

In the absence of breathing, we can talk about the loss of vital activity of the entire brain; the doctor can only establish the fact that this process is completely irreversible. The irreversibility of brain disorders can be judged after a certain period of observation, depending on the cause of the pathology that caused the death of the nervous tissue.

If primary brain damage has occurred, then to establish brain death, the duration of observation must be at least 6 hours from the moment when the symptoms of the pathology were first recorded. After this period, a repeat neurological examination is performed, and the apnea test is no longer necessary.

Previously, it was recommended to observe the patient for a minimum of 12 hours, but now in most countries of the world the time has been reduced to 6 hours, since this time interval is considered sufficient to diagnose brain death. In addition, reducing observation time plays an important role when planning organ transplantation from a brain-dead patient.

In case of secondary damage to the nervous tissue, a longer observation is required to make a diagnosis of brain death - at least a day from the moment of the initial symptoms of the pathology. If there is reason to suspect poisoning, the time is increased to 72 hours, during which neurological monitoring is carried out every 2 hours. If the results are negative, brain death is declared after 72 hours.

Based on the stated diagnostic criteria, during observation of the patient, undoubted signs of brain death are recorded - the absence of reflex and brainstem activity, a positive apneic test. These parameters are considered absolutely indicative and reliable, not requiring additional examination, and therefore are used by doctors all over the world.

What is a cerebral hemorrhage

A cerebral hemorrhage is a life-threatening condition that occurs when one of the brain's arteries ruptures, causing blood to leak into the brain tissue.
The brain tissue becomes saturated with blood or a hematoma forms (an accumulation of blood that puts pressure on surrounding tissues); blood may leak into the ventricle of the brain, which disrupts the outflow of cerebrospinal fluid and increases intracranial pressure. The part of the brain that has lost blood due to rupture of blood vessels and those tissues that are saturated with blood stop working, the cells die. Accordingly, the larger the vessel that ruptures, the more dangerous the consequences will be for life and health.

Additional examinations

Of the additional examinations that may affect the diagnosis, electroencephalography (EEG) and angiography are permitted. EEG is indicated for those patients for whom it is difficult to determine reflexes - in case of injuries or suspected injuries of the cervical spinal column, ruptured eardrums. An EEG is performed after all tests, including apnea. In brain death, it shows the absence of any electrical activity in the nerve tissue. If the indicators are questionable, the study can be repeated or using stimuli (light, pain).

non-collapsed cerebral vessels are normal on angiography

If EEG is indicated in clinically complex cases and does not affect the duration of general observation, then panangiography of the carotid and vertebral arteries is designed to shorten this time as much as possible. It is carried out at the final diagnostic stage and confirms the irreversibility of the cessation of brain activity.

For example, in case of possible intoxication, the patient should be observed for at least three days, but brain death can be determined early if, immediately after the appearance of signs of loss of its functions, the main arteries of the brain are examined twice with an interval of at least half an hour. In the absence of contrasting of the arteries, we can talk about a total and irreversible stop of cerebral blood flow, and further observation becomes impractical.

Video: example of an EEG to confirm brain death

Clinical diagnosis of biological brain death is labor-intensive, requires constant monitoring and maintenance of vital functions, so for many years the search has been underway for another method that would allow us to establish a reliable diagnosis with no less accuracy than the clinic. However, no matter how hard the experts try, none of the proposed methods is comparable in accuracy and reliability to a clinical assessment of the state of the brain. Moreover, other techniques are more complex, less accessible, invasive or not specific enough, and the result is greatly influenced by the experience and knowledge of the doctor.

The desire to speed up the process of ascertaining brain death is largely due to the rapid development of a new branch of medicine - transplantology. Considering the diagnosis of brain death from this position, we can say that the price of a conclusion about brain death may be not one, but several lives - both of the potential donor and of other people in need of organ transplants, therefore haste or non-compliance with the observation algorithm is unacceptable.

When deciding to declare brain death, the doctor must remember the ethical side of the issue and the fact that the life of any person is priceless, therefore strict compliance of his actions with the established rules and instructions is mandatory. A possible mistake increases the already high degree of responsibility, forcing you to repeatedly play it safe and doubt, double-check and weigh every step.

The diagnosis of brain death is established jointly by a resuscitation specialist and a neurologist, and each of them must have at least five years of work experience. If additional examination is necessary, specialists of other profiles are involved. Transplantologists and other persons involved in the collection and transplantation of organs cannot and should not participate in or influence the process of diagnosing brain death.

How to tell your family

Recently, it has become common to resort to the help of a psychologist in such cases. It will help family members come to terms with their loss.

Making a decision to disconnect a patient from life support is extremely difficult even for experienced doctors. Relatives are always unprepared for such a tragic development of events, so they literally lose their minds. Relatives tend to believe that they can still try to do something. They are often asked to wait at least a few days. If there is accurate evidence of brain death, the doctor must find the right words to explain the current situation to the relatives.

According to the rules of bioethics, if brain death is definitely established, the patient should be disconnected from devices that support life processes. There is no point in expecting him to come back to life if all tests have confirmed the absence of neuronal activity. This will be a humane decision.

Relatives should definitely ask what diagnostic research methods were used. The doctor must show a document confirming the established brain death. Only relatives have the right to decide to disconnect the victim from life-sustaining devices. The doctor’s task is not to succumb to emotions, but to make the right decision based on the specific results of the patient’s examination.

It is important to exclude the human factor and rely only on test results.

How long to keep the victim on life support is decided individually in each case. After a person is disconnected from the devices, Lazarus syndrome may occur. It consists in the fact that the deceased experiences individual muscle twitches. The head may turn involuntarily, the person may bend an arm or leg. It even happens that an already dead person arches. This is the result of contraction of the back muscles. It is important that the doctor warns the patient’s relatives in advance that such manifestations are possible. This does not mean that the victim comes to life.

After diagnosis...

Once brain death has been confirmed by all clinical data, doctors have three options. In the first case, they can invite transplantologists to decide on the issue of organ collection for transplantation (this mechanism is regulated by the legislation of a particular country). In the second, talk to your family, explain the essence of the pathology and the irreversibility of brain damage, and then stop artificial ventilation. The third option, the most economically unprofitable and impractical, is to continue maintaining the functioning of the heart and lungs until they decompensate and the patient dies.

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The problem of brain death with intact cardiac activity is not only of a medical nature. It has a significant moral, ethical and legal aspect. Society as a whole knows that brain death is identical to the death of the patient, but doctors have to make serious efforts, tact and patience when talking with relatives, deciding on transplantation issues and determining the final option of their actions after making a diagnosis.

Unfortunately, cases of distrust in doctors, unjustified suspicions of unwillingness to continue treatment, and accusations of negligence in their duties are still common. Many people still think that with a superficial assessment of the patient’s condition, the doctor will simply turn off the ventilator without making sure that the pathology is irreversible. At the same time, delving into the diagnostic algorithms, one can imagine how long and difficult the path to the final diagnosis is.