Death of the brain

Death of the brain presupposes a persistent lack of consciousness, steady spontaneous breathing and stem reflexes; Spinal reflexes, including deep tendon reflexes, plantar flexion and limb withdrawal reflexes (flexion reflexes) may persist.

The concept of brain death arose with the advent of the ability to maintain breathing and circulation, despite the complete loss of brain activity. Therefore, the definition of a person's death as an irreversible cessation of brain activity, especially the structures of the brainstem, is widely accepted in legislation and society.

At all times there was no more exciting and mysterious problem for mankind than life, death and transitional stages between these interconnected and mutually exclusive concepts. The states bordering on being and non-being cause huge interest and cause states: lethargy, some amazing "como-like" stages of autosuggestion of Indian yogis, etc. However, at first these phenomena attracted the attention of philosophers and writers more than physicians. It seemed obvious to the doctors that a few minutes after stopping the heart and breathing life stops, death begins. Back in the VII century. Democritus wrote that in reality there are no compelling signs of death for doctors. V. Montgomery in 1896 argued that cases of erroneous burial are at least 2% during epidemics and mass battles. And the famous story of Edgar Poe "Healed buried" so impressed contemporaries that a certain Karnice in 1897 patented in Berlin a witty device for signaling to others about a possible "reviving the corpse."

Since 1927, after the creation of Paul Drinker "iron lungs," which laid the foundation for resuscitation benefits, the era of active maintenance of extinct vital functions has come. An unprecedented progress in this field of medicine is associated with the enormous success of medical technology. The use of forced synchronized breathing, defibrillation, artificial pacemakers, cardiopulmonary resuscitation, artificial circulation, controlled hypothermia, hemodialysis, hemosorption and other methods, seemed to offer unlimited possibilities for recovery and prolonged artificial maintenance of the basic human body.

In 1959, for the first time in the world, the French researcher Mollaret described 8 patients who were in the intensive care unit for IVL, who completely lacked all stem reflexes, responses to pain stimuli, and pupillary responses to light. In all patients, cardiac arrest occurred within 7 hours from the moment of fixation of the described condition, and during autopsy, pronounced necrotic changes of brain substance were detected up to the formation of detritus. The author called this state a transcendental coma.

In 1968, the Harvard criteria for the death of a person based on brain death were published. They postulated the possibility of diagnosing death, based on the cessation of brain function, and the term "brain death" was first used.

In recent decades, the specialist for the restoration of impaired functions in patients with urgent intracranial lesions (severe TBI, the rupture of extensive intracerebral aneurysm, etc.) increasingly has a very serious moral and legal responsibility - to participate in authorizing the cessation of resuscitation and the taking of organs of the deceased for transplantation. Significant successes of transplantology in artificial implantation of not only the kidney, but also the heart, liver and other organs make the problem of creating a "donor bank" extremely urgent. Severe patients of the neurological and neurosurgical profile are relatively young and somatically healthy people, according to most researchers, the optimal "candidates for donors".

The results of modern studies indicate that the pathogenesis of dying and death of the brain is extremely complicated and involves reversible and irreversible stages. Until recently, the clinical signs of brain death were considered to be a lack of response to any sensory stimulation, the absence of spontaneous breathing and any spontaneous motor phenomena, the emergence of bilateral mydriasis with no pupillary response to light, a rapid drop in blood pressure when the artificial circulation stopped. However, some researchers believe that none of these clinical criteria can be considered pathognomonic reflection of brain death. On the one hand, spinal reflexes may be present for some time after documented brain death; on the other hand, all the signs considered to be undoubted symptoms of brain death can not really be considered as such: they do not always reflect the biological death of a person.

Thus, the death of a person from the position of a doctor is not a cardiac arrest (it can be restarted and sustained again and again, saving the patient's life), non-stopping of breathing (quick transfer of the patient to forced ventilation restores gas exchange), but stopping the blood circulation of the brain. The overwhelming majority of researchers around the world believe that if the death of a person as an individual, and not as an organism, is inextricably associated with brain death, then the death of the brain is almost equivalent to stopping and non-resumption of brain perfusion.

Pathophysiological mechanisms of brain death

Severe mechanical damage to the brain most often occurs as a result of a trauma caused by a sharp acceleration with an oppositely directed vector. Such injuries most often occur in car accidents, falls from a high altitude, etc. Craniocerebral injury in these cases is due to a sharp anti-phase movement of the brain in the cranial cavity, in which direct destruction of brain areas occurs. Critical non-traumatic brain lesions occur more often as a result of hemorrhage, either to the brain substance or to the meninges. Such severe forms of hemorrhage, as parenchymal or subarachnoid, accompanied by the discharge of large amounts of blood into the cranial cavity, trigger mechanisms of brain damage similar to those of the brain injury. To fatal brain damage is also anoxia, resulting from the temporary cessation of cardiac activity.

It is shown that if the blood completely ceases to enter the cavity of the skull within 30 minutes, it causes irreversible damage to the neurons, the restoration of which becomes impossible. This situation occurs in 2 cases: with a sharp increase in intracranial pressure to the level of systolic blood pressure, with cardiac arrest and inadequate indirect cardiac massage for the specified period of time.

Pathophysiological mechanisms of brain death

Clinical criteria for brain death

For a medical opinion on brain death, it is necessary to establish the cause of organic or metabolic brain damage, to exclude the use, especially of independent, anesthetic and paralyzing drugs. It is necessary to correct hypothermia below 32 ° C and exclude epileptic status.Do studies need to be done in the course of 6-24 hours. The study should include the determination of pupillary response, oculo- vestibular and oculocephalic reflexes, corneal reflexes, and apneetic oxygenation test. Additional evidence for family members is possible, but not necessarily the use of EEG.

Cases of recovery after an adequate diagnosis of brain death are not known. Even in conditions of mechanical ventilation, after a few days usually there is an asystole. Termination of mechanical ventilation is accompanied by the development of terminal arrhythmia. During the terminal apnea spinal motor reflexes can arise: arching of the back, turning of the neck, tension of the muscles of the legs and flexion of the upper limbs (the so-called sign of Lazarus). This should be cautioned by family members who choose to be present at the end of the ventilator.

Recommendations for determining the death of the brain in persons older than one year

To establish the death of the brain, it is necessary to comply with all 9 requirements.

1. Possible attempts to notify relatives or other close people
2. The cause of coma is known and is quite capable of leading to an irreversible cessation of brain function
3. Excluded: the possibility of muscle relaxants and substances, depressing the central nervous system, hypothermia (<32 ° C) and arterial hypotension (SBP <55 mm Hg)
4. All observed movements can be carried out due to activity of the spinal cord
5. There are no cough and / or pharyngeal reflexes
6. There is no corneal reflex and the pupils' reaction to light
7. There is no reaction in the caloric sample with irrigation of the tympanic membrane by ice water through the external auditory meatus
8. The apneetic oxygenation test for a minimum of 8 min does not reveal respiratory movements against the background of the proven increase in PaCO2> 20 mmHg. Above the initial pretest level

Procedure: The test is performed by disconnecting the ventilator from the endotracheal tube, where oxygen is supplied through the cannula at a rate of 6 l / min. Passive growth of PaCO2 stimulates breathing, however, spontaneous respiratory movements do not appear during 8-12 min of observation

Note. A minimal risk of hypoxia and arterial hypotension during the test should be ensured. If the blood pressure drops significantly during the test, the patient is connected back to the ventilator, and the arterial blood sample determines if the RAS level exceeded 55 mm Hg. And whether it increased in this case with respect to the pre-test level by> 20 mm Hg. These indicators confirm the clinical diagnosis of brain death

9. At least one of the following four criteria is met.

A. Positions 2-8 were confirmed twice in studies with an interval of at least 6 h

B. Positions 2-8 have been confirmed, and EEG also lacks electrical activity of the cerebral cortex. The second study was conducted at least 2 hours after the first, which confirmed positions 2-8

B. Confirmed positions 2-8, AND ALSO on arteriography intracranial blood flow is not determined. The second study was conducted at least 2 hours after the first, which confirmed positions 2-8

D. If the confirmation of any of the positions 2-8 is prevented by injury or condition (for example, extensive traumatic injury to the face impedes the conduct of the caloric sample), the following criteria apply. Confirmation of positions available for evaluation No signs of intracranial blood flow

The second study is carried out 6 hours after the first, which confirmed all the positions available for evaluation

SBP - mean arterial pressure; PaCO is the partial strain of CO in the arterial blood. From the Recommendations of the American Neurological Academy (1995), with changes.

Death of the brain - clinical criteria

Instrumental methods to confirm the death of the brain

There are many problems in diagnosing the clinical criteria for brain death. Often, their interpretation is not enough to diagnose this condition with 100% accuracy. In this regard, already in the first descriptions, brain death was confirmed by stopping the bioelectric activity of the brain with the help of an EEG. Various methods to confirm the diagnosis of "brain death" have been recognized throughout the world. The need for their use is recognized by most researchers and clinicians. The only objections concern the diagnosis of "brain death" only by results of paraclinical studies without taking into account the data of the clinical examination. In most countries, they are used when it is difficult to conduct clinical diagnosis and when it is necessary to shorten the observation time in patients with a clinical picture of brain death.

Death of the brain - Diagnosis

[1], [2], [3]