A better understanding of brain death

There are two ways to die: either the heart stops beating for good, leading to a halt in cerebral vascularization and consequent anoxia (oxygen deprivation) of the brain, leading to death; or the brain stops functioning, leading to cardiorespiratory arrest (loss of vital cerebral functions), leading to death. In the event of irreversible loss of encephalic functions (particularly the brain stem, responsible for regulating breathing and heart rate), breathing ceases and the heart stops beating within minutes.

In this case, thanks to advanced resuscitation techniques, it is possible to maintain, for a limited period of time, a circulatory function that allows oxygenation of the organs (by mechanical ventilation and cardiac stimulation) after death has been declared: this is the state of encephalic death (EME), or "brain death", the declaration of which makes it possible to envisage, under certain conditions, the possibility of organ and/or tissue removal.

It's a death that's difficult for loved ones to understand, because the body of the deceased in a state of brain death is still warm and colorful. It is therefore neither a death as we usually think of it, with a pale, cold, immobile body, nor a person "in a coma", likely to regain consciousness. The vital functions have been irreversibly destroyed, the person is dead, and cardiorespiratory activity can only be maintained for a few hours, thanks to the assistance of machines and the administration of intravenous medication.

The diagnosis of brain death follows a very precise protocol.

It is first established by a clinical examination, which consists in noting the total absence of consciousness and sensory and motor activity, the abolition of brain stem reflexes, and in particular respiratory function (absence of spontaneous ventilation).

It is then followed by a paraclinical examination: 2 electroencephalograms (EEG) 4 hours apart (to check that there is no electrical activity in the brain, known as a "flat" EEG), or the injection of a contrast medium to check, by means of cerebral imaging (angiography, angioscanner...), that there is no complete interruption of cerebral vascularization.

Once these tests have been carried out, a diagnosis of encephalic death can be made, leading to the drafting of a "Procès-Verbal de constat de mort" (death certificate) by two separate doctors, followed by the signing of a death certificate by one of the two doctors. The time of death indicated on the certificate is the time of the 2nd electroencephalogram (or CT scan), attesting to the state of encephalic death. It should be noted that these paraclinical examinations can be interpreted remotely, via telemedicine.

Encephalic death is relatively rare: around 1% of hospital deaths, or 5,000 cases per year in France. However, this handful of deaths represents up to 80% of organ harvesting possibilities. Artificially maintaining cardiac activity after death makes it possible to perfuse and oxygenate organs, and keep them in good condition for transplantation.

The procedure for organ and/or tissue removal is governed by articles L 1332 of the French Public Health Code. The declaration of death is a prerequisite for triggering this procedure. Once death has been declared, the medical teams at the hospital's organ procurement and critical care coordinating centers carry out a series of medical and legal checks (looking for any opposition the deceased may have expressed during his or her lifetime, approaching relatives who are also called upon to testify to any opposition to organ donation that the deceased may have expressed during his or her lifetime), as well as clinical checks (looking for medical history, quality of potential grafts, etc.). The Agence de la biomédecine, which guarantees the anonymity, fairness and gratuity of donation, then carries out compatibility searches with potential recipients, allocates grafts and puts transplant teams in touch with each other.

The stakes are high: for every brain-dead person who can be harvested for transplantation, up to seven lives can be saved. For medical teams in the field, every potential donor counts, and a good understanding of the state of brain death by the deceased's next of kin is therefore decisive in carrying out their mission.