What is it about ?
A person is brain dead when a known cause has caused irreversible damage to the brain so that all functions of the brain, including the brainstem, have stopped for good, but the heart is still beating. The diagnosis of brain death follows strict protocols, which may vary from country to country.
What are the conditions for being declared brain dead?
A patient is brain dead when:
- three doctors independently of each other judge that there is an irreversible coma of known cause (for example, a severe cerebral hemorrhage);
- all functions of the brainstem, including reflexes, are absent;
- there is no longer a reaction from the respiratory center in the brain;
- the body temperature (measured in the anus) of a hypothermic patient is at least 32 ° C.
The moment at which the third doctor finds brain death is the hour of death.
Doctors need to be sure that the damage to the brain is not due to an overdose of drugs, the presence of toxic substances in the blood, or an abnormality in the blood values. In the event of conditions which may temporarily disrupt brain function (for example, hypothermia or overdose) or in a child under one year of age, a sufficiently long follow-up period is therefore necessary to be able to carry out confirmatory tests.
How is brain death found?
Confirmatory tests
We first check whether the person is reacting to the pain. This check can be done, for example, by exerting pressure on his eye. A brain dead patient no longer reacts (no motor skills, blood pressure, or pulse). However, he may have reflex reactions from the spinal cord, but these are not his reactions.
Next, muscle tone and cranial nerve function are checked. In a brain dead patient:
- the pupils are fixed and do not react to light or other stimuli;
- the eyes do not blink and close spontaneously when the cornea is touched (corneal reflex);
- rapid rotation of the head or neck does not cause the eyes to move in the opposite direction;
- exerting pressure on the eyeball or neck does not cause the heart rate to slow down;
- there is no reaction to stimulation of the throat, trachea or large airways (for example, when moving the endotracheal intubation tube);
- the vestibulo-ocular reflex is absent, which means that injecting 50 ml of ice water into each ear canal one after the other does not trigger eye movements.
Finally, the apnea test is performed. A person in a state of brain death is in fact no longer conscious and no longer breathes spontaneously. This test therefore seeks to determine whether there is still spontaneous respiratory activity.
Additional technical examinations
When at least one physician judges that at least one element of the physical examination cannot be performed or evaluated reliably, or when there is no unanimity among the three physicians, it is advisable to carry out additional technical examinations. In some countries, imaging (for example, CT scan or MRI) is required to be able to diagnose brain death. In Belgium, this type of imaging test is requested in the presence of increased pressure in the brain (following, for example, a severe head trauma).
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