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Diagnosing brain death

Testing the eyes is one of the key methods of establishing brain death.

Testing the eyes is one of the key methods of establishing brain death.

Credits:Kate Whitley, Wellcome Images

Death is currently defined in neurological terms. Accurate diagnosis is essential. Once it is confirmed, a patient is formally declared dead. This decision hugely impacts the patient’s family, and has potential legal and financial implications elsewhere. It is also the point where a living being becomes a dead body. A life support machine may have to be turned off. In many cases, harvesting the body for organs and other tissues for donation can begin.

Brain death must be confirmed independently by two doctors to satisfy legal requirements. A number of conditions can give the appearance of brain death - comatose patients sometimes recover - so there must be a range of tests to determine the patient’s true state. Some are surprisingly crude.

Checking for pain responses and reflexes includes applying pressure to the eyes, rubbing them with cotton wool and shining bright light into the pupils. Ice-cold water might be syringed into the ear. This is painful, and even a coma victim with some brain activity would react to it. Gag and cough reflexes are checked by inserting tubing down to the lungs and applying suction.

The apnoea test is seen as the ultimate test for death of the brainstem, which controls several basic functions such as breathing. The patient is infused with 100% oxygen for several minutes. A spontaneous breath should occur if there is any remnant of active brainstem. Two flat-line EEG readings are also required in some countries before death is finally confirmed. This is not the case in the United States.



Related links

Techniques and Technologies:


S J Youngner, R M Arnold, and R Schapiro, (eds), The Definition of Death: Contemporary Controversies (Baltimore: Johns Hopkins University Press, 1999)

G Belkin, ‘Brain death and the historical understanding of bioethics’, Journal of the History of Medicine and Allied Sciences, 58/3 (July 2003), pp 325-61


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