Researchers were able to study the moment brain death becomes irreversible in the human body for the first time, observing the phenomenon in several Do Not Resuscitate patients as they died in hospital.
Doctors are obliged to prevent death if they can, but since they can't easily monitor it, progress has been stymied.
Most of our understanding of brain death comes from animal experiments, strengthened with what we can glean from the accounts of resuscitated patients.
An international team of scientists made a breakthrough.
Within 20 to 40 seconds of oxygen deprivation, the brain enters an 'energy-saving mode' where it becomes inactive and ceases communicating with one another.
After a few minutes, the brain begins to break down as ion gradients in cells are no longer present, and a wave of energy called a spreading depolarisation is created throughout the cortex and other brain regions, causing irreversible brain damage.
A team led by a neurologist from Berlin, Germany, monitored nine patients with devastating brain injuries and found that the tsunami of brain death may actually be capable.
"After circulatory arrest, the loss of stored energy in brain cells and the start of toxic processes that eventually lead to death is marked by spreading depolarisation," Dreier explained at the time.
It is possible to reverse it up to a point when the circulation is restored.
The researchers monitored the spread of depolarisation in the patients' brains using a technology called subdural electrode strips and intraparenchymal electrode array.
The authors said that spreading depolarisation is completely irreversible if the oxidative substrate supply is re-established before the commitment point.
The findings could one day be life-saving for patients at risk of brain damage or death from cerebral infarction, but more work is needed before physicians will be able to take advantage of these discoveries.
There are no direct implications for patient care today, according to Dreier.
Knowledge of the processes involved in spreading depolarisation is essential to the development of additional treatment strategies aimed at prolonging the survival of nerve cells.
Annals of Neurology reported the findings.
The first version of this article was published in March.
