In medical science, death is declared after certain conditions are met. Normally it’s the cessation of a heart beat , a lack of arterial blood pressure (ABP) and no respiration. Without adequate blood flow and oxygenation, brain death will occur, almost immediately. Or does it? The brain controls the heart and lungs, as it does the rest of the body. If brain death occurs, surely the heart and lungs will stop and blood pressure will be non-existent, but what if the opposite happens? If the heart ceases to beat, and the lungs do not inflate, can the brain continue? In a recent research study from a Canadian hospital, it appears that yes, in some very limited cases, it can.
Doctors from the University of Western Ontario report that in one patient in a Canadian intensive care unit, persistent brain activity was found even after clinical death had been officially declared. This phenomenon occurred in one patient of four studied, all of whom had been on extended life support. In each of the four patients the decision was made to discontinue life support, which almost certainly guarantees a speedy death. However in one, some brain activity continued.
In all four patients, doctors had ascertained death from a variety of measures including heart rate, ABP, respiration and unreactive pupils. However, for upwards of 10 minutes post declaration, one patient showed a specific kind of brain wave activity. Delta waves, which are normally present when a person is in a state of deep sleep, continued in this patient for more than ten minutes, something not seen before. In studies of lab rats, there is a specific brain wave burst, called the “death wave” that is seen in rats after decapitation but was not seen in these four patients. In the one patient referenced in the study, the brain activity seen was distinctly not a death wave, but rather a common kind of brain wave that is seen when patients who are fully alive are in a state of deep sleep.
In their study, published in The Canadian Journal of Neurological Sciences, the researchers write, "In one patient, single delta wave bursts persisted following the cessation of both the cardiac rhythm and arterial blood pressure (ABP)." The team was careful to say that this finding, in only one single patient, cannot be extrapolated into anything more than the need for more study. In lab rats, who have similar biology and brain activity to humans, cardiac death occurs about a minute before the death wave that signals the end of brain inactivity. It is this moment of brain death that truly marks the cessation of life, but in the case of this one human patient, that line was blurred.
On possible explanation is that the brain wave readings were a result of machine or human error. In their published work the study authors wrote, “It is difficult to posit a physiological basis for this EEG activity given that it occurs after a prolonged loss of circulation," the researchers write. These waveform bursts could, therefore, be artefactual [human error] in nature, although an artefactual source could not be identified." The best conclusion the Canadian team could offer was that the way death is declared and how each patient’s particular biology reacts in death is an area that deserves much more study. The video below talks more about this singular patient and the brain wave activity observed. Take a look to learn more.
Sources: Discover Magazine, The Canadian Journal of Neurological Sciences, BigThink.com