wabrams:
I don’t think you get it: if your brain can no longer operate the heart and lungs, you’re dead. We’re not talking about brain trauma, we’re talking about the brain ceasing to work.
I get it more than you know. Brain trauma is precisely what causes the brain to cease functioning, whether by accidental trauma or by damage incurred by cardiac or respiratory arrest. Read on…
World wide, there are two distinct mechanisms of death, those being brain stem death and irreversible cardiopulmonary arrest. These two mechanisms only differ by one thing – death is diagnosed in the presence or absence of a beating heart.
Until the advent of organ transplants, death has always been associated with cardiac standstill. Now there is a new definition for death, that of brain death. In a brain dead patient, machines replicate the brain’s function of circulating oxygenated blood. This sustained life can continue for days or weeks, sometimes much longer than doctors expect.
The higher brain stem houses the Reticular Activating System, which is responsible for maintaining our awake state. The medulla is the lower portion of the brain stem, continuous with the spinal cord, which regulates respiration and heart beat.
In severe brain trauma, when there is disruption at or below the level where the
Reticular Activating System splits to form the complex neuronal network that courses between the cerebral hemispheres, coma results. What this means is that an increase of intracranial pressure, as may occur in head injury, can squeeze the cerebellum (the part of the brain that coordinates movement) down through the foramen magnum and in the process squash the medulla against the bones of the skull. This is a common means where brain trauma results in brainstem death.
There is a physiological distinction between brainstem death and death of the whole brain. The arteries that supply the brainstem also supply the cerebellum and cerebrum (the part of the brain associated with higher functions like reasoning). When cerebral swelling and herniation occur, ischemia of the brain stem and higher structures occur, compounding mechanical damage.
Brain cells do not all die at the same time. Consequently, whatever diagnostic tests are used to determine brain death, none are capable of determining that all brain cells are dead.
These are simple medical tests that are part of a complex process that leads to the diagnosis of brainstem death. Incredibly, there exists a risk of error from inappropriate testing in patients who have reversible coma, apnea and absent cranial nerve reflexes.
It is a well researched field, but controversy still exists among medical professionals, scientists, anthropologists, and ethicists.