The concepts of this blog are largely taken from the book "The Undead", by Dick Teresi, which raises serious questions about the possibility that some organ donors may have a functioning cerebral cortex and therefore be aware (and possibly also feel pain) as they are cut into and their organs are harvested for transplant, and this book should be referred to for further information and references.
Disclaimer: I am not opposing organ transplantation here, but merely showing what the legal definition of death is in our present time.
What do we mean by "dead"? There is more than one answer to this question. There is what you would think is or should be the definition, what most doctors think, what many philosophers think, what various religious leaders think, what the law says, and finally, how the law is applied by doctors. Without editorializing, I will describe how the definition of "dead" has changed (I hesitate to use the word "evolved") over the history of man. Our acceptance of the definition is modified by at least three factors: (a) the normal ego cannot conceive of its own non-existence, (b) none of us wishes to be buried while still "alive", and (c) it's easier to say and think that "they" know what they are doing when a doctor declares a patient to be dead.
First, some fundamental facts. The cortex of the brain, which is what we see in our minds when we think of a brain, generates electrical and magnetic impulses while you are alive and thinking, dreaming, processing sensory input from the world, etc. These electrical signals can be detected by an ElectroEncephaloGram, or EEG, and the flow of blood and metabolic activity can be measured by a functional MRI, or fMRI as well as a PET scan.The brain stem controls breathing as well as reflexes that involve the cranial nerves, such as the corneal or blink reflex, the gag reflex, and a positive response to the apnea test---more about these tests later. Finally, the heart has its own pacemaker(s) and can beat by itself and circulate blood even when the brain stem has been totally destroyed.
I am not going to discuss the various definitions of death that operated in different societies, or before WWII, or in fact before 1968. Up until that time, it was generally felt that if your heart stopped beating (no pulse), AND you were not breathing (no signal to the diaphgram from the brainstem), you were considered to be dead. In certain cases of deep coma, some doctors insisted on a "flat line" EEG, i.e. no electrical evidence of cortical activity from the thinking part of your brain. Even then it was recognized that there were exceptions to that rule: certain drug overdoses such as glutethamide (Doriden) or cold water suffocation (drowning and a core body temperature below 95.0 degrees F) could mimic the state of death, and those patients, especially drowned children, could be revived with no apparent aftereffects.
Anesthesiologists often say that a deeply anesthetized patient is in a near-death state, in that they have to mechanically breathe for the patient. In the case of open heart surgery, the still, pulseless heart is shocked back into "life". If the anesthesiologist observes an acute increase in pulse rate or blood pressure during surgery, his/her immediate assumption is that the patient is feeling pain, and a narcotic is injected to suppress the putative pain, i.e. the anesthesia is deepened. Only if the elevated pulse and/or blood pressure does not respond to additional pain medication does he/she inject medicine to lower the pressure and the pulse. So the point here is if the pulse or blood pressure rise as an operation is being performed, the cortex of the brain may be perceiving pain.
In the August 5, 1968 of the Journal of the American Medical Association, the Harvard Committee, which contained psychiatrists, neurologists, and ethicists, but NO cardiologists issued their new guidelines for declaring death. They gave several reasons for the need for this new definition. Two of them were the need to free up ICU beds for patients who could better benefit from them, and to reduce the controversy over obtaining organs for transplantation. The conditions were (caps added by me): an unreceptive and unresponsive patient, no movements or breathing, no reflexes, and TWO FLAT EEG'S taken 24 hours apart. They reiterated the importance of this last test. Note that no mention was made of an absent pulse or a flat line EKG, but then again there were no cardiologists on the panel(!).
Then the federal government stepped in, passing the Uniform Determination of Death Act (UDDA) 1n 1981. This is now the law in all 50 states, The UDDA states that the ENTIRE brain must cease to function, irreversibly, and again it notes that drug overdose and hypothermia must be ruled out. However, unlike the Harvard statement, there is no requirement for flat-line EEG's, and certainly no requirement for a flat-line EKG. It is important to note here for the non-doctors in my reading audience that all the tests of reflexes, including calorics, doll's eyes and ciliospinal are only tests of brain stem activity or the lack thereof. There is NO reliable test for the absence of higher cortical function if an EEG is not done. No reason was given for dropping the last requirement of the Harvard Committee.
Let me close by noting that there are two well-recognized near-death neurological states in which the patients can think and sense the outside world, but doctors are unable to determine that the patient has a functioning brain. In each state, there have been cases of patients recovering and becoming fully conversant with their doctors, and describing what they felt like. One is the Locked-In Syndrome, and the other is the Persistent Vegetative State. In the locked-in syndrome the brain stem is permanently damaged or destroyed, but the cortex is fully functioning. In the persistent vegetative state, there are brain waves, a sleep-wake cycle, and spontaneous breathing. The precise definitions are unimportant except to note that such patients can recover.
P.S. Karen Ann Quinlan lived for over 10 years after she was disconnected from her respirator.