August 03, 2006

What is death?

Dr. R.L. Bijlani Editor's note: Written by an eminent physiologist, this article explores different aspects of death.
Death is both an event and a process. It is an event after which a collection of matter that was once alive becomes just a collection of matter. Nobody has seen what it is that escapes from the living body during this radical transformation. That is why the phenomenon called life is shrouded in mystery. It naturally follows that the event during which it escapes is equally mysterious. But the event called death is the culmination of a process from which it cannot be divorced, viz. the process of aging.
In a broad sense, aging is a continuous process which begins with conception and ends with death. But what is more relevant to death is the impairment of function seen in the latter part of life. In this restricted sense, aging is due to a decrease in the efficiency of homeostatic mechanisms. Hence the body is unable to mount an adequate response to challenges originating in the external or internal environment. This increases the vulnerability of the individual to a number of diseases, to one of which he finally succumbs during the event called death. Although progress towards the event of death may be a slow and insidious process, the event is precipitated when the functional capacity of at least one of the vital organs falls below a critical minimum. When that happens, the heart stops beating or the lungs stop breathing. In either case, the result is that no part of the body any longer has a continuous supply of oxygen. However, modern technology may create situations which are not so clear-cut. The lungs may be made to work like bellows by mechanical means in a person who is unlikely to be ever able to regain meaningful life. That is what has necessitated the concept of brain death. If all the features of brain death are present, it is no longer justified to continue artificial life-support. But since artificial life-support may maintain a large number of organs in a viable state long after brain death, these organs are still fit to be transplanted where they can continue to live in another body.
I. Physical aspects of death
Clinical death
Doctors know very little about death. The only course in which they learn the subject at some length is forensic medicine. This is so because it is commonly assumed that their job is to postpone death as much as possible. If inspite of their efforts a patient dies, it signifies their failure, and they are out of the picture except perhaps to answer, in some cases, unpleasant medicolegal questions such as the time of death or the cause of death. That is why, confronted with an incurable fatal disease, doctors are often unwilling to face the issue. They avoid talking about impending death to the patient or relatives. They are ill-equipped to talk to them in a manner that would make acceptance of the inevitable easier. Instead, they hide their distaste for death behind a cloak of intense activity. In the pre-ICU days, the parting service to the patient was cardiopulmonary resuscitation and intra-cardiac adrenaline. These days, the patient is transferred to the intensive care unit (ICU) where tubes, flashes and beeps occupy the attention of doctors and nurses more than the patient to whom the equipment is connected. It is only recently that the importance of facing the issue of dying has been recognized, and some attention given to the best way of doing so (1). But this new trend is yet to get reflected in the medical curricula.
Pronouncing clinical death
Till about forty years ago, the boundary between life and death was clinically well defined. Death was defined as total stoppage of blood circulation and a consequent cessation of the animal and vital functions, such as respiration and pulsation (2). Doctors pronounced death when respiration and heartbeat had ceased, and when it seemed certain that these functions would not start and could not be started again (3). This could be presumed if heartbeat and breathing remained absent for at least ten minutes because the brain survives without oxygen for only about three minutes, and without a living brain, resumption of circulation and respiration is impossible. But now that respiration and circulation can be maintained artificially for long periods of time, brain death has become an important criterion of death. Now death is defined as the permanent and irreversible cessation of function of any one of the three interconnected vital systems, viz. nervous system, circulatory system and respiratory system (4). If any one of these systems fails, the other two also fail because the three systems are interlinked. The criteria of brain death are:
a. fixed, dilated pupils, unresponsive to light.b. absence of corneal reflex, vestibuleocular reflex and cough reflex.c. absence of cranial motor nerve responses to painful stimuli.d. inability to breathe when the mechanical assistance provided by the ventilator is temporarily withdrawn.e. coma and inability to breathe spontaneously continuously for at least six hours.f. EEG silence continuously for at least thirty minutes. EEG silence is defined as an absence of electrical potentials over 2 microvolts from symmetrically placed electrode pairs over 10cms apart and with an interelectrode resistance of between 100 and 10,000 ohms (5).
However, very few countries insist that an EEG be available for determining brain death: clinical criteria are considered adequate. Being an expensive facility, EEG cannot be done in every hospital. Brain death has to be certified by a team of doctors consisting of a neurologist, anaesthesiologist and an experienced doctor of the intensive care unit of the hospital. The patient should be examined by the team at least twice at an interval of 6-12 hours. Furthermore, none of the members of the team should have any interest in transplantation of an organ from the patient.
The criteria of brain death have become necessary because artificial life-support systems can today keep intact in several patients the two cardinal signs of life, heartbeat and breathing, for several months after all reasonable hope of resuscitation has disappeared. Technology can thus maintain a semblance of life when the person is not alive any more. Therefore additional criteria are needed to determine the point at which hope may be abandoned, and support systems switched off. On the other hand, strict guidelines for certifying brain death are also necessary because artificial life-support can keep several organs in the body fit for transplantation for several hours after the person as a whole is, for all practical purposes, dead.

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