Vardanyan Sh.A.
Avagyan K.K.
Forensic medicine
DEATH AND ITS CAUSES
2006
DEATH AND ITS CAUSE
Thanatology deals with death in all its aspects. Death is of two types : (1) somatic, systemic or clinical, and (2) molecular or cellular.
Somatic > Death: It is the complete an3 irreversible stoppage of the circulation, respiration and brain functions, but there is no legal definition of death. The question of death is important in resuscitation and organ transplantation. As long as circulation of oxygenated blood is maintained to the brain stem, life exists. Whether the person is alive or dead can only be tested by withdrawal of artificial maintenance. A person who cannot survive upon withdrawal of artificial maintenance is dead. The success of a homograft mainly depends upon the type of tissue involved, and the rapidity of its removal after circulation has stopped in the donor. Cornea can be removed from the dead body within six hours, skin in 24 hours, bone in 48 hours and blood vessels within 72 hours for transplantation. Kidneys, heart, lungs and liver must be obtained soon after circulation has stopped as they deteriorate rapidly.
THE MOMENT OF DEATH : Historically (medically and legally), the concept of death was that of "heart and respiration death", i.e. stoppage of spontaneous heart and breathing functions. Heart-lung bypass machines, mechanical respirators, and other devices, however have changed this medically in favor of a new concept "brain death", that is, irreversible loss of Cerebral function.
Brain death is of three types : (1) Cortical or cerebral death with an intact brain stem. This produces a vegetative state in which respiration continues, but there is total loss of power of perception by the senses. This state of deep coma can be produced by cerebral hypoxia, toxic conditions or widespread brain injury. (2) Brain stem death, where the cerebrum may be intact, though cut off functionally by the stem lesion. The loss of the vital centers that control respiration, and of the ascending reticular activating system that sustains consciousness, cause the victim to be irreversibly comatose and incapable of spontaneous breathing. This can be produced by raised intracranial pressure, cerebral oedema, intracranial hemorrhage, etc.(3) Whole brain death (com¬bination of 1 and 2).
Brain Death: A current fairly conservative medical definition of death, that is "brain death" permitting removal of vital organs, such as heart or liver is irreversible coma, consisting of : (1) Deep unconsciousness with no response to external stimuli or internal need; (2) No movements, no spontaneous breathing ; (3) Cessation of spontaneous cardiac rhythm without assistance; (4) No reflexes (except occasionally spinal reflexes), (5) Bilateral dilatation and fixation of pupils; (6) Flat isoelectric EEG (confirmatory but not essential); provided that (a] all of the previously mentioned are present for a 24 hour period; (b) patient's body temperature should not be below 32°C. and (d) metabolic and endocrine disturbances, which can be responsible for coma should have been excluded. There should be no profound abnormality of the serum electrolytes. acid-base balance or blood glucose.
BRAIN STEM: The tissue in the floor of the aqueduct, between the third and fourth ventricles of the brain contains ascending reticular activating system. The ascending reticular activating substance, which extends throughout the brainstem from the spinal cord to the subthalamus, determines arousal!. Damage to the ascending reticular activating substance or damage to areas of the cerebral hemispheres results in disturbance of normal consciousness. If this area is dead, the person is irreversibly unconscious and apnoeic (incapablle of breathing).
Functions of brainstem: A properly functioning paramedian tegmental area of the brain stem is a precondition for full consciousness which enables the cerebral hemispheres to work in an integrated way. Lesions of this part are associated with profound coma. The brainstem is also responsible for the respiratory drive, and in large measure (but not exclusively) for the maintenance of blood pressure. All motor output from the brain travel through the brainstem. Apart from vision and smell, all the sensory traffic coming into the brain arrives through the brainstem. The brainstem also mediates the cranial nerve reflexes.
Diagnosis of brainstem death: (1) The cause of coma should be established. The cause must be irremediable, structural brain damage. (2) It should be made sure that the patient is not suffering from drug intoxication, hypothermia, or profound metabolic disturbance. (3) Brainstem reflexes should be absent, (a) Pupillary response to light. (b).Corneal reflex, (c) Vestibulo-ocular reflex. (d) No grimacing in response to painful stimuli applied either to trigeminal territory or. to the limbs. (4) The patient should be deeply comatose, and the effects of depressant drugs, primary hypothermia or potentially reversiblle metabolic and endocrine distrubances as the cause of continuation of coma must be excluded.
The diagnostic tests should be determined by two doctors . The test should be repeated at least once, the interval depending on the opinion of the doctors. If it is proposed to request organ donation, the doctor who treated the patient or diagnosed brainstem death should not be part of the transplant team.
Whole or part of the brain can be irreversibly damaged due to hypoxia, cardiac arrest, intracranial haemorrhage, poisoning and trauma to the brain. If the cortex alone is damaged, the patient passes into deep coma, but the brainstem will function to maintain spontaneous respiration. This is called "persistent vegetative state" and death may occur months or years later due to extension of cerebral damage or from intercurrent infection.
If the brainstem is damaged due to trauma, cerebral oedema, haemorrhage, hypoxia or infection, such as poliomyelitis, respiratory motor system fails, and damage to the ascending reticular activating system causes permanent loss of consciousness, and higher centres in the cortex are also irreversibly damaged causing 'whole brain death'.
Tissue and organ transplantation; (1) Homologous donation means grafting of the tissue from one part of the body to another in the same patient, such as skin or bone. (2) Live donation includes blood and bone marrow transfusion. Live organ donation include kidney and parts of the liver. (3) Cadaveric donation: Most organs must be obtained while the donor heart is still beating to improve chances of success.
Stupor: the patient appears to be asleep and shows little or no spontaneous activity, responding only to vigorous stimulation and then lapsing back into somnolence.
Vegetative State: In this the patient breathes spontaneously, has a stable circulation and shows cycles of eye opening and closing which may simulate sleep and waking, but is unaware of the self and the environment. It is usually seen in patients with diffuse, bilateral cerebral hemisphere disturbance with an intact brainstem, though it can occur with damage to the most rostal part of the brainstem.
THE BEATING-HEART DONOR: After brain stem death has been established, the retention of the patient on the ventilator, facilitates a fully oxygenated cadaver trans¬plant, the so-called "beating-heart donor". The results of the transplant are much improved. This has no legal sanction.
Molecular Death: It means the death of cells and tissues individually, which takes place usually one to two hours after the stoppage of the vital functions. Molecular death occurs piecemeal. Individual cells will live on their residual oxygen for a variable time after the circulation has stopped, depending on the metabolic activity of the cell. The subsequent changes occur due to metabolic dysfunction and later from structural disintegration. Nervous tissues die rapidly, the vital centres of the brain in about five minutes, but the muscles live up to one to two hours.
MODES OF DEATH: According to Bichat, there are three modes of death, depending on whether death begins in one or other of the three systems, irrespective of what the remote causes of death may be. These modes are: (I) Coma. (2) Syncope, and (3) Asphyxia.
Anoxia: According to Gordon (1944) the stoppage of vital functions depend upon tissue anoxia. Anoxia means "lack of oxygen". It may be: (1) Anoxic anoxia: In this type, oxygen cannot reach the blood, because of lack of oxygen in the lungs. This occurs: (a) from breathing in a contaminated atmosphere, e.g., from exposure to the fumes in wells and tanks, or from exposure to sewer gas, (b) from mechanical interference with the passage of air into or down the respiratory tract, e.g., in smothe-ring, drowning, choking, hanging, strangulation, traumatic asphyxia and certain forms of acute poisoning. (2) Anaemic anoxia: In this type, oxygen-carrying capacity of the blood is reduced, e.g., acute massive haemorrhage, poisoning by carbon monoxide, chlorates, nit ates, coaltar derivatives. (3) Stagnant anoxia: In this type, impaired circulation results in a reduction of oxygen delivery to the tissues, e.g., heart failure, embolism and shock. (4) Histotoxic anoxia: In this type, the enzymatic processes by which the oxygen in the blood is used by the tissues are blocked, e.g., acute cyanide poisoning. Anoxic anoxia due to lack of oxygen in the inspired air or ^mechanical obstruction to respiration, is usually known as asphyxia or mechanical asphyxia. These four types of anoxia ultimately lead to cardiac failure and death.
Asphyxia
Asphyxia is a condition caused by interfe¬rence with respiration, or due to lack of oxygen in respired air due to which the organs and tissues are deprived of oxygen (together with failure to eliminate CO2), causing unconsciousness or death. Nervous tissues are affected first by deficiency of oxygen and their functions are disturbed even by mild oxygen lack. The term asphyxia indicates a mode of dying, rather than a cause of death. The neurons of the cerebral cortex will die in 3 to 7 minutes of complete oxygen deprivation, and the other nerve cells remain alive for a little longer time. Irreversible cortical damage may occur if oxygenated blood fails to perfuse the brain up to 7 to 10 minutes. Subnormal oxygen in the blood supply to the brain causes rapid unconsciousness. In all forms of asphyxia, heart may continue to beat for several minutes after stoppage of respiration. The rule of thumb is: breathing stops within twenty seconds of cardiac arrest, and heart stops within twenty minutes of stopping of breathing.
Types and Causes: (1) Mechanical: In this the air-passages are blocked mechanically, (a) Closure of the external respiratory orifices, as by closing the noseband mouth with the hand or a cloth or by filling these openings with mud or other substance, as in smothering, (b) Closure of the air-passages by external pressure on the neck, as in hanging, strangulation, throttling, etc. (c) Closure of the air-passages by the impaction of foreign bodies in the larynx or pharynx as in choking, (d) Prevention of entry of air due to the air-passages being filled with fluid, as in drowning, (e) External compression of the chest and abdominal walls interfering with respiratory movements, as in traumatic asphyxia.
(2) Pathological: In this, the entry of oxygen
to the lungs is prevented by disease of the upper
respiratory tract or of the lungs, e.g., bronchitis.
acute oedema of the glottis, laryngeal spasm, tumours
and abscess. Paralysis of the respiratory muscles
may result from acute poliomyelitis.
(3) Toxic: Poisonous substances prevent the
use of oxygen, (a) The capacity of haemoglobin to
bind oxygen is reduced, e.g., poisoning by CO. (b)
The enzymatic processes, by which the oxygen in
the blood is utilised by the tissues are blocked, e.g.,
cyanides, (c) Respiratory centre may be paralysed
In poisoning by opium, barbiturates, strychnine, etc.
(d) The muscles of respiration may be paralysed
by poisoning by gelsemium.
(4) Environmental: (a) Insufficiency of
oxygen in the inspired air, e.g., enclosed places,
trapping in a disused refrigerator or trunk, (b)
Exposure to irrespirable gases in the atmosphere,
e.g. sewer gas, CO, CO2. (c) Exposure to high
altidue.
(5) Traumatic: (a) Pulmonary embolism
from femoral vein thombosis due to an injury to the
lower limb, (b) Pulmonary fat embolism from
fracture of long bones, (c) Pulmonary air embolism
from an incised wound of internal jugular vein, (d)
Bilateral pneumothorax from injuries to the chest
wall or lungs.
(6) Postural asphyxia: This is seen where
an unconscious or stuporous person, either from
alcohol, drugs or disease, lies with the upper half
of the body lower than the remainder. The inverted
position allows the abdominal viseera to push up
the diaphragm and this together with reduced
respiratory effect can cause death. It may also
resullt from forcible flexion of the neck on the chest.
Positional asphyxia is always accidental and
associated with alcohol or drug intoxication. An