Lecture
Objective: to build students' knowledge on this topic, and to cultivate in students a sense of responsibility and moral readiness for unexpected and extreme situations.
Critical care medicine is one of the most interesting and complex branches of clinical medicine. Human life is the highest value, and we are all responsible for every life – physicians, society, the state.
Fear of misdiagnosing death drove physicians to develop methods for diagnosing death, to create special vitality tests, or to devise special burial arrangements. For example, in Munich a mortuary vault existed for more than 100 years in which the hand of the deceased was tied to a cord attached to a bell. The bell rang only once, and when the attendants came to help a patient who had awoken from a lethargic sleep, it turned out that rigor mortis had resolved. At the same time, literature and medical practice record cases of living people being delivered to the morgue after physicians mistakenly diagnosed them as dead.
Several types of death are distinguished: clinical death, biological death and final death. A subcategory includes brain death.
The onset of death is always preceded by terminal states — the pre-agonal state, agony and clinical death — which together may last for varying periods, from several minutes to hours or even days. Regardless of the rate at which death occurs, it is always preceded by the state of clinical death.
During the process of dying and clinical death, the following changes occur in the body:
1. Cessation of breathing, as a result of which blood oxygenation stops and hypoxaemia and hypercapnia develop.
2. Asystole or cardiac fibrillation.
3. Disruption of metabolism and acid-base balance, accumulation of under-oxidised products and carbon dioxide in the tissues and blood, with the development of respiratory and non-respiratory acidosis.
4. Central nervous system activity ceases. This happens through a stage of excitation, after which consciousness becomes depressed, a deep coma develops, and reflexes and the brain's bioelectric activity disappear.
5. The functions of all internal organs fade away.
Biological Death.
Biological death - the irreversible cessation of the vital functions of the body, representing the inevitable final stage of its individual existence. The work of Professor A. A. Kulyabko of Tomsk University (1866-1930) demonstrated the possibility of restoring the function of individual organs (the heart, for example) after the death of the organism as a whole.
The absolute signs of biological death include:
1. Algor mortis - the process by which the temperature of the body falls to the level of the ambient temperature.
2. The appearance of livor mortis on the skin. These are formed as a result of the post-mortem pooling of blood in the lower-lying areas, engorgement and dilation of the skin's blood vessels, and saturation of the surrounding tissue with blood.
3. Rigor mortis - the process of post-mortem stiffening of the skeletal muscles and the smooth muscle of the internal organs.
4. Decomposition - the process of breakdown of the organs and tissues of the body under the action of its own proteolytic enzymes and enzymes produced by microorganisms.
It is very difficult to determine precisely the time of transition from clinical death to biological death, yet this is very important, since it is linked to the need for resuscitation measures or the lack of it.
Terminal states – acute critical disorders of the body's vital functions, involving catastrophic depression of cardiac activity, respiration, gas exchange and metabolism.
Classification of terminal states:
Three types of terminal states are distinguished: the pre-agonal state, agony, and clinical death.
• Pre-agonal state: The patient is lethargic, marked dyspnoea is noted, the skin is pale and cyanotic, blood pressure is low (60-70 mmHg) or cannot be measured at all, and the pulse is weak and rapid.
• Agony: A deep stage of the dying process in which consciousness is absent, the pulse is thready or disappears altogether, and blood pressure cannot be measured. Breathing is shallow, rapid, convulsive, or considerably slowed.
• Clinical death occurs immediately after breathing and circulation stop. It is a distinctive transitional state between life and death, lasting 3-5 minutes. The main metabolic processes are sharply reduced and, in the absence of oxygen, proceed by means of anaerobic glycolysis. After 5-6 minutes irreversible changes develop, above all in the central nervous system, and true, or biological, death occurs.
Pre-agony, agony and clinical death belong to the terminal (final) states. A characteristic feature of terminal states is the dying organism's inability to emerge from them on its own without outside help, even if the causative factor that produced them is no longer acting (for example, with a loss of 30% of blood volume and cessation of bleeding the body survives on its own, whereas with a loss of 50% it dies even if the bleeding has been stopped).
Thus, clinical death, with its reduced metabolic process in the cells of the cerebral cortex, is a reversible process of dying.
Cardiac arrest can be sudden or gradual - occurring against the background of a prolonged chronic illness, in which case it is preceded by the pre-agonal state and agony. The causes of sudden cardiac arrest include myocardial infarction, blockage (obstruction) of the upper airway by foreign bodies, reflex arrest
of the heart, cardiac injury, anaphylactic shock, electrical injury, drowning, severe metabolic disturbances (hyperkalaemia, metabolic acidosis).
An important factor affecting the process of dying is the ambient temperature. As the temperature falls, metabolism proceeds less intensively, i.e. with a lower tissue requirement for oxygen. Hypothermia therefore increases the resistance of the cerebral cortex cells to hypoxia, prolonging the period of clinical death; however, a person or animal can only be cooled under anaesthesia and deep neurovegetative blockade, otherwise the body will respond to the cold exposure by increasing heat production, and cooling of the body will not occur until all energy sources have been used up.
Social death (decerebration, decortication).
This period begins with the death of the cerebral cortex cells and continues for as long as it remains possible to restore breathing and circulation, which, however, does not lead to the restoration of cerebral cortex function
Signs of cardiac arrest, i.e. of the onset of clinical death:
1) absence of a pulse on the carotid artery;
2) dilation of the pupils with absence of their reaction to light;
3) cessation of breathing;
4) absence of consciousness;
5) pallor, less often cyanosis, of the skin;
6) absence of a pulse on the peripheral arteries;
7) absence of blood pressure;
8) absence of heart sounds.
The time taken to establish a diagnosis of clinical death should be kept to an absolute minimum.
Absolute signs: absence of a pulse on the carotid artery, cessation of breathing, dilation of the pupils with absence of their reaction to light. If these signs are present, resuscitation should be started immediately.
Cardiopulmonary resuscitation
There are four stages of cardiopulmonary resuscitation:
I - restoration of airway patency;
II - artificial lung ventilation;
III - cardiac massage;
IV - differential diagnosis, drug therapy, cardiac defibrillation.
One of the earliest and most valuable signs of the onset of death is the «cat's eye phenomenon», sometimes called Beloglazov's sign. The shape of a person's pupil is determined by two parameters, namely: the tone of the muscle that constricts the pupil, and intraocular pressure. The main factor here is muscle tone. When nervous system function is absent, innervation of the pupil-constricting muscle ceases and its tone disappears. When the eyeball is compressed between the fingers in a lateral or vertical direction - which must be done carefully so as not to damage the eyeball - the pupil takes on an oval shape. A contributing factor in the change of pupil shape is the fall in intraocular pressure, which determines the tone of the eyeball, and which in turn depends on arterial blood pressure. Thus, Beloglazov's sign, or the «cat's eye phenomenon», indicates the absence of muscle innervation and, simultaneously, a fall in intraocular pressure linked to arterial pressure.
The Instruction on determining the criteria and procedure for establishing the moment of a person's death and for discontinuing resuscitation measures, approved by the Ministry of Health., provides for the certification of a person's death either as biological death on the basis of the presence of post-mortem changes, or as brain death, which is established in the prescribed manner. Resuscitation measures may be discontinued only upon certification of a person's death on the grounds of brain death, or if they prove ineffective within 30 minutes. Resuscitation measures are not carried out where there are signs of biological death, nor where a state of clinical death occurs against the background of the progression of reliably established incurable diseases or the incurable consequences of acute trauma incompatible with life.
Knowledge check:
1.Describe clinical and biological death.
2.What tests for determining signs of life do you know?
3.Give a definition of the terminal state.
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