2.1. Terminal state
According to the classification proposed by the Russian academician V.A. Ne-govsky, the process of dying includes 3 stages.
1. Pre-agonic condition: general inhibition and motor excitement while the mental state is confused. Blood pressure cannot be determined. The pulse is palpated only on the carotid and femoral artery. Pronounced dyspnea alternating with bradypnea, cyanosis, pallor, anuria. At the end of the pre-agony the excitability of respiratory center decreases - there is a terminal pause lasting from a few seconds to 3 or 4 minutes (breathing ceases, bradycardia sets in, the pupils are dilated, corneal and pupillary light reflexes disappear).
2. Agony: the last short flash of life. After a possible very short recovery, consciousness and eye reflexes subside completely. Pulse on large arteries becomes markedly weaker; ECG shows signs of hypoxia and cardiac arrhythmia. Pathological breathing is observed, which can be of two types: convulsive with a large amplitude (2-6 respiratory movements per minute) or weak, rare, superficial, with a small amplitude. Agony ends with the last breath and heart contraction, and clinical death follows.
3. Clinical death is marked by cessation of cardiac and respiratory activity, and by a sudden depression ofbrain functions presenting in the form of a triad of clinical signs, usually easily detectable:
• asystole (no pulsation on the carotid and femoral artery);
• apnea;
• coma (unconsciousness), dilation of pupils with no light reflex.
Causes of cardiac arrest may be classified into 2 groups: cardiogenic and non-cardiogenic. The first group includes mechanical injury to the heart, embolism of coronary arteries, acute coronary syndrome (ACS) , severe cardiac arrhythmia; the second group covers cases of primary accidents in respiratory system, metabolism, and neuroendocrine system. For instance, there are records of cases of cardiac arrest at the height of a strong psycho-emotional crisis due to hyperadrenia. Such arrest of a potentially healthy heart is a most favorable option for successful resuscitation. Reversibility of pathological changes is uncertain if clinical death has followed from multiple injuries, severe brain injury, previous hypoxia, or vast blood loss with a prolonged period of pronounced hypovolemia. In these cases, the compensation capacity of the body has already been largely exhausted before resuscitation.