Clinical death is a reversible stage of dying that occurs at the moment of cessation of cardiac and respiratory activity. It is characterized by the absence of consciousness, pulse on the central arteries and chest excursions, dilation of the pupils. It is diagnosed according to the data obtained during the examination, palpation of the carotid artery, listening to heart tones and pulmonary noises. An objective sign of cardiac arrest is small-wave atrial fibrillation or isoline on an ECG. Specific treatment – measures of primary cardiopulmonary resuscitation, transfer of the patient to a ventilator, hospitalization in the ICU.
Clinical death (CD) is the initial stage of the death of the body, lasting for 5-6 minutes. During this period, metabolic processes in tissues slow down sharply, but they do not stop completely due to anaerobic glycolysis. Then irreversible changes occur in the cerebral cortex and internal organs, making it impossible to revive the victim. The duration of the condition depends on a number of factors. At a low ambient temperature it increases, at a high temperature it decreases. It also matters how the patient died. Sudden death on the background of relative stability lengthens the reversible period, slow exhaustion of the body in incurable diseases – reduces.
Among the factors causing CD, all diseases and injuries that lead to the death of the patient can be attributed. This list does not include accidents in which the victim’s body receives significant damage incompatible with life (head crushing, burning in a fire, decapitation, etc.). It is generally accepted to divide the causes into two large groups – related and unrelated to direct damage to the heart muscle:
- Cardiac. Primary disorders of myocardial contractility caused by acute coronary pathology or exposure to cardiotoxic substances. They provoke mechanical damage to the cardiac muscle layers, tamponade, disturbances in the work of the conducting system and the sinus-atrial node. Circulatory arrest may occur against the background of acute myocardial infarction, electrolyte imbalance, arrhythmias, endocarditis, rupture of an aortic aneurysm, ischemic disease.
- Non-cardiac. This group includes conditions accompanied by the development of severe hypoxia: drowning, suffocation, airway obstruction and acute respiratory failure, shocks of any origin, embolisms, reflex reactions, electric shock, poisoning with cardiotoxic poisons and endotoxins. Fibrillation with subsequent cardiac arrest may occur with improper administration of cardiac glycosides, potassium preparations, antiarrhythmics, barbiturates. A high risk is noted in patients with poisoning with organophosphate compounds.
After stopping breathing and blood circulation, destructive processes begin to develop rapidly in the body. All tissues experience oxygen starvation, which leads to their destruction. The most sensitive to hypoxia are the cells of the cerebral cortex, which die a few tens of seconds after the cessation of blood flow. In the case of decortication and brain death, even successful resuscitation measures do not lead to full recovery. The body continues to live, but there is no brain activity.
When the blood flow stops, the blood coagulation system is activated, microthrombs form in the vessels. Toxic tissue breakdown products are released into the blood, metabolic acidosis develops. The pH of the internal environment is reduced to 7 and below. Prolonged absence of blood circulation causes irreversible changes and biological death. Successful resuscitation ends with the restoration of cardiac activity, metabolic storm, the emergence of post-resuscitation disease. The latter is formed due to ischemia, thrombosis of the capillary network of internal organs, significant homeostatic shifts.
It is characterized by three main signs: the absence of effective heart contractions, breathing and consciousness. The undoubted symptom is all three signs present in the patient at the same time. CD on the background of retained consciousness or palpitation is not diagnosed. Independent residual respiration (gasping) can persist for 30 seconds after the blood flow stops. In the first minutes, individual ineffective myocardial contractions are possible, which lead to the appearance of weak pulse tremors. Their frequency usually does not exceed 2-5 times per minute.
Secondary signs include the absence of muscle tone, reflexes, movements, and the unnatural position of the victim’s body. The skin is pale, earthy. Blood pressure is not determined. After 90 seconds, the pupils dilate to a diameter of more than 5 mm without reacting to light. The facial features are pointed (Hippocratic mask). Such a clinical picture has no special diagnostic significance in the presence of the main signs, therefore, the examination is carried out during resuscitation measures, and not before they begin.
The main complication is the transition from clinical death to biological death. This finally happens after 10-12 minutes from the moment of cardiac arrest. If blood circulation and respiration were restored, but clinical death lasted more than 5-7 minutes before the start of treatment, brain death or partial impairment of its functions is possible. The latter manifests itself in the form of neurological disorders, posthypoxic encephalopathy. In the early period, the patient develops post-resuscitation disease, which can lead to multiple organ failure, endotoxicosis and secondary asystole. The risk of complications increases in proportion to the time spent in conditions of circulatory arrest.
Clinical death is easily determined by external symptoms. If the pathology develops in a medical institution, additional hardware and laboratory methods are used. This is necessary to determine the effectiveness of resuscitation measures, to assess the severity of hypoxia and acid-base balance disorders. All diagnostic manipulations are carried out in parallel with the work on restoring the heart rhythm. To confirm the diagnosis and monitor the effectiveness of the measures taken, the following types of studies are used:
- Physical. Are the main method. Upon examination, characteristic signs of CD are detected. During auscultation, coronary tones are not heard, there are no respiratory noises in the lungs. The presence of a pulse outside the ICU is determined by pressing on the projection area of the carotid artery. Probing of shocks on peripheral vessels has no diagnostic value, since in agonal and shock conditions they can disappear long before the cessation of cardiac activity. The presence or absence of breathing is assessed visually by the movements of the chest. It is impractical to conduct a test using a mirror or a suspended thread, since this requires additional time. HELL is not defined. Tonometry outside the ICU is performed only if there are two or more resuscitators.
- Instrumental. The main method of instrumental diagnostics is electrocardiography. It should be borne in mind that the isolation corresponding to a complete cardiac arrest is not always registered. In many cases, individual fibers continue to contract randomly, without providing blood flow. On an ECG, such phenomena are expressed in fine waviness (amplitude less than 0.25 mV). There are no clear ventricular complexes on the film.
- Laboratory. They are prescribed only for successful resuscitation measures . The main studies are considered to be ABB, electrolyte balance, and biochemical parameters. Metabolic acidosis, an increased content of sodium, potassium, proteins and tissue breakdown products are detected in the blood. The concentration of platelets and coagulation factors is reduced, hypocoagulation phenomena are present.
Restoration of vital functions of the patient is carried out with the help of basic and specialized resuscitation measures. They should be started as early as possible, ideally no later than 15 seconds after the circulatory arrest. This allows you to prevent decortication and neurological pathology, reduce the severity of post-resuscitation disease. Measures that did not lead to the restoration of the rhythm for 40 minutes from the last electrical activity are considered unsuccessful. Resuscitation is not indicated for patients who have died as a result of a documented, long-term incurable disease (oncology). The list of measures aimed at resuming heart contractions and breathing includes:
- The basic complex. It is usually implemented outside the medical facility. The victim is laid on a hard, flat surface, his head is thrown back, a roller made of improvised material (bag, jacket) is placed under his shoulders. The lower jaw is pushed forward, the airways are cleaned of mucus and vomit with fingers wrapped in cloth, the existing foreign bodies and false teeth are removed. Indirect heart massage is performed in combination with mouth-to-mouth artificial respiration. The ratio of compressions and breaths should be 15:2, respectively, regardless of the number of resuscitators. The massage speed is 100-120 thrusts / minute. After the pulse is restored, the patient is laid on his side, his condition is monitored until the arrival of doctors. Clinical death may occur again.
- Specialized complex. It is carried out in the conditions of the ICU or ambulance. To ensure the excursion of the patient’s lungs, the patient is intubated and connected to a ventilator. An alternative option is to use an Ambu bag. A laryngial or facial mask can be used for non-invasive ventilation. If the cause was persistent obstruction of the respiratory tract, a conicotomy or tracheostomy with the installation of a hollow tube is indicated. Indirect massage is performed manually or with a cardiopump. The latter facilitates the work of specialists and makes the event more effective. In the presence of fibrillation, the rhythm is restored using a defibrillator (electric pulse therapy). Discharges with a power of 150, 200, 360 J are used on bipolar devices.
- Medication allowance. During resuscitation, the patient is given intravenous administration of adrenaline, mezaton, atropine, calcium chloride. To maintain blood pressure after the rhythm is restored, pressor amines are supplied through a syringe pump. To correct metabolic acidosis, sodium bicarbonate is used in the form of an infusion. The increase in BCC is achieved due to colloidal solutions – rheopoliglyukin, etc. Correction of the electrolyte balance is realized taking into account the information obtained during the laboratory study. Salt solutions may be prescribed: acesol, trisol, disol, saline sodium chloride solution. Immediately after the restoration of the heart, antiarrhythmic drugs, antioxidants, antihypoxants, and means that improve microcirculation are indicated.
Measures are considered effective, during which the patient’s sinus rhythm was restored, systolic blood pressure was set at 70 mm Hg or higher, heart rate is kept within 60-110 beats. The clinical picture indicates the resumption of blood supply to tissues. There is a narrowing of the pupils, the restoration of their reaction to the light stimulus. Skin color returns to normal. The appearance of independent breathing or the immediate return of consciousness immediately after resuscitation is rare.
Prognosis and prevention
Clinical death has an unfavorable prognosis. Even with a short period of absent blood circulation, the risk of damage to the central nervous system is high. The severity of the consequences increases in proportion to the time that has elapsed since the development of pathology before the start of the work of resuscitators. If this period was more than 5 minutes, the possibility of decortication and posthypoxic encephalopathy increases many times. With an asystole of more than 10-15 minutes, the chances of resuming the work of the myocardium sharply decrease. The cerebral cortex is guaranteed to be damaged.
Specific preventive measures include hospitalization and constant monitoring of patients with a high risk of cardiac death. At the same time, therapy is carried out aimed at restoring the normal functioning of the cardiovascular system. Specialists working in medical institutions should carefully observe the dosages and rules for the administration of cardiotoxic drugs. A non-specific preventive measure is compliance with safety regulations in all spheres of life, which reduces the risk of drowning, injury, asphyxia resulting from an accident.