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January 18, 2012
The coma is heavy, sharply developing morbid condition which is characterized by the progressing oppression of activity of the central nervous system with loss of consciousness, the accruing circulatory disturbance, breath and other vital functions, disturbance of reaction to irritants from the outside.
The concept "coma" of narrow sense means considerable extent of oppression of work of TsNS which heavier only the death of a brain is already. In this case the dead faint, an areflexia – lack of all or one reflex, disorder of regulation of functions of life support is characteristic of a coma.
The coma is not an independent deviation from a normality or a disease, it arises as complication in a number of diseases which are followed by considerable changes in functioning of a nervous system or because of primary damage of any structures of a brain that can arise, for example, at a severe craniocereberal injury. Comas are various on the manifestations and pathogenies (mechanisms of an origin of diseases) that causes also different therapeutic tactics at a different origin koma.
In clinical practice the concept of a coma was approved as the menacing state which often has specific staging of the development and which demands urgent diagnosis and therapy when oppression of activity of TsNS did not reach the peak yet. Thus, the clinical diagnosis of a coma is established not only when there are all signs of this state, and even at partial oppression of TsNS if to whom consider as a coma stage. If in the diagnosis other morbid condition of which the loss of consciousness is characteristic is specified, usually the diagnosis of a coma is not selected.
There are over 30 different types of a coma differing on the etiology.
The endocrine coma arises because of disbolism as a result of disturbance of a hormonal background or overdose by drugs with the content of hormones. Sharp increase in concentration of thyroid hormones in blood serum (a coma thyrocardiac), sharp decrease in level of glucose in blood because of the wrong insulin therapy (a hypoglycemic coma) can be an example.
Oppression of a nervous system because of primary damage of a brain is characteristic of primary cerebral coma:
- The coma tumoral arises because of a brain tumor, and also its covers;
- The coma apoplektiformny arises because of secondary disturbance of blood circulation in a brain;
- The meningeal coma usually develops at infectious meningitis as a result of intoxication;
- Apoplectic coma – at acute disorders of blood circulation in a brain;
- The epileptic coma results from an epileptic seizure;
- The coma traumatic, as a rule, is result of an injury.
- The thermal coma – represents a loss of consciousness because of overheating of an organism, it is possible to carry a heatstroke to this type of a coma.
The toxic coma results from various infectious diseases, pancreatitis, toxicoinfections, a renal or liver failure, endogenous intoxication, because of influence of exogenous poison:
- The alcoholic coma arises because of poisoning alcohol influence;
- Coma charcoal – because of poisoning with carbon monoxide;
- The coma barbituric becomes result of poisoning with derivative substances of barbituric acid (luminal, phenobarbital);
- The coma cholera arises because of disturbance of water and electrolytic balance and poisoning with bacterial toxins at cholera;
- The uremic coma is connected with a renal failure;
- Hepatic coma – with hepatic;
- The Iperlaktatsidemichesky or laktatsidotichesky coma arises because of instant increase in blood of lactic acid, usually it is observed at a diabetes mellitus;
- Côme Guiperquetonemitchescaia is the also diabetic coma connected with accumulation of ketonic bodies in an organism (beta and hydroxy-butyric and acetoacetic acids, acetone).
- The coma giperosmolyarny arises because of sharp increase in osmotic pressure. The high hyperglycemia which is often arising at a diabetes mellitus can become the reason.
- The eclamptic coma develops as a result of an eclamptic attack.
The hypoxemic coma is characterized by sharp decrease in cellular respiration because of blocking of separate enzymes or insufficient intake of oxygen. Distinguish:
- Respiratory coma which origin was an insufficiency of external respiration. It develops as a result of oppression of gas exchange in lungs.
- Gipoksemicheskau a coma which is connected with suffocation, a hypobaric anoxemia, that is with disturbance of intake of oxygen from the outside. Also this type of a coma can arise because of heavy disturbance of blood circulation in an organism and disturbance of the movement of oxygen at anemias.
Oppression of work of a brainstem, subcrustal educations and bark which characterizes development of a coma is connected with structural changes in TsNS and metabolic disturbances, their ratios are various at different types of a coma.
Structural disturbances are primary and have a principal value in definition of the mechanism of development of a coma which is caused by inflammatory changes of a brain and its covers, tumoral processes in a brain, disturbance of cerebral circulation or a craniocereberal injury. At infectious intoxication major importance has disturbance of a metabolism.
Studying of secondary injuries of a brain also is of great importance, as well as physical properties of educations in a skull at a coma which was initially caused by disbolism. In the majority of such cases hypostasis of covers of a brain, brain swelling, expansion of perivascular spaces, dot hemorrhages, uneven filling by brain blood takes place. Such changes of a brain, increase in intracranial pressure and other factors aggravate disturbance of a metabolism in nervous cells and promote oppression of their activity.
The pathogeny of a coma which arose because of disbolism, is defined by features of pathological process or a basic disease.
The lack of nutrients, and also disturbance of process of their utilization is a basis of development of a hypoglycemic coma, a hungry coma. These processes also take place at development of a coma because of endocrine disturbances when there is a serious change of a metabolism.
Disturbance of cellular respiration is one of basic reasons of deficit of energy in a brain, about it it is possible to judge by the changed cells, similar vyyalena at a hypoxia were it. Symptoms of dystrophy and acute swelling are found in neurocytes, glybchaty inclusions in cells and other changes are defined. Disturbance of cellular respiration can also arise because of blocking by cytotoxic poisons of respiratory enzymes (at a toxic coma), the terminations of inflow of blood to some sites of a brain or in general, anemia at acute hemolysis, etc. Disorders of microcirculation take place practically in all cases of a coma with a lethal outcome.
Disturbance of a homeostasis of neurocytes is reflected first of all in processes of polarization of membranes, forming of cellular potentials that leads to blockade of receptors, disturbance of formation of mediators, defective bonds between neurons. These processes are shown by loss or oppression of function of structures of TsNS involved in pathological process. Increase in number of these frustration usually is followed by degradation of subcellular structures and serious properties of cells.
Some types of a coma, for example, hepatic or uraemic, develop because of change of water and electrolytic balance which at an early stage of a coma make the main part of its pathogeny, and also accelerate transition to a deep coma. In many cases at a coma expressiveness of oppression of TsNS is proportional to disturbance of water and electrolytic balance. However it does not belong to the coma caused by impact of poisons on a human body.
Development of a coma can happen as gradually (within several hours, days), quickly – within several minutes till 3 o'clock, and almost instantly.
The coma on severity is divided into several levels on severity of a coma.
Prekoma is characterized by the confused consciousness, average degree of an oglushennost, psychomotor excitement or drowsiness, block, psychotic states are possible, at the same time all reflexes remain kept.
For a coma of the first degree the following signs are inherent: the dream, the expressed oglushennost, deferred reaction on strong, including painful, irritants, the patient can independently turn over and eat food, drink, but contact with it is complicated.
The sopor and deep sleep is characteristic of a coma of the second degree, contact with the patient is absent, reaction to pain is weakened, the movements are chaotic, and breath can be pathological, usually with a tendency to hyperventilation, involuntary defecation and an urination are possible. Pupils are usually narrowed, their photoharmose is weakened. Tendon jerks raise, and skin are weakened, the photoharmose remains, the pendulum movements of eyes and slight squint are possible. Corneal and gag reflexes remain, skin are absent, muscular dystonia, sharp change of a muscle tension of extremities develops.
At a coma of the third degree there is no consciousness, corneal reflexes, reaction to pain and to light. Gag reflexes are oppressed, narrowing of a pupil, decrease in a tone of muscles and tendon jerks, arterial pressure, body temperature is quite often observed. For this state involuntary defecation and an urination are also inherent.
Ultraboundary, or the coma of the fourth degree is characterized by full oppression of reflexes, that is the areflexia, strong disturbance of work of a myelencephalon takes place, muscles lose a normal tone, arterial pressure strongly decreases, spontaneous breath stops.
Exit of their coma as a result of therapy is characterized by recovery of work of TsNS, usually upside-down to their oppression. Corneal and pupillary reflexes are at first recovered, vegetative frustration decrease. At recovery of consciousness of the patient passes through an oglushennost, nonsense, hallucinations. Often during an exit from a coma the motive concern, the chaotic movements, convulsive attacks, a twilight state takes place.