From Big Medical Encyclopedia

EXTREME STATES (Latin extremus extreme) — the conditions of an organism which are characterized by the excessive tension or exhaustion of adaptive mechanisms.

The standard definition of the concept «extreme states», objective criteria of their assessment and classification does not exist. AA. pages can initially arise at impact on an organism of various extraordinary irritants (e.g., injuries, exogenous intoxications, sharp fluctuations to a temperat ry air and concentration of oxygen, a hypokinesia, physical overworks) or to be result of the adverse course of the available disease (e.g., circulatory unefficiencies, a respiratory, renal or liver failure, anemia, etc.).

At the heart of development E. pages can lie various pathophysiological mechanisms. The organism can be affected by one or several extreme factors (e.g., intensive exercise stresses in the conditions of highlands and deserts, at space flights, deep-water works etc.), but the maximum tension of adaptive mechanisms arising at the same time prevents life-threatening deviations of parameters of a homeostasis. Such conditions of the maximum tension of adaptive systems of an organism without visible disturbances of the vital functions quite often carry to extreme though in similar cases is older it is possible to speak about extreme living conditions. Extreme tension fiziol. the systems responsible for the emergency adaptation of an organism, it is characteristic, e.g., of the first stage (reaction of tension) stress (see) upon its transition to a stage of exhaustion. In other cases at action on an organism of extraordinary factors ultimate strain of adaptive reactions leads to disturbances in other systems. E.g., at massive to blood loss (see) redistribution of a blood-groove for ensuring satisfactory parameters of the central hemodynamics is followed by sharp restriction of a local renal blood-groove and can cause heavy insufficiency of secretory function of kidneys.

When pathogenicity of an extraordinary irritant exceeds limit opportunities of adaptation of an organism (see. Adaptation ), there are gross violations of vitally important functions and direct threat of death. In such cases there can be a peculiar form E. page — so-called preterminal and terminal states (see).

Many forms E. pages are reversible while terminal states without the special emergency help come to an end with death of an organism. At E. pages are definitely shown properties of the pathogenic factor which caused them and specific mechanisms of development usually enough (e.g., at a traumatic and acute anaphylaxis, a posthemorrhagic collapse); elimination of a pathogenic factor and blockade of the main pathogenetic mechanisms (in particular, a painful afferentation, a toxaemia) can be effective. However in terminal states value of the nature etiol. a factor and specific mechanisms of development of pathology it is rather small. In these cases life of the patient directly depends on a condition of breath and blood circulation, and also on time which passed after their termination.

The most important and often meeting E. pages are collapse (see), shock (see) and coma (see). These states classify depending on caused them etiol. a factor or pathogenetic mechanisms which are the cornerstone of their development. Practically any pathogenic factor causing serious violations of life activity can in the presence of the corresponding conditions lead to developing of a collapse, shock or coma.

Nek-rye E. pages can exist as independently, and to enter as a component in more difficult patol. conditions of an organism (e.g., the collapse can arise at any shock and comas). In such cases usually call a form more general E. page — in the given examples, respectively, shock or a coma. Besides, one E. the page, e.g. a stress in development (from reaction of tension to a stage of exhaustion), can pass into another E. page, e.g. a collapse at a hypokinetic, cold or painful stress.

AA. pages are inherent naturally arising adaptive reactions. In initial stages of development E. page adaptation of an organism to pathogenic influences turns on the mechanisms which are implemented at various levels of the organization. In development E. essential value the activation of sympathoadrenal and pituitary and adrenal systems characteristic of a stress has page. In process of deepening of weight of a state there is a narrowing of range of adaptive reactions, disintegration of the functional systems providing difficult adaptive behavioural acts and thin regulation of locomotory and vegetative functions. One of mechanisms of transition of an organism to extreme forms of adaptation is the progressing disconnection of the central neurons from the various afferentation providing formation difficult functional systems (see). Implementation only of a minimum of afferent signals of elementary forms of breath, blood circulation and some other the vital functions, (generally interoceptive), necessary for implementation, remains; regulation of processes of life activity generally moves to a metabolic level. In this stage, as a rule, there are expressed disturbances of all fiziol. functions.

Characteristic of a pathogeny E. the page is development chain patol. the reactions aggravating emergence of frustration in an organism (see. Circulus vitiosus ). So, at shock disturbance of activity of c. the N of page leads to disturbances of regulation of blood circulation and breath and development hypoxias (see), edges, in turn, deepens disorders of nervous control and a circulatory unefficiency and breath. At a vascular collapse there is a deposition of blood in abdominal organs and reduction of volume of the circulating blood; thereof decrease venous return of blood to heart and cordial emission that leads to further reduction of volume of the circulating blood and weighting of the general state. Similar «vicious circles» arise at the levels of different systems of an organism and at an adverse current patol. process define a tendency E. page to «self-deepening» and transition to a terminal state even after elimination of primary pathogenetic factor.

At all E. pages are observed identical or similar frustration of a metabolism and fiziol. functions, first of all hypoxia. In some cases the hypoxia serves initial etiol. the factor leading to development E. page. Distinguish, e.g., the hypoxemic coma caused by insufficient intake of oxygen from the outside at sharp circulatory disturbances and disturbance of transfer of oxygen blood at heavy anemias and changes of properties of hemoglobin and also at primary disturbances of utilization of oxygen in fabrics. Various forms of initially arising hypoxia can lead also to development of a collapse. However most often the hypoxia arises for the second time at development E. the page caused by any other influence, getting at the same time a role independent, and it is frequent also a decisive pathogenetic factor. At the same time the hypoxia has the mixed character and is caused by various combinations of disorders of breath, blood circulation. conditions of oxygenation of hemoglobin in lungs and its deoxygenation in fabrics. To developing of a secondary hypoxia at E. the page is promoted by damage of the membrane structures providing passive and active transport of substrates and geometrical regularity of the enzymes necessary for normal biological oxidation (see. Membranes biological ).

AA. pages usually are followed by the strengthened release and education histamine (see), serotonin (see), kinin (see), lizosomalny enzymes (see. Lysosomes ) and other physiologically active agents; often the disproteinemia develops, products of a denaturation of protein and disintegration of cells collect. The specified disturbances considerably are characteristic of all E. the page, however their expressiveness and a ratio can significantly differ as at different types E. page, and within each look. So, at many types of a collapse, at burn shock and a dehydrational coma there is dehydration of an organism, a pachemia and increase in an indicator of a hematocrit (see. Gematokritny number ). At the same time at a posthemorrhagic collapse due to transition to a blood channel of an intercellular lymph and a renal delay of water fluidifying of blood and decrease in gematokritny number are observed.

AA. pages are inherent disorders of microcirculation: disturbance of perfusion of microvessels, a trichangiectasia, precapillary sphincters, venules and decrease in their sensitivity to a flowerpot to spring influences. increase in permeability of vascular walls and their structural disturbances up to a necrobiosis. There are a pathological aggregation of erythrocytes, «sladzh-syndrome», (see. Lungs, pathological anatomy ), hypercoagulation of blood, the disseminated intravascular blood coagulation and microthrombosis of vessels (see. Mikrotsirkulyation ).

Disorders of microcirculation in lungs (a so-called «shock lung») can lead to heavy disturbances of their gas exchange function (see Lungs), similar changes in kidneys («a shock kidney») — to renal failure (see). Disturbances of system of microcirculation in a liver and a brain can cause liver failure (see) and sharp disorders of nervous activity.

At all E. pages are observed also disturbances of system hemodynamics (see), characterized by reduction of volume of the circulating blood and speed of a blood-groove, increase in deposition of blood, decrease in venous return of blood to heart, falling of a tone of arterioles and veins up to their paresis and reduction of the general peripheric resistance of a vascular bed. From heart tachycardia, various forms of arrhythmias, insufficiency of a coronary blood-groove, reduction of cordial emission and other signs characteristic are often noted for heart failure (see).

Separate hemodynamic manifestations E. pages can have various expressiveness and the sequence of development. So, for any shock in an initial phase existence of arterial hypertension, is characteristic of a posthemorrhagic collapse — a stage of redistribution of a blood-groove (so-called centralization of blood circulation); at a cardiogenic collapse initially there is a sharp reduction of a stroke output of heart that can bring, despite tachycardia, to falling of the system ABP, and substantial increase of the general peripheric resistance of vessels.

Disturbances of external respiration at E. pages are shown by various changes of its depth and frequency, a rhythm of respiratory movements, a phase ratio of a breath and an exhalation, and also periodic phenomena — so-called wavy breath, periodic breathing like Biota (see. Biotovsky breath ) and Cheyna — Stokes (see. Cheyna — Stokes breath ), breath like Kussmaul (see. Kussmaulya breath ), long inspiratory delays («apneyzis») and others patol. forms of breath.

Disturbances of functions of a nervous system, especially at early stages of development E. pages, are various. So, a peculiar combination of the kept consciousness to the general deep block in a torpid phase is characteristic of the majority of types of shock after the period of the general excitement in an erectile phase. Consciousness is lost only at the end of this phase upon transition to a terminal state. At a collapse consciousness can be kept for a long time; feelings of melancholy, depression and indifference to surrounding are often noted. Development of comas usually begins with emergence of the increasing drowsiness, patients hardly come into adequate contact, consciousness is partially dulled. During the deepening of a coma there is a dead faint and arises total and a reflection in relation to exteroceptive irritations.

AA. villages demand urgent and effective to lay down. actions. Therapy various E. page it is in many respects similar and is defined by a community of pathogenetic mechanisms. However in each case it is necessary to consider an etiology arisen E. page, features of its pathogeny and the nature of the accompanying disturbances.

Depending on a condition of the patient the first urgent measures shall be directed to easing of weight of a hypoxia, and also to elimination of directly life-threatening frustration fiziol. functions. Whenever possible first of all the cause which caused development E is removed. pages, then come to light and interrupted the «vicious circles» promoting aggravation of weight

E. to page and their transition to a terminal state. Along with measures of the general character crucial importance gets intervention in specific pathogenetic mechanisms of separate forms E. page.

Bibliography: Ya. Yu hooks. A water-salt homeostasis at a circulatory unefficiency, L., 1984; Bogolepov N. K. Comas, M., 1962; Bunyatyan A. A., Ryabov G. A. and Manevich A. 3. Anesthesiology and resuscitation, M., 1984; Kryzhanovsky G. N. Determinant structures in pathology of a nervous system. M, 1980; Kulagin V. K. Pathological physiology of an injury and shock, L., 1978; Losev N. I., Hitrov N. K. and Grachev of S. V. Patofiziologiya of hypoxemic states and adaptation of an organism to a hypoxia, M., 1982; Meerson F. 3. Adaptation, stress and prevention, M., 1981; Molchanov N. S. Hypotonic states, L., 1962; Negovsky V. A., etc. Fundamentals of resuscitation, M., 1975; Pathological physiology of extreme states, iod of an edition of P. D. Gorizontov and N. N. Sirotinin. M, 1973; The Guide to cardiology, under the editorship of E. I. Chazov, t. 3, M., 1982; Selye of. Sketches about an adaptation syndrome, the lane with English, M., 1960.

N. I. Losey; S. V. Grachev, N. K. Hitrov.