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any condition in which the circulatory systemcirculatory system,
group of organs that transport blood and the substances it carries to and from all parts of the body. The circulatory system can be considered as composed of two parts: the systemic circulation, which serves the body as a whole except for the lungs, and the
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 is unable to provide adequate circulation to the body tissues, also called circulatory failure or circulatory collapse. Shock results in the slowing of vital functions and in severe cases, if untreated, in death. It may be caused by inadequate pumping by the heart, by reduction of the blood volume due to dehydration or to loss of blood or plasma, or by reduced blood pressure resulting from dilation of the blood vessels. Inadequate pumping may occur as a result of various kinds of heart disease. Blood loss may result from injuries or from such internal conditions as bleeding ulcers. Burns produce extensive plasma loss from blood vessels into the burned area; crush injuries may result in loss of blood and plasma into the injured tissues. Dilation of blood vessels may be caused by injury to the nervous system, or by pain or emotional stress. Faintingfainting
or syncope
, temporary loss of consciousness caused by an insufficient supply of oxygen to the brain. It can be concurrent with any serious disease or condition, such as heart failure, hypertension (high blood pressure), arrhythmia, hemorrhage, injury to the
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 is a form of shock brought about by a sudden reduction of the blood supply to the brain. Symptoms of shock include weakness, pallor, cold and moist skin, and thirst. The arterial blood pressure is reduced, the pulse is weak and rapid, and the surface veins of the limbs may collapse. Emergency aid for shock victims includes maintaining a clear breathing passage, administering oxygen, controlling bleeding, and keeping the patient warm and in a supine position with legs elevated. Therapy may include blood or plasma transfusion to restore the normal circulation, as well as treatment of the underlying cause of shock. The term shock is also applied to a variety of other conditions such as electric shockelectric shock,
effect of the passage of a current of electricity through the body. Fatality may result from shocks of from 1 to 2 amperes and 500 to 1,000 volts. However, the effect of electric shock on the body depends not only on the strength of the current, but on such
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, allergic shock (see anaphylaxisanaphylaxis
, hypersensitive state that may develop after introduction of a foreign protein or other antigen into the body tissues. When an anaphylactic state exists, a second dose of the same protein (commonly an antibiotic such as penicillin, or certain insect venoms) will
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), and emotional shock. See first aidfirst aid,
immediate and temporary treatment of a victim of sudden illness or injury while awaiting the arrival of medical aid. Proper early measures may be instrumental in saving life and ensuring a better and more rapid recovery.
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a packed conical pile of hay or straw, usually put together where the harvesting takes place. The hay is collected from the fellings when they have a moisture content of 25 to 40 percent and is dried completely in shocks over a period of two to three days. Then the hay shocks are stacked into ricks in the open field, under an awning, or in a barn. About 0.75–2 centners are used to make a rick in areas with a damp climate, and about 2.5–4 centners in dry areas. Hay bucks and harvester-stackers are used to collect the hay into shocks. Gathering straw into a shock is done simultaneously with the combine harvesting of cereals; for this operation the combines are equipped with straw collectors.



a sudden life-threatening condition resulting from severe injury and characterized by progressive impairment of all the physiological systems of the body. The main characteristic of shock is the failure of capillary circulation in the tissues owing to impairment of cardiac output and arterial and venous tonus, capillary dysfunction, and changes in the rheological properties of blood. Shock can be brought on by an injury, burns, surgery (traumatic shock, burn shock, surgical shock), incompatible blood transfusion (hemolytic shock), anaphylaxis (anaphylactic shock), functional cardiac disorders (cardiogenic shock), ischemia of tissues and organs, and excessive loss of blood. The condition was described in detail by the French surgeon H. F. Ledran (1737) and by the Russian physician N. I. Pirogov (1870), who described the symptoms of the erectile phase (brief transient excitement) and torpid phase (subsequent sharp functional inhibition) of shock. The clinical manifestations of shock vary considerably. Progressively increasing extreme weakness and a progressive drop in blood pressure are the most characteristic.

Many aspects of the mechanisms underlying the development of shock still remain unclear. From the neuroreflex viewpoint, the various dysfunctions are due to numerous pain impulses that produce sharp excitation and subsequent inhibition of the nervous system, including the vital centers of the medulla oblongata. From the hemodynamic viewpoint, the decrease in the volume of circulating blood, which leads to peripheral circulatory insufficiency, is the principal factor. From the toxemic viewpoint, shock is caused by the entry into the blood of biologically active substances of tissue origin that interfere with the local and systemic blood flow. It is reasonable to assume that each of these factors plays a part: the primary abrupt activation of the central nervous system by extreme nerve impulses (or toxic substances) increases the amount of catecholamines released into the blood, causing a redistribution of the volume of circulating blood—spasms of the blood vessels of the skin, muscles, kidneys, and abdominal cavity accompanied by the increased flow of blood through arteriovenous anastomoses with maintenance of the circulation in the heart and brain (centralization of the circulation). This period of shock is clinically manifested by pallor and clamminess of the skin, contraction of the pupils, cold perspiration on the face, decreased urine flow, and moderately rapid breathing. The blood pressure is normal or slightly lowered.

“Centralization” of the circulation under conditions of extremely severe and prolonged injury becomes the principal mechanism of circulatory failure and further aggravation of the patient’s condition. The decreased flow of blood to the tissues leads to the accumulation of the products of anaerobic metabolism, biogenic amines, kinins, and other substances. Upon entering the bloodstream, these products, along with other humoral factors, such as increased concentration of some hormones and reduced partial pressure of oxygen, further disrupt the regulatory functions of the nervous system.

The chief factors in the pathogenesis of shock in its late stages are hypoxia, decreased vascular tonus, dysfunction of the tissue microcirculation, and gross derangement of cell metabolism, which results in injury to the cell membranes. The transfer of intravascular fluid to the tissues causes a decrease in the volume of circulating blood. This stage is marked by cyanosis, rapid pulse, lowered blood pressure, and dilatation and slow reaction of the pupils.

The subsequent stage of shock is complicated by congestion in small blood vessels, intravascular agglutination of the erythrocytes, decreased blood flow to the heart, acute cardiac insufficiency, and functional impairment of the vital organs. This stage is clinically manifested by gray cyanosis, thready pulse, abrupt drop in blood pressure, rapid, shallow breathing, dilatation of the pupils, and unconsciousness.

In cases of shock, emergency therapeutic measures are undertaken, chosen according to the cause of the shock, stage of its development, and severity of the patient’s condition. Other measures include the administration of pain relievers, keeping the patient warm, the transfusion of blood and blood substitutes, the administration of oxygen, and the injection of hormones, vitamins, and cardiovascular and other agents.

The term “shock” is also applied to persons in an unusual mental state or persons with severe emotional disturbances (mental, or emotional, shock).


“Problemy reaktivnosti i shoka.” Trudy 1-i Vsesoiuznoi konferentsii patofiziologov. Moscow, 1952.
Petrov, I. R., and G. Sh. Vasadze. Neobratimye izmeneniia pri shoke i krovopotere. Leningrad, 1966.
Weil, M. H., and H. Shubin. Moscow, 1971. Diagnostika i lechenie shoka. (Translated from English.)
Cannon, W. B. Traumatic Shock. New York-London, 1923.
Shires, G. T. Shock. Philadelphia, 1973.



A pulse or transient motion or force lasting thousandths to tenths of a second which is capable of exciting mechanical resonances; for example, a blast produced by explosives.
Clinical manifestations of circulatory insufficiency, including hypotension, weak pulse, tachycardia, pallor, and diminished urinary output.


Pathol a state of bodily collapse or near collapse caused by circulatory failure or sudden lowering of the blood pressure, as from severe bleeding, burns, fright, etc.
References in periodicals archive ?
In the study, researchers randomly divided participants into two groups, those who had the shock turned off and those who had the shock replaced by a neutral tone.
Oil price shocks affect the economy primarily through consumers' and firms' spending (Hamilton 2008).
A central premise of our research program is that measuring and modeling shocks at the micro level (to firms and sectors) is essential for understanding the macro consequences of globalization.
In a paper published September 21 in Physical Review Letters, Turok and Ue-Li Pen of the Canadian Institute for Theoretical Astrophysics in Toronto performed calculations and simulations that indicate shocks would have formed less than one ten-thousandth of a second after the Big Bang.
Households in developing countries are frequently hit by severe idiosyncratic shocks and covariate shocks which result in welfare loss not only directly but also as a consequence of the costly measures used by households to protect consumption from such shocks including less risky but also less profitable agricultural investment [Fafchamps (2009)].
For each trial, they had to choose between different amounts of money for different numbers of shocks, up to a maximum 20 shocks and u20 per trial.
Diane Zimberoff and David Hartman; OVERCOMING SHOCK; New Horizon Press (Nonfiction: Self-Help) 15.95 ISBN: 9780882824802
While most ICD-delivered shocks are needed, previous studies estimated that approximately 20 percent of patients with ICDs may experience inappropriate shocks in response to benign arrhythmias or electrical noises sensed by their devices.
Author also examined responses of the term premia to the different shocks. Fendel (2009) intended to support the empirical findings on the information content of the term structure of interest rates for monetary policy.
The winner will get a full set of front and rear Bilstein 5100 shocks for any applicable truck, including Bilstein's 5100 series leveling shocks available for certain trucks.
If your unit has up-armored M915A3 trucks, you may have already noticed that the front shocks, NSN 2510-01-479-1515, don't handle the added weight of the armor too well.
Sam Moore's column on corn shock tiers (February 2011) brought back memories.