toxic shock syndrome (TSS). acute, sometimes fatal, disease characterized by high fever, nausea, diarrhea, lethargy, blotchy rash, and sudden drop in blood pressure. It is caused by Staphylococcus aureus, an exotoxin-producing bacteria (see toxin). Toxic shock was initially identified among menstruating women using high-absorbency tampons that contained synthetic materials, now no longer used, that bound and removed magnesium from the surrounding bodily environment. The resulting lower magnesium levels encouraged bacterial exotoxin production. Slightly more than half of all cases now occur in menstruating women; nonmenstruating women, men, and children may also develop TSS, as a result of infection after surgery and other causes. Treatment mainly involves supportive measures, such as intravenous fluids and, if necessary, kidney dialysis, but may include antibiotics and immunoglobulin.

shock wave, wave formed of a zone of extremely high pressure within a fluid, especially the atmosphere, that propagates through the fluid at a speed in excess of the speed of sound. A shock wave is caused by the sudden, violent disturbance of a fluid, such as that created by a powerful explosion or by the supersonic flow of the fluid over a solid object. Propagating from the point of the disturbance, a shock wave carries energy and can have destructive effects as it impinges on solid objects. A shock wave decays rapidly with increasing distance from its point of origin, gradually changing into an ordinary sound wave. Continuous shock waves, such as those produced by supersonic aircraft, are of particular concern as they tend to recur along regular routes. Even after they have decayed into sound waves, thus losing their destructive force, they remain capable of creating noise levels harmful to human beings and animals.

shock therapy: see electroconvulsive therapy.

shock absorber, device for reducing the effect of a sudden shock by the dissipation of the shock's energy. On an automobile, springs and shock absorbers are mounted between the wheels and the frame. When the wheels hit a hole or a raised spot on a road, the springs absorb the resultant shock by expanding and contracting. To prevent the springs from shaking the frame excessively, their motion is restrained by shock absorbers, which are also known by the more descriptive term dampers. The type of shock absorber found on automobiles is usually a hydraulic type that has a casing consisting of two tubes, one telescoping into the other. In order for a spring to expand and contract, it must pull apart and push together the ends of this shock absorber. But the ends offer so much resistance that the motion of the spring quickly dies out. The ends are connected to a piston in an oil-filled chamber in the shock absorber's inner tube. The piston can only move if it forces oil past it through valves. This arrangement creates a large resistance to any motion by the piston and consequently by the ends. On some automobiles a type of hydraulic suspension is used to function both as a spring and as a shock absorber. It comprises a sealed spherical container filled with equal volumes of hydraulic fluid and gas under pressure. The compression of the gas, which absorbs the shock, is supplied by the vehicle's engine. Shock absorbers are used on aircraft to ease the impact upon landing. Some machines are mounted on resilient materials composed, e.g., of cork or rubber. The materials act as shock absorbers, isolating the vibrations of the machine from the surrounding area.

shock, any condition in which the circulatory system 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. Fainting 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 shock, allergic shock (see anaphylaxis), and emotional shock. See first aid.

insulin shock: see hyperinsulinism.

electric 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 factors as wetness of the skin, area of contact, duration of contact, constitution of the victim, and whether or not the victim is well grounded. The general range of disturbances include a mild tingling (usually produced by common static electricity), spasm of the muscles, loss of consciousness, and sometimes death. In addition, burns occur where the current enters and leaves the body. A lethal dose of electricity may paralyze the respiratory organs and damage the central nervous system; the immediate cause of death, however, is usually an interruption of heart action. Electroconvulsive therapy is the use of electric shock to treat certain mental illnesses.

Bacterial disease caused by a toxin produced by the bacterium Staphylococcus aureus. It was first recognized in 1978 in women using superabsorbent tampons. High fever, diarrhea, vomiting, and rash may progress to abdominal tenderness, drop in blood pressure, shock, respiratory distress, and kidney failure. The syndrome also has other causes, including postsurgical infection. Antibiotics are not effective. With intensive supportive therapy, most patients recover in 7–10 days, but 10–15percnt die. Many patients have a milder recurrence within eight months.

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formerly shock therapy

Method of treating psychiatric disorders by inducing shock through electric current. Electroconvulsive, or electroshock, therapy involves passing an electric current through the patient's head between two electrodes placed over the temples and thus causing a convulsive seizure; it was used to treat bipolar disorder and other types of depression. Shock was previously induced by administering increasingly large doses of insulin until the patient was thrown into a brief coma; the so-called insulin-shock therapy was used for the treatment of schizophrenia. Both forms of shock therapy were developed in the 1930s. Their use declined after the introduction of tranquilizing drugs and antidepressants.

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Device for controlling unwanted motion of a spring-mounted vehicle. On an automobile, the springs act as a cushion between the axles and the body and reduce the shocks produced by a rough road surface. Since some combinations of road surface and car speed may result in excessive up-and-down motion of the car body, shock absorbers—which today are hydraulic devices that oppose both compression and stretching of the springs—slow down and reduce the magnitude of these vibratory motions. Seealso damping.

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State in which the circulatory system fails to supply enough blood to peripheral tissues to meet basic requirements. Symptoms—weak, rapid pulse; low blood pressure; and cold, sweaty skin—are not all present in every case. Causes include low blood volume, caused by bleeding or fluid loss from burns or dehydration; inability of the heart to pump enough blood, due to heart attack, pulmonary embolism, or cardiac tamponade (compression of the heart by fluid in the membrane around it); and blood-vessel dilation as a result of septicemia, allergy (including anaphylaxis), or drugs. All result in reduced capillary blood flow; reflexes increase heart rate and constrict small blood vessels to protect the blood supply to essential organs. Without treatment of the underlying cause, these mechanisms fail; since the cause is not always clear, cases tend to require different and occasionally contradictory treatment (e.g., intravenous fluids can save the life of a patient with massive blood loss but can overload a weakened heart).

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Physical effect of an electric current that enters the body, ranging from a minor static-electricity discharge to a power-line accident or lightning strike but most often resulting from house current. The effects depend on the current (not the voltage), and the worst damage occurs along its path from the entry to the exit point. Causes of immediate death are ventricular fibrillation and paralysis of the brain's breathing centre or of the heart. Cardiopulmonary resuscitation is the best first aid. Though most survivors recover completely, aftereffects may include cataract, angina pectoris, or nervous-system disorders.

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Severe, immediate, potentially fatal bodily reaction to contact with a substance (antigen) to which the individual has previously been exposed. Often triggered by antiserum, antibiotics, or insect stings, the reaction's symptoms include skin flushing, bronchial swelling (with difficulty breathing), and loss of consciousness. Shock may follow. Milder cases may involve hives and severe headache. Treatment, consisting of injection of epinephrine, followed by antihistamines, cortisone, or similar drugs, must begin within minutes. Anaphylaxis may be caused by extremely small amounts of antigen.

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