shock

Definition

Shock is a medical emergency in which the organs and tissues of the body are not receiving an adequate flow of blood. This deprives the organs and tissues of oxygen (carried in the blood) and allows the buildup of waste products. Shock can result in serious damage or even death.

Description

There are three stages of shock: Stage I (also called compensated, or nonprogressive), Stage II (also called decompensated or progressive), and Stage III (also called irreversible).

In Stage I of shock, when low blood flow (perfusion) is first detected, a number of systems are activated in order to maintain/restore perfusion. The result is that the heart beats faster, the blood vessels throughout the body become slightly smaller in diameter, and the kidney works to retain fluid in the circulatory system. All this serves to maximize blood flow to the most important organs and systems in the body. The patient in this stage of shock has very few symptoms, and treatment can completely halt any progression.

In Stage II of shock, these methods of compensation begin to fail. The systems of the body are unable to improve perfusion any longer, and the patient's symptoms reflect that fact. Oxygen deprivation in the brain causes the patient to become confused and disoriented, while oxygen deprivation in the heart may cause chest pain. With quick and appropriate treatment, this stage of shock can be reversed.

In Stage III of shock, the length of time that poor perfusion has existed begins to take a permanent toll on the body's organs and tissues. The heart's functioning continues to spiral downward, and the kidneys usually shut down completely. Cells in organs and tissues throughout the body are injured and dying. The endpoint of Stage III shock is the patient's death.

— Rosalyn Carson-DeWitt, MD

1. 1. A violent collision or impact; a heavy blow. See synonyms at collision.
   2. The effect of such a collision or blow.
2. 1. Something that jars the mind or emotions as if with a violent unexpected blow.
   2. The disturbance of function, equilibrium, or mental faculties caused by such a blow; violent agitation.
3. A severe offense to one's sense of propriety or decency; an outrage.
4. A potentially fatal physiological reaction to a variety of conditions, including illness, injury, hemorrhage, and dehydration, usually characterized by marked loss of blood pressure, diminished blood circulation, and inadequate blood flow to the tissues.
5. The sensation and muscular spasm caused by an electric current passing through the body or a body part.
6. A sudden economic disturbance, such as a rise in the price of a commodity.
7. A shock absorber.

1. To strike with great surprise and emotional disturbance.
2. To strike with disgust; offend.
3. To induce a state of physical shock in (a person).
4. To subject (an animal or person) to an electric shock.

[French choc, from choquer, to collide with, from Old French chuquier, perhaps of Germanic origin.]

1. A number of sheaves of grain stacked upright in a field for drying.
2. A thick heavy mass: a shock of white hair.

[Middle English shok.]

For more information on shock, visit Britannica.com.

Shock has many meanings in common usage. Most often it refers to a sudden mental or emotional experience ranging from a trivial unpleasant surprise to the deep disturbance of personal disaster or bereavement; ‘shell-shock’ refers to distress and disturbed behaviour in the aftermath of battle. When the media report someone as ‘suffering from shock’ this may vaguely imply ‘only’ shock, without physical injury, whereas a clinician will use the term for a potentially dangerous condition with quite specific physical features. This last will be the main topic under this heading.

In medical terms, shock occurs when the blood supply to the tissues is inadequate to meet the requirements of the body. It is a sudden, or acute, failure of the circulation.

Causes of shock

The simplest and most frequent example of acute failure of the circulation is fainting. The cause may be a sudden emotional or painful experience — a physical reaction, linked to a mental ‘shock’ via the autonomic nervous system, which causes slowing of the heart rate. When the heart slows excessively, it does not pump out enough blood and the blood pressure decreases. The person may say that they ‘feel faint’ because they experience dizziness due to the decreased blood pressure and the resulting inadequate blood flow to the brain. If the blood pressure is not restored by, for example, lying down or sitting with the head between the knees, they may lose consciousness. Generally, the heart rate will quickly return to normal and the person awakens with an anxious crowd looking down at them.

Fainting may result also from standing still particularly in very hot conditions. This can cause the blood to collect or ‘pool’ in the lower limbs. Less blood reaches the heart and so less can be pumped out. If the blood pressure decreases excessively, then the patient may faint. Fighter pilots can encounter a similar effect when they make their aircraft turn very tightly at high speed. The high ‘G’ forces cause blood to drain into their lower limbs. They may experience a ‘grey out’ and then a ‘black out’ before losing consciousness as the blood pressure gradually decreases. An anti-gravity suit is designed to maintain pressure on the blood vessels in the lower limbs and so prevent pooling of the blood with the resulting reduction in blood pressure.

A simple faint can be treated by laying the person flat. This will help to restore the blood pressure to normal; consciousness will then return within a short time. More serious causes of shock require appropriate medical treatment.

The clinical picture of shock which is more than a transient faint includes the signs and symptoms of both inadequate circulation and the body's attempt to compensate for this circulatory failure. Reflex responses to reductions in blood pressure act to prevent or minimize the decrease. The heart rate will increase in an attempt to pump out more blood and this can be felt as a rapid pulse rate (although in a simple faint it is initially slow). The blood vessels to the non-vital organs may constrict in an attempt to move blood away from these tissues towards the vital organs. This can be seen as extreme pallor of the skin and may be one of the first signs that a person is about to faint. The pulse is not only rapid but is described as ‘thin’ or ‘thready’. Hormones, such as adrenaline, are released into the blood stream, and sweating, due to autonomic nervous activity can make the patient's skin feel moist to the touch.

Types of shock and their treatment

Hypovolaemic shock follows major blood loss which may be caused by trauma or during surgery. The blood loss can be visible and obvious or may be hidden as occurs in some types of fractures of leg bones or in internal bleeding from abdominal organs. The signs are similar to those in a patient who has fainted, with a low volume pulse and a pale, moist skin. However, the pulse rate will always be rapid in a patient suffering from hypovolaemic shock as the heart attempts to compensate for the low blood pressure.

resuscitation from haemorrhagic shock following blood loss or a major burn requires rapid blood transfusion and/or administration of other intravenous fluids to replace the circulating volume and to ensure the circulation of well oxygenated blood from the lungs to the brain and other vital organs. An intravenous cannula is inserted and fluids are administered directly into the circulation. As well as whole blood, fluid replacement may involve administration of salt fluids, plasma, or artificial substitutes, and concentrated red blood cells. Blood contains many different components including antibodies which require the blood to be ‘cross-matched’ before administration to the patient. There is considerable research directed at producing artificial blood substitutes which can be used without the need for cross-matching. These are designed to be able to transport oxygen efficiently to the tissues with less risk of producing a transfusion reaction and of transferring infection from the donor to the recipient.

Cardiogenic shock A heart attack (myocardial infarction) is usually the result of a blockage of one of the coronary arteries which supply the heart muscle. If the artery is relatively large or supplies a particularly vital part of the heart, the damaged tissue may reduce the ability of the heart to pump blood around the body. If blood supply to the tissues is decreased because of the reduced output from the heart, then the patient may be in cardiogenic shock.

Cardiogenic shock is usually treated in a specialist intensive care unit where the patient's condition can be monitored closely and the appropriate drugs administered. Anaphylactic shock also requires rapid and skilled medical treatment using intravenous fluids and powerful drugs to restore the circulation to normal. Drugs which cause constriction of the blood vessels may be required. However, the major complication of this therapy is that these drugs produce an increase in the work performed by the heart and an increase in the heart's oxygen consumption, with the result that any primary heart disease may be worsened.

Anaphylactic shock can develop as a result of a serious allergy. The allergen causes the release of chemicals within the body which act to make the small arterial blood vessels dilate and to leak fluid from the capillaries into the surrounding tissues. The dilation of the blood vessels has the effect of expanding the capacity of the circulation, whilst leakage of fluid into the tissues reduces the volume of the blood. The net effect is that there is insufficient filling of the circulation and the blood pressure falls. This can cause a major decrease of blood pressure but the person's skin may be flushed and reddened rather than pale. Leakage of fluid into the tissues may cause swelling which may be seen most clearly around the face. Swelling of the vocal cords can reduce or completely block the patient's airway and so prevent them breathing. In a severe case, the condition can be life threatening and immediate medical treatment is required to combat the allergic response and to assist breathing.

Septic shock Some types of very severe infections (sepsis), can release toxins which also cause the small blood vessels to dilate and to leak fluid into the tissues. This septic shock has the same effect as an anaphylactic shock but is preceded by signs of a severe infection and develops much more gradually. The lungs may be badly affected and the leakage of fluid into the lungs can greatly reduce the ability to transfer oxygen into the blood stream.

The mainstay of therapy for any infection and particularly for septic shock is eradication of the infection. Powerful antibiotics are administered according to the specific clinical situation, and any focus of infection or abscess must be drained surgically.

Consequences of severe shock of any type

When the patient's blood pressure decreases, sensors in the blood vessels (baroreceptors) send signals which lead to an increase in heart rate, more powerful beating of the heart, and constriction of the blood vessels supplying the less vital organs. Breathing becomes less effective because blood flow to parts of the lung, and therefore the uptake of oxygen, is inadequate, and the patient may be seen to breathe more heavily. Fluid begins to move into the circulation from the tissues to restore the balance, but this is a relatively slow process.

Some tissues are particularly sensitive to severe shock if it is prolonged. The kidneys can be damaged by insufficient blood flow and the patient may develop acute kidney failure. This can require treatment with an artificial kidney until normal function recovers.

After major shock, respiratory failure can occur and this may require the patient to receive artificial ventilation to maintain sufficient delivery of oxygen to the tissues.

A shock liver syndrome can occur in patients in whom marked reduction in blood pressure has persisted for some hours. This can lead to many complications. For example, the liver is responsible for making components necessary for clotting of the blood and lack of these components causes bleeding spontaneously or from relatively minor injury.

Shock, defined as a failure of the circulation, can therefore range from a simple faint which requires minimal treatment to more serious conditions which require skilled medical and nursing care to treat successfully. The essential feature of shock is an inadequate blood supply to the tissues to meet the requirements for oxygen supply and the removal of waste products of metabolism. Treatment must be rapid to protect organs such as the kidneys, lungs, and liver from damage. The challenge for medical staff is to prevent death from irreversible shock by perfecting in-hospital treatment of the seriously ill. Such optimum care will give these patients a chance to return to functional life.

— Gavin Kenny

See also allergy; autonomic nervous system; blood pressure; blood circulation; fainting; G and G suits; haemorrhage; injury; stress.

A general term for a life-threatening state associated with circulatory collapse. It is brought about by a drop in blood pressure to a level too low to maintain an adequate blood supply to tissues. Someone in shock has cold moist skin, a weak rapid pulse, irregular breathing, dilated pupils, and is distressed, thirsty, and restless. Shock may be induced by many causes. Some, such as dehydration, bleeding and severe injury, may be incurred during exercise; others, such as allergic reactions, may be diet related (see anaphylactic shock).

noun

1. Violent forcible contact between two or more things: bump, collision, concussion, crash, impact, jar, jolt, percussion, smash. See conflict/cooperation.
2. Something that jars the mind or emotions: blow², jolt. Psychiatry trauma. See strike/miss.

verb

1. To deprive of courage or the power to act as a result of fear, anxiety, or disgust: appall, consternate, daunt, dismay, horrify, shake. See fear/courage.
2. To affect with a strong feeling of moral aversion: scandalize. See right/wrong.
3. To inflict physical or mental injury or distress on: traumatize, wound. See help/harm/harmless.
4. To cause to experience a sudden momentary shock: electrify, jolt, startle. See excite/bore/interest, surprise/expect.

noun

A group of things gathered haphazardly: agglomeration, bank¹, cumulus, drift, heap, hill, mass, mess, mound, mountain, pile, stack, tumble. See order/disorder.

Definition: complete surprise; blow
Antonyms: expectation

1. a state of collapse of the body after injury or trauma. Shock may be either primary or secondary. The principal effects of shock are slowing of the peripheral blood flow and reduction in cardiac output. 2. circulatory insufficiency caused by a disparity between circulating blood volume and vascular capacity.

General term for a life-threatening state of weakness brought about by a circulatory disturbance when arterial blood pressure is insufficient to maintain an adequate supply of blood to the tissues. A person in shock has cold moist skin, a weak rapid pulse, irregular breathing, dilated pupils, and is distressed, thirsty, and restless. Shock may be induced by many causes including dehydration, heart attack, bacterial infection, allergic reactions, drug overdose, severe injury, or haemorrhaging.

A condition of acute peripheral circulatory failure due to derangement of circulatory control or loss of circulating fluid. It is marked by hypotension, coldness of the skin and tachycardia.

• allergic s. — see anaphylactic shock.
• s. bodies — hyaline globules composed of fibrin degradation products which act as microthrombi and cause hemorrhage and necrosis.
• burn s. — the loss and redistribution of fluid, electrolytes and plasma protein, increased blood viscosity and increased peripheral resistance that follow a severe burn contribute to shock.
• cardiogenic s. — classically associated with acute myocardial infarction in humans; in animals may be caused by intrinsic congestive heart failure, cardiac depression caused by anesthetic overdosage or other drugs with negative inotropism, rarely, thromboembolism.
• colloidoclastic s. — shock due to breakdown of the physical equilibrium of the body colloids. Thought to cause anaphylactic shock due to the absorption of the colloids into the bloodstream.
• distributive s. — see vasogenic shock (below).
• electric s. — see electrical injuries.
• electroplectic s. — electric shock. See also electrical stunning.
• endotoxic s. — caused by endotoxins, especially Escherichia coli. See also toxemic shock.
• s. gut — animals in shock develop changes in the gut including congestion and hemorrhage into the lumen.
• hypovolemic s. — shock due to reduced blood volume as a result of water deprivation, fluid loss due to diarrhea, vomiting, extensive burns, intestinal obstruction, whole blood loss.
• insulin s. — a condition of circulatory insufficiency resulting from overdosage with insulin, which causes too sudden reduction of blood sugar. It is marked by tremor, weakness, convulsions and collapse.
• irreversible s. — shock which has reached the stage where irreparable damage has been done to tissues, e.g. liver, kidneys and treatment will not salvage the patient although it might prolong life for a long time.
• s. lung — animals in shock due to massive burns, septicemia, disseminated intravascular coagulation (DIC), acute viral or bacterial pneumonias or trauma develop an acute respiratory distress syndrome. The pulmonary lesion is a nonspecific acute or subacute interstitial pneumonia.
• nervous s. — a temporary cessation of function in nervous tissue caused by an acute insult such as trauma without the part having been directly or detectably damaged. The loss of function is only temporary, usually for a few minutes but it may last for several hours. There may be residual signs due to direct damage when the shock passes. Stunning by a lightning stroke is an example.
• s. organs — those organs, specific to each animal species, which respond to allergens circulating in the blood.
• septic s. — see toxemic shock.
• spinal s. — flaccid paralysis up and down the body from the site of the spinal cord lesion. Accompanied by a fall in skin temperature, vasodilatation and sweating. Signs disappear within an hour or two. There may be residual signs due to physical injury to tissue.
• toxic s. — see toxemic shock.
• vasogenic s., vasculogenic s. — shock exists because of the severe reduction in effective circulating blood volume caused by sequestration of blood and other fluids in the vascular system and their withdrawal from the circulating blood. Is the classical shock of traumatic injury, burns, uterine prolapse, extensive surgery.

Dansk (Danish)
1.
n. - chok, rystelse, stød
v. tr. - chokere, ryste
v. intr. - chokere, ryste

idioms:

• shock absorber    støddæmper
• shock horror    skræk og rædsel
• shock tactics    choktaktik
• shock therapy    chokbehandling
• shock treatment    chokbehandling
• shock troops    stormtropper, stødtropper
• shock wave    trykbølge, stødbølge

2.
n. - hob, trave
v. tr. - sætte i hobe, sætte i traver

3.
n. - måtte, manke

Nederlands (Dutch)
schok, schokeffect, schokdemper, schokken, shockeren

Français (French)
1.
n. - choc, (Méd) état de choc
v. tr. - consterner, choquer
v. intr. - se heurter, entrer en collision

idioms:

• shock absorber    amortisseur
• shock horror    horreur, quelle horreur
• shock tactics    (gén, Mil) tactique de choc
• shock therapy    thérapie de choc
• shock treatment    (Psych) traitement par électrochocs, (fig) traitement de choc
• shock troops    troupes de choc
• shock wave    onde de choc

2.
n. - gerbe
v. tr. - mettre en gerbe

3.
n. - tignasse

Deutsch (German)
1.
n. - Schock, Schlag, Erschütterung
v. - schockieren, verstören

idioms:

• shock absorber    Stoßdämpfer
• shock horror    Schreck-, oh Schreck
• shock tactics    (Mil.) taktischer Einsatz von Stoßtruppen
• shock therapy    (Med.) Schocktherapie
• shock treatment    Schockbehandlung
• shock troops    Stoßtruppen
• shock wave    Druckwelle, Stoßwelle

2.
n. - Hocke
v. - Garbenhaufen aufstellen

3.
n. - Schopf

Ελληνική (Greek)
n. - κλονισμός, δόνηση, σοκ, κραδασμός, τράνταγμα, θημωνιά, τούφα μαλλιών, (ιατρ.) καταπληξία, αμορτισέρ
v. - σκανδαλίζω/-ομαι, σοκάρω/-ομαι, καταταράσσω/-ομαι, κλονίζω/-ομαι

idioms:

• shock absorber    απορροφητήρας κραδασμών
• shock horror    οδυνηρή έκπληξη
• shock tactics    αιφνιδιαστικό πλήγμα, τακτική αιφνιδιασμού
• shock therapy    (ιατρ.) θεραπεία με ηλεκτροσόκ
• shock treatment    (ιατρ.) θεραπεία με ηλεκτροσόκ
• shock troops    (στρατ.) δυνάμεις κρούσεως
• shock wave    κρουστικό κύμα

Italiano (Italian)
scuotere, provocare uno shock, scandalizzare, sconvolgere, scossa, shock, scossa elettrica

idioms:

• shock absorber    ammortizzatore
• shock horror    orrore
• shock tactics    tattica d'urto
• shock therapy/treatment    terapia d'urto
• shock troops    truppe d'assalto
• shock wave    onda (d'urto)

Português (Portuguese)
n. - choque (m), descarga elétrica, comoção
v. - chocar, escandalizar

idioms:

• shock horror    medo que algo terrível aconteça
• shock tactics    método de persuasão
• shock therapy/treatment    tratamento doenças mentais
• shock troops    tropas de choque
• shock wave    onda de terror por fato inesperado

Русский (Russian)
удар, толчок, электрический удар, отдача, потрясение, шок, копна, толпа, уйма, копна волос, ударять, шокировать, поражать, вызывать шок, лохматый

idioms:

• shock absorber    амортизатор
• shock horror    пугающий (заголовок в газете), какой кошмар! (иронически)
• shock tactics    тактика сокрушительных ударов, внезапные неожиданные действия
• shock therapy/treatment    шокотерапия
• shock troops    ударные части
• shock wave    взрывная волна

Español (Spanish)
1.
n. - conmoción, golpe, sacudida, sobresalto, impacto, descarga eléctrica, shock, trauma
v. tr. - escandalizar, chocar, conmocionar, horrorizar, sobresaltar, producir un choque nervioso, someter al choque eléctrico, sacudir, conmover
v. intr. - chocar

idioms:

• shock absorber    amortiguador
• shock horror    choque de espanto
• shock tactics    táctica de choque
• shock therapy    terapia por electrochoques
• shock treatment    tratamiento por electrochoques
• shock troops    tropas de choque o de asalto
• shock wave    onda expansiva

2.
n. - hacina, tresnal
v. tr. - hacinar

3.
n. - greña, maraña

Svenska (Swedish)
n. - stöt, törn, chock, slag, sammanstötning, skyl
v. - uppröra, chockera, stöta, väcka anstöt, ge en chock, sätta upp i skylar

中文（简体）(Chinese (Simplified))
1. 冲击, 冲撞, 震惊, 震动, 引起震惊的事件, 使震动, 使受电击, 使休克, 吓人

idioms:

• shock absorber    减震器, 缓冲器
• shock horror    惊恐, 恐怖的, 令人震惊的, 好恐怖!真吓人!
• shock tactics    打击策略, 突击战术, 出人意料的做法
• shock therapy    克疗法, 冲击疗法, 电休克疗法
• shock treatment    电休克疗法
• shock troops    突击队
• shock wave    冲击波, 强烈的反应, 激波, 激烈的动乱

2. 禾束堆, 把...做成禾束堆

中文（繁體）(Chinese (Traditional))
1.
n. - 禾束堆
v. tr. - 把...做成禾束堆

2.
n. - 衝擊, 衝撞, 震驚, 震動, 引起震驚的事件
v. tr. - 使震動, 使受電擊, 使休克
v. intr. - 震動, 嚇人

idioms:

• shock absorber    減震器, 緩衝器
• shock horror    驚恐, 恐怖的, 令人震驚的, 好恐怖!真嚇人!
• shock tactics    打擊策略, 突擊戰術, 出人意料的做法
• shock therapy    克療法, 衝擊療法, 電休克療法
• shock treatment    電休克療法
• shock troops    突擊隊
• shock wave    衝擊波, 強烈的反應, 激波, 激烈的動亂

한국어 (Korean)
1.
n. - 충격, 정신적 타격, 쇼크
v. tr. - ~에 충격을 주다, 격돌하다, 감전시키다
v. intr. - 부딪치다, 놀라다

2.
n. - 볏가리 (벼 따위의 다발을 서로 기대어 세운 것), 옥수수의 더미
v. tr. - 볏단을 가리다, 더미를 쌓다

3.
n. - 부스스 헝클어진 머리, 난발, 푸들 개

日本語 (Japanese)
n. - 衝撃, ショック, 激動, 打撃, ショック状態, 電撃, 感電, もじゃもじゃの髪, 刈束の山, 激突
v. - 衝撃を与える, 憤慨させる, 感電させる

idioms:

• shock absorber    緩衝器, ショックアブソーバー
• shock horror    ショックホラー
• shock tactics    急襲戦術, 急激な行動
• shock therapy/treatment    ショック療法
• shock troops    奇襲部隊
• shock wave    衝撃波, 爆風

العربيه (Arabic)
‏(الاسم) ألسكته ألدماغيه, صدمه, هزة, كومه (فعل) يصدم, يوقع في نفسه ألذعر‏

עברית (Hebrew)
n. - ‮הלם, זעזוע, מכת-חשמל, מנחת-זעזועים, אירוע או חוויה פתאומיים ומזעזעים‬
v. tr. - ‮זעזע, הדהים, הרגיז, הפחיד, העציב, הגעיל‬
v. intr. - ‮חווה זעזוע/הלם‬
n. - ‮ערימת עומרים, אלומות‬
v. tr. - ‮אלם אלומות‬
n. - ‮קווצת שיער פרועה‬

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