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

Shock

Definition

Shock occurs when the body's organs and tissues do not receive an adequate flow of blood . Inadequate blood flow deprives the organs and tissues of oxygen and allows the buildup of waste products. Shock is a medical emergency and 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 or 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. A person in this stage of shock has very few symptoms, and treatment can completely halt any progression.

In Stage II of shock, the body's standard methods of compensation begin to fail and are unable to improve perfusion any longer. Oxygen deprivation in the brain causes the person 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 death.

Causes and symptoms

Shock is caused by three major categories of problems: cardiogenic (problems associated with the heart's functioning); hypovolemic (total volume of blood available to circulate is low); and septic shock (overwhelming infection , usually by bacteria ).

Cardiogenic shock can be caused by any disease or event which prevents the heart muscle from pumping strongly and consistently enough to circulate the blood in a normal fashion. Heart attack, conditions which cause inflammation of the heart muscle (myocarditis), disturbances of the electrical rhythm of the heart, and any kind of mass or fluid accumulation or blood clot which interferes with flow out of the heart can significantly affect the heart's ability to pump a normal quantity of blood.

Hypovolemic shock occurs when the total volume of blood in the body falls well below normal. This can occur when there is excess fluid loss, as in dehydration due to severe vomiting or diarrhea , diseases which cause excess urination (diabetes insipidus, diabetes mellitus , and kidney failure), extensive burns , blockage in the intestine, inflammation of the pancreas (pancreatitis ), or severe bleeding of any kind.

Septic shock can occur when an untreated or inadequately treated infection (usually bacterial) is allowed to progress. Bacteria often produce poisonous chemicals (toxins) which can cause injury throughout the body. When large quantities of these bacteria and their toxins begin circulating in the bloodstream, every organ and tissue is at risk of their damaging effects. The most damaging consequences include poor functioning of the heart muscle; widening of the diameter of the blood vessels; a drop in blood pressure ; activation of the blood clotting system, causing blood clots, followed by a risk of uncontrollable bleeding; damage to the lungs , causing acute respiratory distress syndrome ; liver failure; kidney failure; and coma .

Initial symptoms of shock include cold, clammy hands and feet; pale or blue-tinged skin tone; weak, fast pulse rate; fast rate of breathing; low blood pressure. A variety of other symptoms may be present, but they are dependent on the underlying cause of shock.

Diagnosis

Diagnosis of shock is based on a person's symptoms, as well as criteria including a significant drop in blood pressure, extremely low urine output, and blood tests that reveal overly acidic blood with a low circulating concentration of carbon dioxide. Other tests are performed, as appropriate, to try to determine the underlying condition responsible for an individual's state of shock.

Treatment

The most important goals in treating shock include quickly diagnosing a person's state of shock; quickly intervening to halt the underlying condition (stopping bleeding, re-starting the heart, giving antibiotics to combat an infection, etc.); treating the effects of shock (low oxygen, increased acid in the blood, activation of the blood clotting system); and supporting vital functions (blood pressure, urine flow, heart function).

Treatment includes keeping a person warm, with legs raised and head down to improve blood flow to the brain, putting a needle in a vein in order to give fluids or blood transfusions, as necessary; giving a person extra oxygen to breathe and medications to improve the heart's functioning; and treating the underlying condition which led to shock.

KEY TERMS

Cardiogenic —Originating with the heart.

Deprivation —A condition of having too little of something.

Hypovolemic —Having a low volume.

Perfusion —Blood flow through an organ or tissue.

Sepsis —An overwhelming infection throughout the body, usually caused by bacteria in the bloodstream.

Prognosis

The prognosis of an individual in shock depends on the stage of shock when treatment was begun, the under-lying condition causing shock, and the general medical state of the person.

Health care team roles

First aid is often given by appropriately trained individuals. Physicians supervise the treatment of shock in a hospital setting. Nurses provide bedside management and patient-family education.

Prevention

The most preventable type of shock is caused by dehydration during illnesses with severe vomiting or diarrhea. Shock can be avoided by recognizing that a person who is unable to drink in order to replace lost fluids needs to be given fluids intravenously (through a needle in a vein). Other types of shock are only preventable insofar as one can prevent their underlying conditions or can monitor and manage those conditions well enough so that they never progress to the point of shock.

Resources

BOOKS

Beebe, Richard W.O., and Deborah L. Funk. Fundamentals of Emergency Care. Albany: Delmar Publishers, 2001.

Evans, Thomas J. Septic Shock: Methods and Protocols. Totowa, NJ: Humana Press, 2000.

Frankel, Lorry, and Lawrence Mathers. "Shock." In Nelson Textbook of Pediatrics. 16th ed. Ed. Richard E. Behrman, et al. Philadelphia: Saunders, 2000, pp.262-266.

Hollengerg, Steven M., and Joseph E. Parrillo. "Shock." In Harrison's Principles of Internal Medicine. 14th ed. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1998, pp.214-222.

Holmes, D. R. "Cardiogenic Shock." In Cecil Textbook of Medicine. 21st ed. Ed. Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp.502-507.

Parrillo, Joseph E. "Approach to the Patient with Shock." In Cecil Textbook of Medicine. 21st ed. Ed. Lee Goldman and Claude J. Bennett. Philadelphia: W.B. Saunders, 2000, pp.495-502.

Parrillo, Joseph E. "Shock syndromes related to sepsis." In Cecil Textbook of Medicine, 21st ed., edited by Goldman, Lee and Bennett, J. Claude. Philadelphia: W.B. Saunders, 2000, pp.507-512.

Rosen, Peter, and Theodore Chan. Atlas of Emergency Procedures. St. Louis: Mosby, 2001.

PERIODICALS

Bernstein, J, and K. Frush. "An Unusual Presentation of Shock in a Previously Healthy Child. Pediatric Emergency Care 17, no. 2 (2001): 107-109.

Briegel, J. "Hydrocortisone and the Reduction of Vasopressors in Septic Shock: Therapy or Only Chart Cosmetics?" Intensive Care Medicine 26, no. 12 (2000): 1723-1726.

Giesbrecht, G. G. "Prehospital Treatment of Hypothermia." Wilderness Environmental Medicine 12, no. 1 (2001): 24-31.

Kaplan L. J., et al. "Start with a Subjective Assessment of Skin Temperature to Identify Hypoperfusion in intensive Care Unit Patients." Journal of Trauma 50, no. 4 (2001): 620-627.

Oppert, M., et al. "Plasma Cortisol Levels Before and During "Low-Dose" Hydrocortisone Therapy and Their Relationship to Hemodynamic Improvement in Patients with Septic Shock." Intensive Care Medicine 26, no. 12(2000): 1747-1755.

Schaffartzik, W., et al. "Different Dosages of Dobutamine in Septic Shock Patients: Determining Oxygen Consumption with a Metabolic Monitor Integrated in a Ventilator." Intensive Care Medicine 26, no. 12 (2000): 1740-1746.

Venkatesh B., et al. "Monitoring Tissue Oxygenation during Resuscitation of Major Burns." Journal of Trauma 50, no. 3 (2001): 485-494.

ORGANIZATIONS

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. <http://www.aaem.org/>.

OTHER

Stevens, Dennis L. "Streptococcal Toxic-Shock Syndrome: Spectrum of Disease, Pathogenesis, and New Concepts in Treatment." Centers for Disease Control and Prevention. <http://www.cdc.gov/ncidod/eid/vol1no3/stevens.htm>. (August 14, 2001).

L. Fleming Fallon, Jr., MD, DrPH

Shock

Definition

Shock occurs when the body's organs and tissues do not receive an adequate flow of blood. Inadequate blood flow deprives the organs and tissues of oxygen and allows the buildup of waste products. Shock is a medical emergency and 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 or 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. A person in this stage of shock has very few symptoms, and treatment can completely halt any progression.

In Stage II of shock, the body's standard methods of compensation begin to fail and are unable to improve perfusion any longer. Oxygen deprivation in the brain causes the person 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 death.

Causes and symptoms

Shock is caused by three major categories of problems: cardiogenic (problems associated with the heart's functioning); hypovolemic (total volume of blood available to circulate is low); and septic shock (overwhelming infection, usually by bacteria ).

Cardiogenic shock can be caused by any disease or event which prevents the heart muscle from pumping strongly and consistently enough to circulate the blood in a normal fashion. Heart attack, conditions which cause inflammation of the heart muscle (myocarditis), disturbances of the electrical rhythm of the heart, and any kind of mass or fluid accumulation or blood clot which interferes with flow out of the heart can significantly affect the heart's ability to pump a normal quantity of blood.

Hypovolemic shock occurs when the total volume of blood in the body falls well below normal. This can occur when there is excess fluid loss, as in dehydration due to severe vomiting or diarrhea, diseases which cause excess urination (diabetes insipidus, diabetes mellitus, and kidney failure), extensive burns, blockage in the intestine, inflammation of the pancreas (pancreatitis), or severe bleeding of any kind.

Septic shock can occur when an untreated or inadequately treated infection (usually bacterial) is allowed to progress. Bacteria often produce poisonous chemicals (toxins) which can cause injury throughout the body. When large quantities of these bacteria and their toxins begin circulating in the bloodstream, every organ and tissue is at risk of their damaging effects. The most damaging consequences include poor functioning of the heart muscle; widening of the diameter of the blood vessels; a drop in blood pressure; activation of the blood clotting system, causing blood clots, followed by a risk of uncontrollable bleeding; damage to the lungs, causing acute respiratory distress syndrome; liver failure; kidney failure; and coma.

Initial symptoms of shock include cold, clammy hands and feet; pale or blue-tinged skin tone; weak, fast pulse rate; fast rate of breathing; low blood pressure. A variety of other symptoms may be present, but they are dependent on the underlying cause of shock.

Diagnosis

Diagnosis of shock is based on a person's symptoms, as well as criteria including a significant drop in blood pressure, extremely low urine output, and blood tests that reveal overly acidic blood with a low circulating concentration of carbon dioxide. Other tests are performed, as appropriate, to try to determine the underlying condition responsible for an individual's state of shock.

Treatment

The most important goals in treating shock include quickly diagnosing a person's state of shock; quickly intervening to halt the underlying condition (stopping bleeding, re-starting the heart, giving antibiotics to combat an infection, etc.); treating the effects of shock (low oxygen, increased acid in the blood, activation of the blood clotting system); and supporting vital functions (blood pressure, urine flow, heart function).

Treatment includes keeping a person warm, with legs raised and head down to improve blood flow to the brain, putting a needle in a vein in order to give fluids or blood transfusions, as necessary; giving a person extra oxygen to breathe and medications to improve the heart's functioning; and treating the underlying condition which led to shock.

Prognosis

The prognosis of an individual in shock depends on the stage of shock when treatment was begun, the underlying condition causing shock, and the general medical state of the person.

Health care team roles

First aid is often given by appropriately trained individuals. Physicians supervise the treatment of shock in a hospital setting. Nurses provide bedside management and patient-family education.

Prevention

The most preventable type of shock is caused by dehydration during illnesses with severe vomiting or diarrhea. Shock can be avoided by recognizing that a person who is unable to drink in order to replace lost fluids needs to be given fluids intravenously (through a needle in a vein). Other types of shock are only preventable insofar as one can prevent their underlying conditions or can monitor and manage those conditions well enough so that they never progress to the point of shock.

KEY TERMS

Cardiogenic— Originating with the heart.

Deprivation— A condition of having too little of something.

Hypovolemic— Having a low volume.

Perfusion— Blood flow through an organ or tissue.

Sepsis— An overwhelming infection throughout the body, usually caused by bacteria in the bloodstream.

Resources

BOOKS

Beebe, Richard W. O., and Deborah L. Funk. Fundamentals of Emergency Care. Albany: Delmar Publishers, 2001.

Evans, Thomas J. Septic Shock: Methods and Protocols. Totowa, NJ: Humana Press, 2000.

Frankel, Lorry, and Lawrence Mathers. "Shock." In Nelson Textbook of Pediatrics. 16th ed. Ed. Richard E. Behrman, et al. Philadelphia: Saunders, 2000: pp.262-266.

Hollengerg, Steven M., and Joseph E. Parrillo. "Shock." In Harrison's Principles of Internal Medicine. 14th ed. Ed. Anthony S. Fauci et al. New York: McGraw-Hill, 1998, pp.214-222.

Holmes, D. R. "Cardiogenic Shock." In Cecil Textbook of Medicine. 21st ed. Ed. Lee Goldman and J. Claude Bennett. Philadelphia: W. B. Saunders, 2000, pp.502-507.

Parrillo, Joseph E. "Approach to the Patient with Shock." In Cecil Textbook of Medicine. 21st ed. Ed. Lee Goldman and Claude J. Bennett. Philadelphia: W. B. Saunders, 2000, pp.495-502.

Parrillo, Joseph E. "Shock syndromes related to sepsis." In Cecil Textbook of Medicine, 21st ed., edited by Goldman, Lee and Bennett, J. Claude. Philadelphia: W. B. Saunders, 2000, pp.507-512.

Rosen, Peter, and Theodore Chan. Atlas of Emergency Procedures. St. Louis: Mosby, 2001.

PERIODICALS

Bernstein, J, and K. Frush. "An Unusual Presentation of Shock in a Previously Healthy Child. Pediatric Emergency Care 17, no. 2 (2001): 107-109.

Briegel, J. "Hydrocortisone and the Reduction of Vasopressors in Septic Shock: Therapy or Only Chart Cosmetics?" Intensive Care Medicine 26, no. 12 (2000): 1723-1726.

Giesbrecht, G. G. "Prehospital Treatment of Hypothermia." Wilderness Environmental Medicine 12, no. 1(2001): 24-31.

Kaplan L. J., et al. "Start with a Subjective Assessment of Skin Temperature to Identify Hypoperfusion in intensive Care Unit Patients." Journal of Trauma 50, no. 4 (2001): 620-627.

Oppert, M., et al. "Plasma Cortisol Levels Before and During "Low-Dose" Hydrocortisone Therapy and Their Relationship to Hemodynamic Improvement in Patients with Septic Shock." Intensive Care Medicine 26, no. 12 (2000): 1747-1755.

Schaffartzik, W., et al. "Different Dosages of Dobutamine in Septic Shock Patients: Determining Oxygen Consumption with a Metabolic Monitor Integrated in a Ventilator." Intensive Care Medicine 26, no. 12 (2000): 1740-1746.

Venkatesh B., et al. "Monitoring Tissue Oxygenation during Resuscitation of Major Burns." Journal of Trauma 50, no. 3 (2001): 485-494.

ORGANIZATIONS

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. (800) 884-2236. 〈http://www.aaem.org/〉.

OTHER

Stevens, Dennis L. "Streptococcal Toxic-Shock Syndrome: Spectrum of Disease, Pathogenesis, and New Concepts in Treatment." Centers for Disease Control and Prevention. 〈http://www.cdc.gov/ncidod/eid/vol1no3/stevens.htm〉. (August 14, 2001).

Shock

What Is Shock?

What Causes Shock?

What Is Septic Shock?

What Is Anaphylactic Shock?

What Are the Symptoms of Shock?

How Is Shock Treated?

How Can Shock Be Prevented?

Resource

Shock is a dangerous physical condition in which the flow of blood throughout the body is drastically reduced, causing weakness, confusion, or loss of consciousness. It can result from many kinds of serious injuries and illnesses. If shock is not treated quickly, a person can suffer permanent organ damage and die.

KEYWORD

for searching the Internet and other reference sources

Circulatory system

What Is Shock?

“I studied for days, but I failed the test. I’m in shock,” says one teenager to another.

In everyday speech, “shock” is common and sometimes even fun. People line up to get shocked by horror movies. They want to feel an emotional jolt from seeing something sudden, surprising, and scary. Their hearts may beat a little faster for a moment, but when the movie ends they’re as healthy as before.

This kind of emotional shock has nothing to do with medical shock. “Shock” in the medical sense also can be sudden, surprising, and scary. But it is a very specific physical condition that is extremely serious.

Shock occurs when the amount of blood reaching the brain and other parts of the body is reduced drastically; in other words, when the blood pressure falls very low. Since the blood carries oxygen needed by every cell in the body, the drop in blood flow deprives the cells of oxygen. The brain, the biggest user of oxygen, is affected, making the person confused, dazed, or unconscious. As cells struggle to function without enough oxygen, many chemical processes in the body are disrupted. Organs, including the lungs, kidneys, liver, and heart, start to fail. Unless the blood flow is restored quickly, the damage may be fatal.

What Causes Shock?

There are several underlying causes of shock. Often, a case of shock involves two or all three of these types of underlying problems. These include:

• There is not enough fluid in the bloodstream. This kind of shock is called hypovolemic (hy-po-vo-LEEM-ik) shock. It can be caused by heavy bleeding from an injury, such as a gunshot wound or wounds suffered in a car crash. It also can be caused by severe bleeding from a medical condition, such as an aortic aneurysm* or bleeding stomach ulcers. It can also occur if a person loses large amounts of fluids other than blood. That can happen, for instance, if a person has severe vomiting and diarrhea or has been badly burned over a large part of the body.

* aortic aneurysm

(ay-OR-tik AN-yoo-rizm) is a weak spot in the aorta, the body’s largest blood vessel. The weak spot can rupture or break, causing massive internal bleeding.

• The blood vessels dilate (expand) too much. If this happens, blood pressure (the pressure within the blood vessels) can become so low that not enough blood is pushed out to reach vital tissues. The most common example of this kind of shock is septic (SEP-tik) shock, which is caused by a severe bacterial infection.
• The heart fails to pump the blood strongly enough. This is called cardiogenic (kar-dee-o-GEN-ik) shock. It can be caused by many heart problems including a heart attack, an abnormal heart rhythm, a blood clot in the heart, or a buildup of fluid around the heart that presses on the organ, or by severe damage to a heart valve.

Electrical Shock

An electric current that passes through the body is called a shock. Although it can also be dangerous (electrical accidents kill about 1,000 people a year in the United States), electrical shock is different from the medical shock discussed in this article.

Medical shock is a reduction in blood flow. Electrical shock primarily causes internal burns and disruption of heart rhythms. Sometimes, however, an electrical shock can cause medical shock. This can happen if the burns lead to rapid loss of fluid and the heart problems prevent adequate pumping of blood.

What Is Septic Shock?

Septic shock occurs when a person is infected with bacteria that get into the bloodstream and produce a dangerous level of toxins (poisons). Even when treated, it is sometimes fatal.

It is most likely to occur in hospitalized people who have recently had surgery or who have had drainage tubes, breathing tubes, or other devices inserted into their body. Such devices increase the chances that bacteria will get into the bloodstream.

Other people at risk for septic shock are those with weakened immune systems, including those who have diabetes, cirrhosis, leukemia, or AIDS. Newborns and pregnant women are also at risk.

Toxic shock syndrome is a form of septic shock that originally was linked to use of certain tampons.

What Is Anaphylactic Shock?

Anaphylactic (an-a-fi-LAK-tik) shock is a severe allergic reaction in which fluid leaks out from the blood vessels and the blood vessels dilate as well. In certain people, it can occur as a reaction to medication, blood transfusions, bee stings, or peanuts or other foods. It can be fatal.

What Are the Symptoms of Shock?

Whatever its cause, people with shock have rapid and shallow breathing, cold and clammy skin, a weak but rapid pulse, low blood pressure, and weakness all over the body. They are dizzy, confused, and may become unconscious.

How Is Shock Treated?

People in shock should be taken by ambulance to a hospital as quickly as possible. Until then, they should be kept lying down on their back with their feet raised about a foot higher than their head. This helps get the blood flowing to the brain and heart. They should be covered with a coat or blankets to keep them warm.

Medical workers will try to raise the blood pressure by giving fluids intravenously (through a needle into a vein). If the shock was caused by blood loss, a blood transfusion may be necessary as well. If the blood pressure still remains dangerously low, drugs known as pressors may be used to raise the blood pressure. For anaphylactic shock, doctors give the drug epinephrine (ep-i-NEF-rin), also called adrenaline, to constrict (narrow) the bloodvessels.

Oxygen is routinely given, and some people need to be put on a ventilator (a breathing machine) to increase the amount of oxygen getting to their cells. If septic shock is suspected, antibiotics are given intravenously.

Once the person is out of immediate danger, doctors can try to treat the underlying causes.

How Can Shock Be Prevented?

Following safety rules to prevent fires and serious accidents, including car crashes, would prevent many cases of shock. To prevent bacterial infections that can cause septic shock, hospitals have rules about sterilizing equipment and washing hands. To prevent anaphylactic shock, people with allergies need to carefully avoid the substances that trigger them.

See also

Heart Disease

Toxic Shock Syndrome

Resource

Organization

The Virtual Hospital posts information on shock based on the University of Iowa Family Practice Handbook, 3rd edition, at http://www.vh.org/Providers/ClinRef/FPHandbook/Chapter01/18-html.

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.

Causes and symptoms

Shock is caused by three major categories of problems: cardiogenic (meaning problems associated with the heart's functioning); hypovolemic (meaning that the total volume of blood available to circulate is low); and septic shock (caused by overwhelming infection, usually by bacteria).

Cardiogenic shock can be caused by any disease, or event, which prevents the heart muscle from pumping strongly and consistently enough to circulate the blood normally. Heart attack, conditions which cause inflammation of the heart muscle (myocarditis), disturbances of the electrical rhythm of the heart, any kind of mass or fluid accumulation and/or blood clot which interferes with flow out of the heart can all significantly affect the heart's ability to adequately pump a normal quantity of blood.

Hypovolemic shock occurs when the total volume of blood in the body falls well below normal. This can occur when there is excess fluid loss, as in dehydration due to severe vomiting or diarrhea, diseases which cause excess urination (diabetes insipidus, diabetes mellitus, and kidney failure), extensive burns, blockage in the intestine, inflammation of the pancreas (pancreatitis ), or severe bleeding of any kind.

Septic shock can occur when an untreated or inadequately treated infection (usually bacterial) is allowed to progress. Bacteria often produce poisonous chemicals (toxins) which can cause injury throughout the body. When large quantities of these bacteria, and their toxins, begin circulating in the bloodstream, every organ and tissue in the body is at risk of their damaging effects. The most damaging consequences of these bacteria and toxins include poor functioning of the heart muscle; widening of the diameter of the blood vessels; a drop in blood pressure; activation of the blood clotting system, causing blood clots, followed by a risk of uncontrollable bleeding; damage to the lungs, causing acute respiratory distress syndrome; liver failure; kidney failure; and coma.

Initial symptoms of shock include cold, clammy hands and feet; pale or blue-tinged skin tone; weak, fast pulse rate; fast rate of breathing; low blood pressure. A variety of other symptoms may be present, but they are dependent on the underlying cause of shock.

Diagnosis

Diagnosis of shock is based on the patient's symptoms, as well as criteria including a significant drop in blood pressure, extremely low urine output, and blood tests that reveal overly acidic blood with a low circulating concentration of carbon dioxide. Other tests are performed, as appropriate, to try to determine the underlying condition responsible for the patient's state of shock.

Treatment

The most important goals in the treatment of shock include: quickly diagnosing the patient's state of shock; quickly intervening to halt the underlying condition (stopping bleeding, re-starting the heart, giving antibiotics to combat an infection, etc.); treating the effects of shock (low oxygen, increased acid in the blood, activation of the blood clotting system); and supporting vital functions (blood pressure, urine flow, heart function).

Treatment includes keeping the patient warm, with legs raised and head down to improve blood flow to the brain, putting a needle in a vein in order to give fluids or blood transfusions, as necessary; giving the patient extra oxygen to breathe and medications to improve the heart's functioning; and treating the underlying condition which led to shock.

Prognosis

The prognosis of an individual patient in shock depends on the stage of shock when treatment was begun, the underlying condition causing shock, and the general medical state of the patient.

Prevention

The most preventable type of shock is caused by dehydration during illnesses with severe vomiting or diarrhea. Shock can be avoided by recognizing that a patient who is unable to drink in order to replace lost fluids needs to be given fluids intravenously (through a needle in a vein). Other types of shock are only preventable insofar as one can prevent their underlying conditions, or can monitor and manage those conditions well enough so that they never progress to the point of shock.

Resources

PERIODICALS

Kerasote, Ted. "After Shock: Recognizing and Treating Shock." Sports Afield 217 (May 1997): 60+.

KEY TERMS

Cardiogenic— Originating with the heart.

Deprivation— A condition of having too little of something.

Hypovolemic— Having a low volume.

Perfusion— Blood flow through an organ or tissue.

Sepsis— An overwhelming infection throughout the body, usually caused by bacteria in the bloodstream.