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.
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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.
* 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.
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.
- 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.
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 blood vessels.
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.
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.
The Virtual Hospital posts information on shock based on the
University of Iowa Family Practice Handbook,
3rd edition, at