Shock is a life-threatening condition in which blood flow to the organs is low, decreasing delivery of oxygen and thus causing organ damage and sometimes death. Blood pressure is usually low.
(See also Low Blood Pressure.)
Shock has several causes: Low blood volume, inadequate pumping action of the heart, or excessive widening (dilation) of blood vessels.
When shock is caused by low blood volume or inadequate pumping of the heart, people may feel sluggish, sleepy, or confused, and their skin becomes cold and sweaty and often bluish or pale.
When shock results from excessive dilation of blood vessels, the skin may be warm and flushed, and the pulse may be strong and forceful (bounding) rather than weak.
People who are in shock should be kept warm and positioned so their legs are elevated.
Intravenous fluids, oxygen, and sometimes medications are given to help restore the blood pressure.
Many people who are in shock are brought to emergency departments every day. People go into shock when their blood pressure becomes so low that the body’s cells do not receive enough blood and therefore do not receive enough oxygen. As a result, cells in numerous organs, including the brain, kidneys, liver, and heart, stop functioning normally. If blood flow (perfusion) to these cells is not quickly restored, they become irreversibly damaged and die. If enough cells are damaged or dead, the organ they are in may fail and the person may die.
Multiple organ dysfunction syndrome (MODS) is the failure of 2 or more organs. This diagnosis carries a significant chance of death.
People in shock require immediate emergency treatment and are usually cared for in the hospital intensive care unit.
Did You Know...
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Although low blood pressure is generally the cause of shock, blood pressure may not be low in the early stages of shock. Also, blood pressure can be low in people who do not have shock.
The medical disorder of shock has nothing to do with the “shock” that people feel from a sudden emotional stress.
Causes of Shock
Shock has several causes:
Low blood volume (hypovolemic shock)
Inadequate pumping action of the heart (cardiogenic shock)
Excessive widening of blood vessels (distributive shock)
Did You Know...
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Hypovolemic shock
Low blood volume results in less-than-normal amounts of blood entering the heart with every heartbeat and therefore less-than-normal amounts of blood being pumped out to the body and its cells.
Blood volume may be low because of
Severe bleeding
Excessive loss of body fluids
Inadequate fluid intake (less common)
Blood may be rapidly lost because of
External bleeding, such as that caused by an injury
Internal bleeding, such as that caused by an ulcer in the stomach or intestine (gastrointestinal bleeding), a ruptured blood vessel, or a ruptured ectopic pregnancy (a pregnancy outside the uterus)
An excessive loss of body fluids other than blood can result from
Severe burns
Inflammation of the pancreas (pancreatitis)
Perforation of the intestinal wall
Some kidney disorders
Excessive use of diuretics, which increase the output of urine
Untreated diabetes
Fluid intake may be inadequate because a physical disability (such as severe joint disease) or a mental disability (such as Alzheimer disease) may prevent people from obtaining enough fluids even though they may feel thirsty.
Cardiogenic shock
Inadequate pumping action of the heart can also result in less-than-normal amounts of blood being pumped out with every heartbeat. The most common causes of inadequate pumping action are
A blood clot in the lungs (pulmonary embolism)
Sudden malfunction of a heart valve (particularly an artificial valve)
An abnormal heart rhythm (arrhythmia)
Infections of the heart muscle (myocarditis) or the heart valves (endocarditis)
Inability of the heart to fill due to sudden buildup of fluid in the sac that surrounds the heart (cardiac tamponade)
Other disorders affecting the structure of the heart, for example, rupture of the wall of the heart (myocardial rupture)
Distributive shock
Excessive dilation of blood vessels (vasodilation) increases the capacity of blood vessels and decreases blood pressure. This can decrease blood flow and oxygen delivery to organs.
Blood vessels may be excessively dilated because of
A serious allergic reaction (anaphylaxis or anaphylactic shock)
A severe bacterial infection (shock caused by such an infection is called septic shock or toxic shock)
Overdose of illicit drugs or poisons that dilate blood vessels
Injuries to the spinal cord and rarely the brain (neurogenic shock)
Certain endocrine disorders such as adrenal insufficiency
The mechanisms by which these conditions cause vasodilation vary. For example, a spinal cord injury interrupts the nerves from the brain to the blood vessels that normally cause blood vessel constriction; poisons or toxins released by bacteria can directly cause the blood vessels to dilate.
Symptoms of Shock
Symptoms of shock are similar when the cause is low blood volume or inadequate pumping action of the heart.
The condition may begin with sluggishness, sleepiness, and confusion.
The skin becomes cold and sweaty and often bluish, pale, or ashen.
If the skin is pressed, color returns much more slowly than normal.
Blood vessels may become more visible as a network of lines under the skin.
The pulse is weak and rapid, unless a slow heartbeat is causing the shock.
Usually, the person cannot sit up without feeling light-headed or passing out.
Breathing is rapid, but breathing and the pulse may both slow down if death is imminent.
Blood pressure drops so low that it often cannot be measured with a blood pressure cuff.
Urination decreases and eventually stops.
Eventually, the person may go into a coma and die.
When shock results from excessive dilation of blood vessels, the early symptoms are somewhat different. The skin may be warm and flushed, and the pulse may be strong and forceful (bounding) rather than weak, particularly at first. However, later on, shock due to excessive dilation of blood vessels also produces cold, clammy skin and lethargy.
In the earliest stages of shock, especially septic shock, many symptoms may be absent or may be undetected unless they are specifically looked for. Urine flow may be reduced (because blood supply to the kidneys is reduced), and waste products may build up in the blood. The blood pressure may be low. In older adults, the only symptom may be confusion.
Diagnosis of Shock
Doctor's evaluation
Blood tests
Other tests depending on the probable cause
The diagnosis of shock is based mainly on evidence of organ malfunction found on a doctor's evaluation. For example, people
May have a reduced level of consciousness
May not be producing urine
May have bluish fingers or toes
People may also show signs of trying to compensate for their low blood volume or their heart's inadequate pumping. For example, they may have a rapid heart rate, be breathing rapidly, or be perspiring profusely.
Blood tests can help the diagnosis, but no finding alone is diagnostic, and doctors evaluate each by its trend (ie, worsening or improving) and in light of the person's overall condition.
One blood test (the level of lactate) measures the amount of waste products of cellular activity in the blood. An elevated blood lactate level suggests to the doctor that the organs are not receiving enough oxygen and blood and that the person may have shock.
Blood tests that show a high or low white blood cell count or bacteria or other microorganisms in the blood may help determine that the person has an infection that could be causing septic shock.
Blood tests may also indicate damage to specific organs. For example, a high level of creatinine can indicate that the kidneys are damaged, and a high level of troponin (a cardiac biomarker) can indicate that the heart is damaged.
Other tests are done depending on the probable cause of shock. For example, doctors do cultures of blood and other body fluids if they suspect severe infection. They may also obtain a chest x-ray to look for pneumonia or a computed tomography (CT) scan to look for infections in the abdomen. They may do electrocardiography and other cardiac imaging tests if the person has signs of heart problems.
Treatment of Shock
Calling for help and stopping any bleeding
Intravenous (IV) fluids and/or blood transfusions
Sometimes drugs to help increase blood pressure
Other measures depending on cause
Initial treatment
Most important is to call for help and stop any major bleeding. After doing that, the person can be laid down and kept warm, with the legs elevated.
When emergency medical personnel arrive, they may provide oxygen through a face mask or insert a breathing tube. Fluids may be given by vein (intravenously) at a fast rate and in large volumes to raise blood pressure.
On arrival at an emergency department, the person may be given a blood transfusion if shock is caused by bleeding. Usually, blood is cross-matched before transfusion, but in an emergency when there is no time for crossmatching, type O negative blood can be given to anyone.
If shock is caused by severe infection, doctors give intravenous fluids and antibiotics.
If shock is caused by a heart attack or other heart problem, other procedures or surgery may be needed.
For some types of shock, medications may be given intravenously to increase blood pressure. However, doctors use such medications for as brief a time as possible because they can reduce blood flow to other tissues in the body or cause heart rhythm problems. Medications can increase blood pressure by
Treatment of cause
Fluids given intravenously, blood transfusions, and medications may not be enough to counteract shock if bleeding or fluid loss continues or if shock is caused by a heart attack, infection, or another problem unrelated to blood volume. Treating the cause of shock is vital.
When shock is caused by an inadequate pumping action of the heart, efforts are made to improve the heart’s performance. In addition to fluids and medications, other treatments include percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting if the cause is a heart attack. Surgery may also be needed if the cause is a damaged heart valve or rupture of a wall of the heart. Excess fluid that compresses the heart, a condition called cardiac tamponade, can be removed with a needle or surgery.
When shock is caused by an infection (such as sepsis), treatment of the infection includes antibiotics and removal of the source of infection. When shock is caused by bleeding, surgery may be necessary to stop the bleeding. If shock is caused by an endocrine disorder (such as adrenal insufficiency) or severe allergic reaction (such as anaphylaxis), a corticosteroid may need to be given.
Prognosis for Shock
Untreated shock is usually fatal. If shock is treated, the outlook depends on the
Cause of the shock
Person's age
Other disorders the person has
Presence and severity of any organ failure
Amount of time that passes before treatment begins
Type of treatment given
Multiple organ dysfunction syndrome carries a significant risk of death. The risk of death increases as the number of affected organs increases.
Regardless of treatment, the likelihood of death due to shock after a massive heart attack or due to septic shock, especially in older adults, is high.
