Sepsis is a serious bodywide response to bacteremia or another infection. Septic shock is life-threatening low blood pressure (shock) due to sepsis.
Usually, the body's response to infection is limited to the specific area infected. But in sepsis, the response to infection occurs throughout the body—called a systemic response. This response includes an abnormally high temperature (fever) or low temperature (hypothermia) plus one or more of the following:
As sepsis worsens, organs begin to malfunction and blood pressure may decrease. Sepsis is considered severe if organs malfunction. Septic shock is diagnosed when blood pressure remains low despite intensive treatment. In the United States, about 90,000 people, usually those who are hospitalized, die of septic shock each year.
Sepsis occurs when toxins produced by the bacteria cause cells in the body to release substances that trigger inflammation (cytokines). Although cytokines help the immune system fight infection, they can have harmful effects:
These effects lead to a series of harmful complications:
All of these effects result in a vicious circle of worsening organ malfunction:
Blood clots continue to form, using up the proteins in blood that make up clots (clotting factors). Then, excessive bleeding may occur.
Most often, sepsis is caused by infection with certain kinds of bacteria, usually acquired in a hospital. Rarely, fungi, such as Candida, cause sepsis. Infections that can lead to sepsis begin most commonly in the lungs, abdomen, or urinary tract. In most people, these infections do not lead to sepsis. However, sometimes bacteria spread into the bloodstream (a condition called bacteremia). Sepsis may then develop. If the initial infection involves a collection of pus (abscess), the risk of bacteremia and sepsis is increased. Occasionally, sepsis is triggered by toxins released by bacteria, rather than from bacteria entering the bloodstream (bacteremia).
The risk of sepsis is increased in people with conditions that reduce their ability to fight serious infections. These conditions include the following:
The risk is also increased in people who are more likely to have bacteria enter their bloodstream. Such people include those who have a medical device inserted into the body (such as a catheter inserted into a vein or the urinary tract, drainage tubes, or breathing tubes). When medical devices are inserted, they can move bacteria into the body. Bacteria may also collect on the surface of such devices, making infection and sepsis more likely. The longer the device is left in place, the greater the risk.
Other conditions also increase the risk of sepsis:
Most people have a fever, but some have a low body temperature. People may have shaking chills and feel weak. Other symptoms may also be present depending on the type and location of the initial infection. Breathing, heart rate, or both may be rapid.
As sepsis worsens, people become confused and less alert. The skin becomes warm and flushed. The pulse is rapid and pounding, and people breathe rapidly. People urinate less often and in smaller amounts, and blood pressure decreases. Later, body temperature often falls below normal, and breathing becomes very difficult. The skin may become cool and mottled or blue because blood flow is reduced. Reduced blood flow may cause tissue, including tissue in vital organs (such as the intestine), to die, resulting in gangrene.
When septic shock develops, blood pressure is low despite treatment.
With treatment, the risk of death is about 15% for people with sepsis and 40% or more for people with septic shock.
Doctors usually suspect sepsis when a person who has an infection suddenly develops a very high or low temperature, a rapid heart or breathing rate, or low blood pressure. To confirm the diagnosis, doctors look for bacteria in the bloodstream (bacteremia), evidence of another infection that could be causing sepsis, and an abnormal number of white blood cells in a blood sample.
Samples of blood are taken to try to grow (culture) the bacteria in the laboratory—a process that takes 1 to 3 days. However, if people have been taking antibiotics for their initial infection, bacteria may be present but not grow in the culture. Sometimes catheters are removed from the body, and the tips are cut off and sent for culture. Finding bacteria in a catheter that had contact with the blood indicates that bacteria are probably in the bloodstream.
To check for other infections that may cause sepsis, doctors take samples of fluids or tissue, such as urine, cerebrospinal fluid, tissue from wounds, or sputum coughed up from the lungs. These samples are cultured and checked for bacteria. Imaging tests may also be done.
Other tests are done to look for signs of organ malfunction and other complications of sepsis. They may include the following:
Sepsis and septic shock must be treated immediately with antibiotics—even before test results confirm the diagnosis. A delay in antibiotic treatment greatly decreases the chances of survival. People with symptoms of septic shock are immediately admitted to an intensive care unit for treatment.
When choosing the initial antibiotics, doctors consider which bacteria are most likely to be present, which depends on where the infection started. Often, two or three antibiotics are given together to increase the chances of killing the bacteria, particularly when the source of the bacteria is unknown. Later, when the test results are available, doctors can substitute the antibiotic that is most effective against the specific bacteria causing the infection.
If present, abscesses are drained, and catheters or other medical devices that may have started the infection are removed. Surgery may be done to remove dead tissue.
People with septic shock are also given large amounts of fluid intravenously to increase the amount of fluid in the bloodstream and thus increase blood pressure. Drugs, such as dopamine or norepinephrine (which cause blood vessels to narrow), may be needed to increase blood flow to the brain, heart, and other organs. Oxygen is given through a mask, through nasal prongs, or, if a breathing (endotracheal) tube has been inserted, through that tube. If needed, a mechanical ventilator is used to help with breathing.
Last full review/revision September 2008 by Lowell S. Young, MD