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What is sepsis?

Sepsis is the body's systemic inflammatory response to a bacterial infection. Sepsis is serious, overwhelming, and sometimes life-threatening. An infection may begin in one site of the body and then spread to the blood (bacteremia) and possibly to other sites. For example, a urinary tract infection may spread from the bladder and/or kidneys into the blood and then be carried throughout the body, infecting other organs.

The term septicemia is sometimes used to describe this condition. While the term septicemia refers to the presence of disease-causing organisms like bacteria in the bloodstream, sepsis refers to the body's overwhelming response to the infection.

Normally, a person's immune system targets a specific threat such as bacteria and limits its response to the infected area. With sepsis, the body initiates a generalized inflammatory response. This can cause a significant rise or fall in body temperature, increased heart and respiration rates, and a decrease in blood pressure. If not treated successfully, sepsis can progress to severe sepsis.

As the condition progresses to severe sepsis, the amount of oxygen that is carried to tissues and organs decreases, blood clots can form in the capillaries, and fluids can leak from the blood into tissues. This can cause fluid build-up in the lungs and reduce respiratory function. Overall, the body's acid-base balance becomes disrupted, circulation is impaired, waste products begin to accumulate, tissues are damaged, and organs such as the lungs, kidneys, and liver begin to fail. In the last stage of sepsis, septic shock, there may be multiple organ failure (MOF) and low blood pressure that is resistant to treatment.

Although sepsis occurs in hospitalized patients, most people who develop the reaction do so outside the hospital and may seek care in a hospital emergency room. According to the Centers for Disease Control and Prevention, about 70% of people who develop sepsis outside the hospital have used health services recently or have a chronic condition that requires frequent medical attention. It is more prevalent in newborns and infants and in the elderly. Other people at risk for sepsis include those with trauma (for example, after surgery), those with invasive medical devices such as catheters, those with chronic illnesses, and people with weak immune systems (immunocompromised).

Sepsis is a major health problem. In the U.S., mortality rates due to sepsis range from 25-50%. Comparable figures have been reported for other parts of the world, including Europe and South America.

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