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What is sepsis?

Sepsis is the name given to a systemic (widespread) inflammatory response caused by infection, most commonly by bacteria but may also be virus, fungi or protozoa. The infection may begin in one site of the body and then spread to the blood and possibly to other sites. While the term bacteraemia or fungaemia refers to the presence of bacteria or fungi in the bloodstream, sepsis, refers to the response of the body to the infection in the bloodstream. The term septicaemia was historically used to describe sepsis with evidence of bacteraemia, but it is no longer consider to accurately describe the process involved.

Sepsis is a serious condition that can progress from sepsis to severe sepsis and then to septic shock with the failure of one or more organs (multiorgan failure, MOF). Successful treatment often requires intensive care unit (ICU) support. Although sepsis commonly occurs and is identified in hospitalised patients, it can also develop in non-hospitalised patients who may then present to the hospital accident and emergency department. It is more prevalent in newborns and infants and in the elderly. Patients at risk for sepsis include those with chronic or severe illness, who are immunocompromised, have invasive medical devices such as catheters, or trauma (including after serious surgery).

Sepsis is a major health problem. Septicaemia may be fatal in up one in four cases in Australia. Comparable figures have been reported for other parts of the world, including Europe and South America.

Normally a person's immune system targets specific threats and limits the response to the area that is infected. Healthy people can have a temporary bacteraemia after brushing their teeth, as a result of harmless mouth bacteria entering the bloodstream through tiny splits in the gums. These bacteria almost never cause infection and healthy people clear them easily from the bloodstream. With sepsis, a generalised inflammatory response is initiated by the body. This can cause a significant rise or fall in body temperature (fever), increased heart (tachycardia) and respiration (tachypnoea) rates, and a decrease in blood pressure (hypotension). If not treated successfully, as noted above, sepsis can progress to severe sepsis and then to septic shock. 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 leakage can cause fluid build-up in the lungs, thereby reducing 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. With the last stage of sepsis, septic shock, there may be multiple organ failure and low blood pressure that is resistant to treatment.

Last Review Date: December 30, 2018

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