What is sepsis?
Sepsis is the name given to a severe and damaging systemic inflammatory response caused by an infection. The infection may begin at one site of the body and then spread to the blood and possibly to other sites. While the terms bacteraemia and fungaemiarefer to the detectable presence of bacteria or fungi in the bloodstream, sepsis refers to the body's overwhelming response to the infection, which leads to organ dysfunction. (For more on this, see the article on Blood Culture.) The term septicaemia was historically used to describe sepsis with evidence of bacteraemia, but is no longer considered to accurately describe the processes 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 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 (A&E) department. It is more prevalent in newborns and infants and in the elderly but can affect patients of any age. Patients at risk of sepsis include those with trauma, including after major surgery, the presence of invasive medical devices such as catheters, chronic illnesses, and immunocompromised patients.
Sepsis is a major health problem with severe associated morbidity and mortality rates in the range of 25-50%. Comparable figures have been reported for other parts of the world, including the United States and South America.
Normally a person's immune system targets specific threats and limits the response to the area that is infected. With sepsis, a generalised inflammatory response is initiated by the body. 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, 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 last 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 MOF and low blood pressure that is resistant to treatment.
The symptoms that a person experiences depend upon the organs affected, the severity of the condition, and the person's general health status. They may be nonspecific and, in the very young and elderly, may not be typical. Other medical conditions may cause similar symptoms. It is important to quickly distinguish between these conditions as they are treated differently.
Symptoms of sepsis may include:
- Fever (increased body temperature) or coolness (decreased body temperature)
- Chills
- Rapid breathing
- Rapid heart rate
- Fatigue
- Headache
Additional symptoms may indicate a progression to severe sepsis as organs begin to fail. These may include:
- Confusion, mental changes
- Anxiety
- Decreased urine output (kidney dysfunction)
- Abdominal pain
- Nausea and vomiting
- Difficulty breathing, cough
- Chest pain (abnormal function of the heart)
- Pelvic or flank pain
- Mottled skin
Signs and symptoms of septic shock may include those listed above plus a severe drop in blood pressure.
Testing is requested to help diagnose sepsis, distinguish it from other conditions, and to evaluate and monitor the function of the affected person's organs, blood oxygenation, and acid-base balance.
Laboratory Tests
Testing may include:
- Blood culture – to detect microorganisms and evaluate their susceptibility to antimicrobial drugs
- Urine culture and cultures of other body fluids as indicated – to detect the source and type of infection
- FBC (Full blood count) – to evaluate red and white blood cells and platelets
- Lactate – increased levels can indicate organ dysfunction
- Blood gases – to evaluate oxygen in the blood and acid-base balance
- C-reactive protein (CRP) – to detect inflammation in the body
- Procalcitonin – marker sometimes used to distinguish bacterial sepsis from other inflammatory conditions that cause similar symptoms
- Renal profile – to monitor kidney function and electrolyte balance
- Liver function tests – to assess liver status
- Blood glucose – to monitor glucose concentrations
- Prothrombin time (PT) and/or aPTT or other clotting tests to evaluate clotting status
In addition to the tests listed above, CSF analysis may sometimes be requested if it is thought that the person may have meningitis.
Other tests as indicated may be done to help evaluate health status or to rule out other conditions, such as cardiac biomarkers to detect a heart attack.
Non-Laboratory Tests
May be ordered to evaluate organ status, detect complications, and to detect location of infection:
- ECG – to evaluate heart rhythm or injury
- X-ray
- CT (Computed Tomography) scan
- MRI (Magnetic Resonance Imaging)
- Ultrasound scan
Sepsis can have severe clinical consequences (morbidity) and has a high mortality rate. The successful treatment of sepsis depends on early diagnosis and identification of the specific infectious cause. The problem is that patients with sepsis often present, as noted in the previous section, with symptoms that are not specific to sepsis. It is important to begin treatment early and to monitor the person with sepsis carefully. Treatment may begin in the hospital A&E department and is frequently continued and monitored with the person in an ICU. Treatment is focused on addressing the infection, stabilising blood pressure and oxygen supply, restoring acid-base balance, and supporting organ function.
Broad-spectrum antimicrobials are usually given intravenously (IV). Drug therapy may be changed to a more targeted therapy once the microorganism causing the sepsis is identified.
IV fluids are given to help improve and stabilise blood pressure. Sometimes medications are given to constrict blood vessels and increase blood pressure.
Supplemental oxygen may be necessary, and some people require mechanical ventilation to assist with breathing. Other organ support, such as kidney dialysis, is sometimes necessary when organs start to fail.
Surgical procedures are sometimes necessary to remove medical devices such as catheters that may be the source of the infection, to drain abscesses or fluids, to remove and/or fix damaged tissue, and to remove blockages.