Sepsis refers to a whole body inflammatory response to serious infection (systemic inflammatory response syndrome [SIRS]). It is a complex and sometimes rapid process that results when disease-causing organisms (pathogens), usually bacteria and the chemicals they produce (bacterial toxins), are introduced into the bloodstream (bacteremia) either directly or from another source of infection. This triggers the body's release of pro-inflammatory mediators (i.e., cytokines or endotoxins such as tumor necrosis factor [TNF] and interleukin-1 [IL-1]) and anti-inflammatory mediators (i.e., leukotrienes, histamine, and serotonin) to control this overwhelming systemic infection. In rare cases, fungi and viruses also can cause sepsis. The widespread presence of the causative organisms and the pro- and anti-inflammatory mediators released by the body to fight them results in a septic inflammatory state (septicemia), that includes blood vessel dilation, leakage of fluid into tissues, coagulation abnormalities, and, initially an increase in cardiac output, followed by an eventual decline in cardiac output. Blood pressure may then drop severely (septic shock), and tissue throughout the body is deprived of blood and oxygen, resulting in ischemia, cell damage, and multiple organ failure, including failure of the heart, liver, lungs, brain, and kidneys. Failure of any of these organs can be fatal. Even with modern therapeutic measures, septic shock is fatal in 10% to 80% (average 40%) of all cases (Weil).
The most common pathogens responsible for sepsis and septic shock are gram-negative bacteria and gram-positive cocci (staphylococci and meningococci). Sepsis may result when pathogens enter the bloodstream from puncture wounds, deep cuts, burns, infected surgical incisions, gangrene of bowel or any tissue, acute pancreatitis, major trauma, or the use of intravenous lines and invasive devices such as indwelling vascular or urinary catheters, endotracheal tubes, post-operative drainage tubes, ostomy devices and tubing and extended use of corticosteroid drugs or antibiotics. In most cases, the infection is hospital-acquired. Sepsis is potentially fatal, especially in the elderly whose already compromised systems are more susceptible to septic shock.Incidence and Prevalence: The incidence of sepsis has been increasing for the past 30 years because of the increased use of intravascular catheters and other invasive devices, widespread use of immunosuppressive drugs, an increase in HIV infection/AIDS, and the emergence of antibiotic-resistant organisms. Medical has increasingly prolonged the life of individuals with cancer, diabetes, and AIDS, thus increasing the incidence of infection, which also increases the incidence of sepsis.
The incidence of sepsis, severe sepsis, and septic shock in the US is recorded separately: sepsis is diagnosed in 400,000 individuals annually, resulting in about 60,000 deaths; severe sepsis with organ failure affects 300,000 individuals annually, resulting in another 60,000 deaths; and septic shock (severe sepsis with significant hypotension) occurs in 200,000 individuals, resulting in 90,000 deaths annually (Weil). One large study prior to 2003 estimated that in the US, there are more than 750,000 cases of sepsis annually (Cohen 614). More recent estimates indicate about 900,000 cases are diagnosed annually, of which about one-third progress to organ failure and septic shock (Weil). |