Friday, August 26, 2011

Sepsis, bacteremia and septicemia

There have been several attempts to define sepsis. The various definitions which exist to describe sepsis demonstrate the complexities of the septic process. In general, sepsis can be defined as the systemic host response to infection. It is usually associated with several signs, which include: fever, increased C-reactive protein (CRP), increased heart rate and cardiac output, tachypnea, and increased oxygen consumption among others. However, these may not occur in all patients. Bacteremia can be defined as the presence of viable bacteria in the blood and septicemia is the association of bacteremia with sepsis. Severe sepsis is usually associated with organ dysnfuction, alterations in mental status, coagulation dysfunction and hypoxemia (Vincent, 2002).
Regardless of the definitions used, there is no doubt of the magnitude of the problem, with sepsis affecting some 2-14% of intensive care unit (ICU) admissions, with mortality rates of 35-50%. Aside from the high levels of morbidity and mortality, sepsis is also associated with increased hospital and ICU stays, expensive antimicrobial therapies, and prolonged duration of mechanical ventilation, which all represent a serious economic burden (Vincent, 2002).
The most common isolates in infections causing sepsis are in descending order S.aureus, coagulase-negative Staphylococci, Pseudomonas aeruginosa, Enterobacter, Klebsiella, Acinetobacter, Serratia and Candida (Vincent, 2002). It is thus apparent that Gram-positive organisms can be considered the most important etiological factors for septicemia.
The prognosis of septic patients is influenced not only by the severity of infection, but also by the previous health status and the host response (degree of immunocompetence)(Vincent, 2002). In general, logistic regression or Cox modeling techniques are used to identify those clinical factors that are independently associated with the probability of death (Wax et al., 2002).
Sepsis is a also major health problem in children with high mortality rates. Neonates in particular are at highest risk, especially those with low birth weights. Staphylococci are the most common causes of sepsis in children as well, and are associated with considerable mortality rates (Watson et al., 2003).

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