Description Medical Heart Failure and Shock

Septic shock is a clinical syndrome associated with severe systemic infection. It is a sepsis-induced shock with hypotension despite adequate fluid replacement. Patients have perfusion

838 Septic Shock abnormalities, including lactic acidosis, oliguria (urine output <400 mL/day), or an acute alteration in mental status. Often septic shock is characterized by decreased organ perfusion, hypotension, and organ dysfunction. Septic shock is the major cause of death in intensive care units; the mortality rate is as high as 50% to 80% depending on the patient population. The incidence has increased during the last 50 years in North America probably owing to an increased number of patients who are immunocompormised, the increased use of invasive devices, and a longer life span for the elderly. It occurs in 2 cases per each 100 hospital discharges, and approximately 70% of the patients who develop septic shock need intensive care.

Septic shock is part of the continuum associated with the systemic inflammatory response syndrome (SIRS), defined by two or more changes in the following four factors: body temperature, heart rate, respiratory function, and peripheral leukocyte count. Sepsis, on the other hand, is defined as systemic host response to infection with SIRS plus a documented infection, and severe sepsis is defined as sepsis with hypotension, despite fluid resuscitation, and evidence of inadequate tissue perfusion.

The syndrome usually begins with the development of a local infectious process. Bacteria from the local infection enter the systemic circulation and release toxins into the bloodstream. Gram-negative bacteria release endotoxins from their cell membrane as they lyse and die, whereas gram-positive bacteria release exotoxins throughout their life span. These toxins trigger the release of cytokines (proteins released by cells to signal other cells) such as tumor necrosis factor and the interleukins (ILs). They also activate phagocytic cells such as the macrophages. The complex chemical reactions lead to multiple system effects. As the syndrome progresses, blood flow becomes more sluggish, tissues become hypoxic, and acidosis develops. Ultimately, major organ systems (such as the lungs, kidneys, liver, and blood coagulation) fail, which leads to multiple organ dysfunction syndrome.

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