Pathophysiology of Septic Shock

ADVANCES IN SEPSIS Vol 1 No 3 2001 87 Definition and epidemiology Septic shock is defined as acute circulatory failure occurring in the presence of severe infection. In essence, this circulatory shock represents an imbalance between the body’s oxygen demands and the available oxygen supply, and is principally of the distributive type, although cardiogenic and hypovolemic components may also be involved. Classically, septic shock is associated with a normal or high cardiac output and a low systemic vascular resistance [1]. Generalized changes in capillary permeability result in edema formation with ‘third spacing’ and altered tissue function. While traditionally associated with bacterial infection, fungi or even viruses can represent the infecting pathogen. Recent studies have indicated a swing in the predominant causative organisms from Gram-negative in favor of Gram-positive bacteria [2]. Sepsis can be the result of infection in many sites, but most commonly involved are the lungs, the abdomen, the urinary tract, and the skin. Pulmonary infection has become an increasingly common source of sepsis [2], perhaps as a result of the widespread, and often prolonged, use of mechanical ventilation, and also the better identification of abdominal sources of sepsis that can be rapidly eliminated.