The term sepsis describes a spectrum of pathophysiologic responses to infection. In the setting of advanced antibiotic therapies, sophisticated respiratory and cardiovascular support, and improved diagnosis, sepsis-associated mortality has declined in recent years, though it remains greater than 50% in some groups. Early recognition and aggressive management are critical to reducing morbidity and mortality.
The causative organisms implicated in sepsis have changed over time, and many cases have nondiagnostic or negative cultures. The identified sites of primary infection are predominantly lung (47%), followed by unknown/other (28%), peritoneum (15%), and urinary tract (10%). Prior to 1987, gram-negative organisms were the predominant organisms identified. In the past 20 years, however, sepsis caused by gram-positive organisms has increased markedly, and gram-positives are now the predominant etiologic agents. Additionally, over the same time period, the incidence of fungal sepsis has increased by over 200%. These changes likely reflect the increased numbers of immunocompromised patients and debilitated surgical patients, and the increased use of indwelling catheters and devices.
The American College of Chest Physicians and the Society of Critical Care Medicine have developed standardized diagnostic criteria for sepsis, severe sepsis, and septic shock to describe the continuum of evolving physiologic derangement (Table 61.1). Categorization of patients in this system provides vital prognostic information and guides critical disposition and treatment decisions.