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Ebook Harrison's pulmonary and critical care medicine (2nd edition): Part 2

(BQ) Part 2 book "Harrison's pulmonary and critical care medicine" presents the following contents: Common critical illnesses and syndromes, disorders complicating critical illnesses and their management, laboratory values of clinical importance. | SECTION IV COMMON CRITICAL ILLNESSES AND SYNDROMES CHAPTER 28 SEVERE SEPSIS AND SEPTIC SHOCK Robert S. Munford DEFINITIONS See Table 28-1 Animals mount both local and systemic responses to microbes that traverse their epithelial barriers and enter underlying tissues. Fever or hypothermia leukocytosis or leukopenia tachypnea and tachycardia are the cardinal signs of the systemic response that is often called the systemic inflammatory response syndrome SIRS . SIRS may have an infectious or a noninfectious etiology. If infection is suspected or proven a patient with SIRS is said to have sepsis. When sepsis is associated with dysfunction of organs distant from the site of infection the patient has severe sepsis. Severe sepsis may be accompanied by hypotension or evidence of hypoperfusion. When hypotension cannot be corrected by infusing fluids the diagnosis is septic shock. These definitions were developed by consensus conference committees in 1992 and 2001 and have been widely used there is evidence that the different stages may form a continuum. ETIOLOGY Sepsis can be a response to any class of microorganism. Microbial invasion of the bloodstream is not essential since local inflammation can also elicit distant organ dysfunction and hypotension. In fact blood cultures yield bacteria or fungi in only 20 40 of cases of severe sepsis and 40 70 of cases of septic shock. Individual gram-negative or gram-positive bacteria account for 70 of these isolates the remainder are fungi or a mixture of microorganisms Table 28-2 . In patients whose blood cultures are negative the etiologic agent is often established by culture or microscopic examination of infected material from a local site specific identification of microbial DNA or RNA in blood or tissue samples is also used. In some case series a majority of patients with a clinical picture of severe sepsis or septic shock have had negative microbiologic data. EPIDEMIOLOGY Severe sepsis is a contributing factor in 200 000 deaths