Critical Care Medicine 978-1-4963-0291-5 chapter 27

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SECTION II • Medical and Surgical Crises

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20 Mortality Rate (%)

FIGURE 27-5. Relationship between mortality and the number of organ systems failing because of sepsis. Each additional failing organ system raises the overall mortality rate by 15% to 20%.

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Number of Organ Failures

ORGAN SYSTEM FAILURES In fatal cases of sepsis, it is the cumulative effects of organ system failures that cause patients to suc- cumb. Therefore, understanding the usual onset, duration, and resolution of organ failure and meth- ods of support assumes paramount importance. A clear relationship exists between the number of organ failures and mortality. Each new organ system failure adds roughly 15% to 20% to the baseline risk of death for all ICU residents (Fig. 27-5). Septic patients in the ICU typically average two to three failing organ systems at the time of diagnosis. The frequency of various organ failures noted at the time of diagnosis is shown in Figure 27-6. The most com- mon constellation is the development of pulmonary dysfunction and shock. (Most patients develop-

ing shock also will be oliguric at least transiently.) Despite the multiplicity of causes, the pattern of organ failures in sepsis is remarkably similar among patients, with lung and circulatory failure devel- oping rapidly (usually within 72 hours). Advanced central nervous system (CNS) dysfunction tends to develop later, although confusion is often the predominant manifestation of severe sepsis in the elderly. Oliguria is extremely common in the early stages of sepsis of whatever severity and does not always signal advancing kidney injury before resus- citation has been completed. Even though coagu- lation abnormalities exist in almost all victims of life-threatening sepsis, overt disseminated intra- vascular coagulation (DIC) occurs in only 10% to 15%, and its timing and its clinical recognition are unpredictable.

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Percent with Organ Failure

FIGURE 27-6. Prevalence of organ system failures at the time of diagnosis of severe sepsis. ARDS, acute respiratory distress syndrome; CNS, central nervous system.

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Oliguria

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