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

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CHAPTER

Sepsis and Septic Shock

syndrome (SIRS), a term in use for decades, is no longer thought well suited for practice by the most recent consensus of international experts (Fig. 27-1). Instead, “sepsis” is now defined as a life-threatening organ dysfunction caused by a dysregulated response to infection. “Septic shock” is the subset of sepsis with circulatory and/or cellular/metabolic dysfunc- tion and higher risk of mortality (Fig. 27-2). The shock state is identified by the need for a vasopressor (e.g., norepinephrine) to maintain a mean arterial pressure greater than 65 mm Hg in the absence of hypovolemia, accompanied by a lac- tate level greater than 2 mmol/L. Moreover, as more has been learned about the pathobiology of the syn- dromes associated with systemic infection, it was thought wise to dissociate the potentially homeo- static responses to infection (e.g., fever, leukocytosis, and tachycardia) from those that reflect the adverse organ response. Prominent among the latter are altered mental status, hypotension, and tachypnea. Whether the shock physiology of sepsis is driven pri- marily by impaired perfusion or by abnormalities of cellular energetics has not been settled. It is likely that causative primacy may depend not only on the individual but on the time point of observation. An operational definition of sepsis is outlined in Table 27-1. EPIDEMIOLOGY The millions of cases of severe sepsis that occur each year across the world present huge medical, social, and economic problems. Severe systemic infections have no age or gender boundaries. With the excep- tion of a spike in frequency in the first year of life, septic shock has a low incidence throughout early adulthood and then an exponentially rising inci- dence, mortality rate, and cost after the age of 50. Although sepsis can develop in perfectly healthy persons, most patients have been hospitalized for several days before recognition of the condition.

• Key Points 1. Sepsis is defined as life-threatening organ dysfunc- tion caused by dysregulated (as opposed to homeo- static) host response to infection. Septic shock is a subset of this condition, with circulatory and/or cel- lular/metabolic dysfunction and higher mortality risk. 2. Septic shock is a common condition that overall car- ries a 30% to 40% risk of death. Outcome is influ- enced strongly by the number and severity of organ system failures that occur. 3. Whereas disordered mental functioning and tran- sient oliguria are almost universal, the lung and circulatory system are the two organ systems that overtly fail with highest frequency. Both manifest dysfunction early in the septic process. Circulatory failure usually reverses within days or proves fatal, whereas respiratory failure often requires 1 to 2 weeks of ventilatory support. Frank renal failure requiring dialysis is unusual. Cognitive function may remain abnormal for months after recovery. 4. Early fluid replacement and vasopressor therapy aimed at restoring adequate perfusion pressure are keystones of circulatory support. Glucocorticoids are a reasonable therapeutic option for patients with shock refractory to vasopressor support. 5. Infection source control, directed cultures, initial broad-spectrum coverage, and targeted antimicro- bial therapy during deescalation phase are essential elements of treating septic shock. TERMINOLOGY Criteria for early recognition of sepsis and septic shock as well as guidelines for best therapeutic approach continue to undergo revision and refinement, perhaps because systemic infection occurs so commonly and with life-threatening consequences unless treated effectively. The term systemic inflammatory response

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