Multiple Organ Dysfunction Syndrome in Sepsis
Multiple organ dysfunction syndrome (MODS) is a continuum, with incremental degrees of physiologic derangements in individual organs it is a process rather than a single event. Alteration in organ function can vary widely from a mild degree of organ dysfunction to completely irreversible organ failure. The degree of organ dysfunction has a major clinical impact.
In a classic 1975 editorial by Baue, the concept of “multiple, progressive or sequential systems failure” was formulated as the basis of a new clinical syndrome. Several different terms were proposed thereafter (eg, multiple organ failure, multiple system organ failure, and multiple organ system failure) to describe this evolving clinical syndrome of otherwise unexplained progressive physiologic failure of several interdependent organ systems.
Eventually, the term MODS was proposed as a more appropriate description. MODS is defined as a clinical syndrome characterized by the development of progressive and potentially reversible physiologic dysfunction in 2 or more organs or organ systems that is induced by a variety of acute insults, including sepsis.
Sepsis is a clinical syndrome that complicates severe infection and is characterized by systemic inflammation and widespread tissue injury. A continuum of severity from sepsis to septic shock and MODS exists. The clinical process usually begins with infection, which potentially leads to sepsis and organ dysfunction. A consensus panel of the American College of Chest Physicians and the Society of Critical Care Medicine developed definitions of the various stages of this process. Stages of sepsis based on American College of Chest Physicians/Society of Critical Care Medicine Consensus Panel guidelines.
Infection is usually a microbial phenomenon in which an inflammatory response to the presence of microorganisms or the invasion of normally sterile host tissue by these organisms is characteristic. However, viral infections can be indistinguishable from bacteria infections in their presentation. Bacteremia is the presence of viable bacteria in the blood. Systemic inflammatory response syndrome (SIRS) may follow a variety of clinical insults, including infection, pancreatitis, ischemia, multiple trauma, tissue injury, hemorrhagic shock, or immune-mediated organ injury. SIRS is a nonspecific presentation of these insults and is defined by the presence of 2 or more of the following:
Temperature greater than 38.0°C or less than 36.0°C
Heart rate higher than 90 beats/min
Respiratory rate higher than 20 breaths/min or arterial carbon dioxide tension below 32 mm Hg. White blood cell (WBC) count higher than 12,000/µL, lower than 4000/µL, or including more than 10% bands. Sepsis is a systemic response to infection. It is identical to SIRS, except that it must result specifically from infection rather than from any of the noninfectious insults that may also cause SIRS. Sepsis and SIRS are phenotypically similar underscores a common inflammatory pathway causing both.
In early 2016, the Society of Critical Care Medicine and the European Society of Intensive Care Medicine convened a task force to address definitions and clinical criteria for sepsis. The task force concluded that sepsis should be defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Organ dysfunction is represented by an increase in the Sequential [sepsis-related] Organ Failure Assessment (SOFA) score of 2 points or more, which is associated with an in-hospital mortality greater than 10%.
Septic shock is defined as a subset of sepsis in which profound circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone.
Patients with septic shock can be clinically identified by a vasopressor requirement to maintain a mean arterial pressure of 65 mm Hg or greater and serum lactate level greater than 2 mmol/L (>18 mg/dL) in the absence of hypovolemia. This combination is associated with hospital mortality rates greater than 40%.
In out-of-hospital, emergency department, or general hospital ward settings, adult patients with suspected infection can be rapidly identified as being more likely to have poor outcomes typical of sepsis if they have at least two of the following clinical criteria that together constitute a new bedside clinical score termed quick SOFA (qSOFA) respiratory rate of 22/min or greater, altered mentation, or systolic blood pressure of 100 mm Hg or less.
The task force recommended that these updated definitions and clinical criteria should replace previous definitions.
MODS is the presence of altered organ function in an acutely ill patient such that homeostasis cannot be maintained without intervention. Primary MODS is the direct result of a well-defined insult in which organ dysfunction occurs early and can be directly attributable to the insult itself. Secondary MODS develops as a consequence of a host response and is identified within the context of SIRS. The inflammatory response of the body to toxins and other components of microorganisms causes the clinical manifestations of sepsis.
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