Sepsis,a septic shock, and the systemic inflammatory response syndrome are interrelated and somewhat overlapping conditions. The definitions that follow are based on The Third International Consensus Definitions for Sepsis and Septic Shock (2016):
- Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection.
- Septic shock is defined as a subset of sepsis in which particularly profound circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone.
- Systemic inflammatory response syndrome (SIRS) is a sepsis-like condition associated with systemic inflammation that may be triggered by a variety of nonmicrobial insults, such as burns, trauma, and/or pancreatitis. Pathogenic feature common to SIRS and septic shock is a massive outpouring of inflammatory mediators from innate and adaptive immune cells that produce arterial vasodilation, vascular leakage, and venous blood pooling. With the advent of chimeric antigen receptor T-cell (CAR-T) therapy, a similar iatrogenic syndrome called cytokine release syndrome has been observed in cancer patients. The cardiovascular abnormalities associated with SIRS result in tissue hypoperfusion, cellular hypoxia, and metabolic derangements that lead to organ dysfunction and, if severe and persistent, organ failure and death.