Figure 1.

Acute and chronic immune changes after hemorrhage. After hemorrhage, a hyperinflammatory response known as the systemic inflammatory response syndrome (SIRS) occurs. This response triggers an immune suppressing response known as the compensatory anti-inflammatory response syndrome (CARS). These changes occur early after injury and lead to multiorgan dysfunction and early infections. For many patients, these responses resolve, and immune homeostasis is restored; however, in many patients, homeostasis is never restored, and they develop persistent inflammatory–immunosuppressive and catabolic syndrome (PICS). PICS can persist for months, leading to persistent organ dysfunction, opportunistic infections, and death.