The role of the microcirculation in the multi-organ dysfunction syndrome

The systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS) are significant causes of morbidity and mortality in the intensive care unit. The pathogenesis of MODS is poorly understood; however, endotoxin (LPS) and cytokines (for example interleukins, tumor necrosis factor and platelet activating factor) are thought to play a major role by inducing microvascular injury. A crucial step in the normal functioning of the immune system is the adhesion of cells to each other and, via extravasation, penetration of the extracellular matrix. This is an essential process for normal host defence against injury and infection. In SIRS this process becomes uncontrolled, leading to extravasation of neutrophils causing tissue injury and inflammation. In addition there is increased capillary permeability. It is this disturbance of the microcirculation that is responsible, either wholly or in part, for the development of SIRS and MODS.