Microvascular dysfunction in sepsis.

The microvascular dysfunction which occurs in sepsis involves all three elements of the microcirculation: arterioles, capillaries, and venules. In sepsis, the arterioles are hyporesponsive to vasoconstrictors and vasodilators. Sepsis also reduces the number of perfused capillaries, thereby impacting on oxygen diffusion to mitochondria. In the venules of some tissues (e.g., mesentery) there is an inflammatory response characterized by neutrophil infiltration and protein leakage. In addition, PMN-endothelial adhesive interactions occur in precapillary microvessels and capillaries in organs, such as, the lung and heart. Thus, all these elements of the microcirculation are involved in the sepsis-induced inflammation. In this review we address emerging views on the mechanisms involved in the microvascular dysfunction induced by sepsis within the framework of these three basic elements of the microcirculatory unit.