Vessel injury and capillary leak.

OBJECTIVE: To understand the mechanism of pathologic capillary leak in the critically ill patient. DESIGN: Review of normal and altered physiology of the microvasculature. Review of recent literature describing pathogenesis, mediators, and interventions influencing capillary leak and microvascular repair. SETTING: In vitro and in vivo studies, the latter including animal and human subjects. MEASUREMENTS AND MAIN RESULTS: Capillary leak with resultant edema develops in the critical care setting on the basis of perturbations in Starling's equation, primarily as a result of increased capillary permeability to larger molecules. This process is most likely fueled by inflammatory mediators or mechanical stress. Attempts to prevent or treat this process remain largely unsuccessful; resuscitation is more often symptomatic than therapeutic. Models of microvascular repair focus on discrete injury and may not be applicable to the recovery of capillary damage secondary to a systemic leak CONCLUSIONS: Our understanding of capillary leak syndrome remains fragmented and weighted toward specific mediators contributing to the leak. The implications of extensive edema and the mechanism by which it resolves continue to be the subject of speculation rather than study.