Microvascular alterations in thrombin-induced experimental disseminated intravascular coagulation in the dog

Disseminated intravascular coagulation is often characterized by organ failure and bleeding. By use of light microscopy, previous studies have shown extensive fibrin deposition in vessels. However, quantification of fibrin deposition using ultrastructural methods has not been reported. In this study dogs were infused with thrombin, and disseminated intravascular coagulation developed. Using a blinded morphometric analysis method, we observed deposition of fibrin in nearly half of the microvascular vessels. Such deposition probably accounts at least for part of the organ dysfunction. Almost half the vessels also had altered endothelial structure including thinning of the endothelial membrane, formation of extremely thin spots, fenestrations, and even a few ruptured areas. These findings at least in part explain the extravasation of blood in disseminated intravascular coagulation.