Biology of Coagulation and Coagulopathy in Neurologic Surgery

Hemostasis is a cell-based process that is regulated in a tissue-specific manner by the differential expression of procoagulant and anticoagulant factors on endothelial cells from different sites throughout the vasculature. The central nervous system, in particular, exhibits unique mechanisms of hemostatic regulation that favor increased activity of the tissue factor pathway. This results in an unusually high degree of protection against hemorrhage, at the potential expense of increased thrombotic risk. Unfortunately, standard laboratory assays, including the PT and aPTT, do not accurately reflect the complexity of hemostasis in vivo; therefore, they cannot predict the risk of bleeding or thrombosis.