Vascular hemostasis in flowing blood in children

This review considers differences in hemostasis among newborns, children, a nd adults from the standpoint of the vascular endothelium and, where approp riate, in the presence of flowing blood. Special procoagulant features of n ewborn hemostasis include unusually large von Willebrand factor multimers, augmented platelet transport under flow conditions, and greater ability of newborn endothelium to generate tissue factor. Special anticoagulant featur es in the newborn include increased vessel wall glycosaminoglycan activity, elevated alpha(2)-macroglobulin, and increased percentage of free protein S, The net effect of the differences is that hemostasis is generally achiev ed in all age groups but is developmental in nature. In addition to congeni tal hypercoagulable states and catheter placement, developmental vascular a nomalies appear to constitute a thrombotic risk, at least in some children (and possibly adults).